dcmodels

The following discusses the Acura TSB 11-031, mentioned by user jack1454 in post #49 in the link:
https://acurazine.com/forums/showthread.php?t=856420&page=2

The standard RDX OEM A/C compressor clutch-relay, has been known to fail early. There is currently an OEM upgraded, more ‘robust’ replacement relay. Read the following, to decide if you also wish to upgrade any of the other relays.

SYMPTOM: the battery dies after the vehicle is parked for a short time or overnight, or the A/C system blows warm air, or both. Also, the A/C compressor may be noisy and may [ed: be] emitting refrigerant vapor from the relief valve.

NOTE: if the only symptom is a dead battery, it may occur intermittently.

PROBABLE CAUSE: the A/C compressor clutch relay may be stuck closed. If the relay sticks [ed: closed] when the ignition switch is turned to LOCK (0), and the compressor was running, it creates enough parasitic draw to discharge the battery. If the relay sticks [ed: closed] while the engine and A/C are running at a lower vehicle speed, the A/C pressure may spike, causing the compressor’s relief valve to open and lose refrigerant.

WHAT TO DO:
The above (blue text) is quoted from Acura TSB 11-031 for the 2007-2011 MDX (all), March 2, 2012. Both my local Acura dealers state that some older RDX models have displayed this same problem.

Replace the existing A/C compressor clutch relay with the upgraded part, to prevent future problems. However, if a problem has already occurred, then check with your dealer, or read the TSB for proper corrective measures. In particular, check for possible Freon loss, by looking at the compressor relief valve.

Please use the following information as a reference only. See your Acura/ Honda parts dealer and verify all information, for your own specific year and model of RDX. Different years of the RDX were delivered with different relays. You may already have the upgraded relay, if you have a late model RDX, but only in the A/C compressor clutch circuit.

Your local Acura/ Honda dealer may, or may not, be aware of the upgraded relay. At present, the upgraded relay is only being recommended by Acura for the A/C compressor clutch electrical circuit. According to my local Acura dealer, this recommendation is now for all Acura models, including the RDX, not just the MDX, as indicated in TSB 11-031.

PART NUMBERS for the OLD RELAY and REPLACEMENT UPGRADED RELAY
The original part number is 39794-SDA-A03 manufactured by OMRON in the USA

The upgraded replacement part number is 39794-SDA-A05 manufactured by MITSUBA in Vietnam. As best I can tell, this upgraded relay has been used across all of the Honda/ Acura model lines for the past 3 model years, so that it is unlikely that the new part number will cause any problems itself.

The approximate price (as of the date of this post) for the original relay is $6, and the upgraded relay price is $30. Please look carefully at the almost exact same part numbers for the two different relays – only the very last digit of the two part numbers differ. Check the manufacturer also when purchasing, to help you get the correct replacement part.

NOTE: the old/ OEM A/C clutch relay part number, is still used for several other electrical circuits – so again, check that you are purchasing the correct part number, for the upgraded A/C clutch relay.

WHAT HAPPENS WHEN THE A/C CLUTCH RELAY FAILS?
Please read the MDX TSB 11-031 for details. However, the short answer is that either the battery dies when the vehicle is parked overnight, and/ or the A/C compressor pressure relief valve vents the Freon, and the A/C stops delivering cold air.

Low Freon can lead to a failed A/C compressor, with costly consequences. The A/C compressor may require replacement, as well as other parts of the A/C system. This failure may *not* be covered by warranty.

LIST OF ALL ELECTRICAL CIRCUITS using the SAME A/C CLUTCH RELAY
The electrical circuits in the list below, all use the same OEM relay as the A/C compressor clutch, at least for the older years RDX. Do note that the later RDX models, already have the “new” OEM upgraded A/C clutch relay, as factory delivered. You will want to check your own RDX model, to verify which relay is actually in your vehicle.

This list is provided to help you replace the correct relay in the A/C clutch circuit. The following relay reference location numbers, are the numbers used for the 2007-2009 RDX factory parts diagram. I believe that all of the first generation RDXs use the same diagram. However, it would be safer to check and purchase any relay, by function name, and by looking at the diagram on the primary underhood fuse/ relay box cover, or by looking at the picture in the FSM (factory service manual), or by consulting with your dealer parts person.

3) A/C condenser Fan

4) Electronic Throttle Control System (ETCS) control

5) Radiator Fan

6) A/C compressor clutch

7) PGM-FI (programmed fuel injection) sub-relay

NOTE: relays 8-11 are already upgraded, maybe, certainly they are more expensive, $30-40 each.

WHAT IS THE PROBLEM WITH THE EXISTING/ OLD A/C CLUTCH RELAY?
Or, why don’t the other four (4) exact same relays, in different circuits, fail early? Or at least, why do the other four relays last much longer than the clutch relay? I can only guess that Honda simply specified an improper relay for the A/C clutch circuit, based on the following . . .

The RDX A/C compressor electromagnetically operated clutch, is a different type of load (inductive) than that of the other RDX electrical circuits (which use the exact same relay). Long-term arc generation at the relay contact points, typically occurs in a solenoid (inductive) type load (magnetic clutch), leading to eventual fusing (welding) of the contact points. There is an interesting technical article concerning a patent for a better relay for use in this type of circuit:
http://www.freepatentsonline.com/6791045.html

Also, operation of a vehicle air-conditioner has undergone various changes in recent years. Previously, vehicle air-conditioners were usually operated only in summer. However, now air-conditioners are operated throughout the year as automatically-controllable air-conditioners. Consequently, operational frequency and the operation period of relays and switches to control the air-conditioner (compressors) has increased correspondingly.

The upgraded Honda/ Acura RDX clutch relay is the same size as the old one – but I assume that the relay contact material is different – with a higher capacity (current) rating, and a longer rated service life.

ADDITIONAL INFORMATION:
Please see the following links for more information – the sticking A/C clutch relay is a common problem for both the RDX and the TL as well as the MDX. These links may give you some information to help you determine if you have a similar or the same problem.

LINK: non RDX A/C operation, caused by failed clutch relay
https://acurazine.com/forums/showthread.php?t=856420

LINK: DIY diagnosis and replacement of RDX worn and failing A/C compressor field coil (which also requires removal of the clutch for access to the field coil). Also discusses applicable FUSE numbers.
https://acurazine.com/forums/showthread.php?t=862720

LINK: TSB 11-031: MDX upgraded A/C clutch relay, symptom of Dead Battery and/ or A/C Cools Poorly
https://acurazine.com/forums/showthread.php?t=728064

LINK: RDX frequent dead battery – see post #2, #12, and #14
https://acurazine.com/forums/showthread.php?t=887469

LINK: Air [ed: A/C] compressor constantly engaged, even when car is turned off.
https://acurazine.com/forums/showthread.php?t=885161

LINK: No AC + "Hissing" noise under dash = Bad evaporator? – actually it was a sticking A/C clutch relay, the hissing was the Freon venting – see post #8 for the resolution of problem
https://acurazine.com/forums/showthread.php?t=867530


SHOULD YOU UPGRADE ANY RELAY OTHER THAN THE A/C CLUTCH RELAY?
NO - You SHOULD NOT also upgrade the other four OEM RDX nnn-A03 relays, that are the same as the A/C clutch relay, as listed above in a previous section, using the upgraded Honda nnn-A05 relay.

According to the Acura FSM (factory service manual), each RDX underhood relay uses an internal protective circuit – either a resistor or a diode. I cannot determine whether the original A03 or the upgraded A05 relay, uses the resistor or the diode. Any replacement relay should (probably) use the same type of protective circuit – unless of course, as in the case of the A/C clutch relay, the replacement relay has been specifically chosen by Acura/ Honda.

Maybe the A05 upgraded relay would work properly in the other four RDX A03 relay circuits, as well as in the A03 A/C clutch circuit – and maybe it would not.

SHOULD YOU REPLACE ANY RELAY EARLY – BEFORE FAILURE?
Understand that a relay is a wear item, and is intended to eventually be replaced, just like brake pads and other wear items. Note that relay service-life is (primarily) measured in ON/ OFF cycles, not in vehicle miles or years. That means that the life of a relay is determined by how many times the device controlled by the relay, is cycled ON/ OFF (by the relay), such as the A/C compressor clutch or Radiator Fan motor – not by the number of miles the vehicle has been driven.

However, you may wish to simply replace those other four relays, with the same original-type relay, sooner than 10 years. Just keep in mind what those relays are controlling. Do you really want the radiator fan-relay to fail to run the fan motor, someday during your 110 degree city traffic commute? Do you really think that you would notice a problem, before the engine overheated?

Remember, just because the A/C clutch relay typically fails CLOSED, most relays fail OPEN. Meaning, the radiator fan relay will *not* run the fan motor, when it fails, causing the engine to overheat.

HOW OFTEN/ SOON SHOULD YOU REPLACE ANY RELAY?
The nnn-A03 relay discussed in this post is an OMRON G8HL-H71 micro ISO low profile, with a service life of a minimum of 100K cycles, as best as I can determine from the OMRON web site, technical data.

Both the A/C condenser fan motor and radiator fan motor, cycles at the same rate as the A/C compressor clutch. That is a simple check for proper operation of the A/C system.

Under certain conditions, it would be possible for the A/C system condenser fan motor relay, type nnn-A03, to reach and exceed its service life in only 5-6 years, or less.

But as they say, your mileage may vary. When the ambient temp is 60 degrees, and my A/C is in AUTO mode, at engine idle the A/C clutch and radiator fan motors cycle every 10 seconds. That would be 360 cycles every hour. If the A/C really cycled like that all of the time, the fan relay(s) would reach its service life of 100K cycles, in less than 1-year. Of course, the A/C fan does not cycle that quickly all of the time. But really, it does explain why the A/C clutch itself and the controlling relay do not last forever – or more to the point, why they only last a few years.

However, under average conditions, we should expect 10-12 years as a service life for most relays. If you drive 10K miles per year, mostly city driving or commuting, at an average speed of 25mph (check your MID), then your RDX operates for about 400 hours per year. When left in AUTO mode, the HVAC system does run the A/C compressor during cooler weather, which means that the compressor runs year-a-round. And if the A/C condenser fan motor cycles about every 3 minutes, then the controlling relay in that circuit would cycle 20 times per hour, or 8 thousand times per year, depending upon the weather in your location. So the relay would reach its service life in about 12 years, for this example.

By observing your own A/C system, or other electrical systems, you should be able to determine how often to replace your own relays, before failure. I plan to replace these four nnn-A03 relays every 5-years, or 50K miles.

CAUTIONS WHEN REPLACING A RELAY
Do not drop the relay. Do not use a relay that has been dropped. The upgraded OEM Honda/ Acura relay is factory sealed inside a bubble wrap package, for shock and static electrical protection.

Just like any electronic/ electrical part, every so often you get a defect. The odds of a defect are small (tiny), but I recommend that you do not replace a relay, and immediately start on a 1,000 mile trip. An electrical engineer would recommend a *burn-in* period – I suggest 10 hours.

That is, replace your relay(s), one or more, and keep an eye on things for the first 10 hours of operation. Verify that all components in the circuit powered by the new relay, are functioning correctly. For the A/C clutch relay, it just means check that the compressor clutch actually operates when the A/C system is turned on, using the vehicle interior HVAC controls.

Electronic parts are *funny*, because they either fail quickly, or they last a very long time.

REMOVING A RELAY
Probably most people just use needle-nose pliers to remove the relays. This can damage the relay, but if you are going to replace it anyway . . .

Honda does make a special relay puller, which sells for only $6. But the company which actually manufacturers the puller, has refused to sell the puller in quantities of less than 10-at-a-time. If you really want to spend $50-60 for this puller, its p/n 07AAC-000A1A0, which is just a stamped and bent piece of metal.

The service manager at my Acura dealer, who had to purchase 10 pullers for himself, for dealer-shop use, gave me one of them for my own use. I used the Honda puller to pull and replace all 5 relays discussed in this post.

For everyone else, the only other consumer relay puller of which I am aware, is the one made and sold by LISLE. Actually, I have no idea who actually makes this puller, but it is sold by a larger number of different places under many different manufacturer names. The price ranges from $13 online to around $25 at NAPA.

The LISLE part number is 469-50. Note that I have never used this puller, but currently do have one on special-order, for use in my Chevy. I believe that it will also work on a Honda relay, and most other vehicle relays.

GM sells a relay puller through its dealers for about $70-80, and perhaps other car manufacturers also have their own relay puller. Anyone know of perhaps a Toyota or Nissan or ?? cheap but good relay puller.

INSTALLING A RELAY
Place a smear of dielectric grease on each side, of each relay connector (lug/ pin), orient the relay correctly (using the projection on the side), and press the relay straight and fully into the socket. The grease is to prevent oxidation of the relay connectors. I used the side of the paper rod of a Q-tip to apply the dielectric grease. Wipe off any excess. Do *not* use the cotton swab-tip, as any cotton fibers may cause a short circuit.

While I did not detect any original grease on the OEM relays that I removed, I did note tiny traces of grease around the area of the relay sockets.

CHEERS.

PICTURE: underhood relay positions

737 Jock

Thanks dcmodels, for an excellent, highly informative post.

At 120k, the AC on our 2007 is getting weak. I'm going to start with the relays and then consider the compressor clutch repair.

dcmodels

You are welcome - and I would certainly be interested in what you measure as your own A/C Clutch clearance, whether or not you decide to replace the clutch. I plan to measure my own, at 36K miles, as a reference for later - wish I had known to do that at an earlier mileage, so that I could estimate the rate of wear.

As for your A/C getting 'weak', I do not believe that the relays could affect that - they either work or don't work, and just shunt the power to the clutch, fan motors, etc. The only reason to replace them is as a preventative measure, to prevent failure at an inoportune time.

I suppose if the clutch is not completely engaging, i.e., sort of slipping, then the A/C output would suffer. But that also seems unlikely to me. I would guess that once the clutch starts to slip, it would not last long, and the sort of problems stated in the TSB 11-031 would occur within a short time.

Just a guess, of course, but its more likely that either the Freon is getting 'low', or else the efficiency of the compressor is decreasing. Freon charge level is easy to check (well, not for me, but for a dealer).

Freon does 'escape' through rubber hoses, rate depends upon the quality of the hose. I have never owned a vehicle with A/C for long enough to know how long that might be. 134 is worse than the old R12 (smaller molecules I have read).

Have no idea how to check the compressor efficiency. Have you considered performing the A/C temp output test, as described in one of my other post? but of course, you have a FSM, and can read the test from there.

That is really the only objective way to determine the A/C system output efficiency, and whether or not your A/C output is really 'weak'.

Certainly, I am interested in your diagnosis, of your own vehicle, and resolution.

737 Jock

It was just a quick comment. You are correct about the relays, of course.

I'll put the RDX up when I am done with the #$@& GTI.

RangeRider49er

Wow, I wish I had found this post sooner! I just put my car in the shop for this very problem! They charged me $241 for recharging the freon and troubleshooting the problem to replace the compressor clutch relay! The battery was drained dead overnight and the freon had vented to to high pressure in the system since the condenser fan wasn't running due to the relay being shorted! Great thread though! The NAPA part # is AR614 and costs $22. Simple fix anyone can do if they know where to locate the faulty part. Diagnostic codes of little use on this kind of problem! I will try to post a picture of the part location in the engine compartment later on this thread.
BTW, our car exhibited several of these symptoms noted by DC Models such as hissing heard while driving due to freon venting due to system over-pressure, dead battery, condenser fan not operating when a/c was on. The compressor was running continuously even though the a/c was not selected 'on' by driver! This is the relay failed closed scenario noted above. I also will start replacing these relays and keep a supply of several on hand.

RangeRider49er

I took some pictures of my car showing some of the things DC Models thoroughly explained in his description which is expertly done. Just a little extra icing on the cake to embellish a bit!

Compressor visible to the left of the radiator hose. This is where you will see fumes rising and splatter of freon.

Compressor is just below the alternator!

Engine Room Control Unit Box next to brake reservoir.

Inside Control Unit Box

Lid of Control Unit has diagram of fuses and relays. You are looking for the one with the 'snowflake'.

Finger pointing at a/c clutch relay to replace. The black relay is the AR614 from NAPA. It is working so far!
Sorry the one picture is so big, I couldn't get it reduced for some reason!

My car has almost 150k miles on it so we got good life from that little relay!

RangeRider49er

BTW. I talked to a local Acura dealer today about the difference between the two relays and this is what he said. The dealer said that the original part number for the a/c compressor clutch relay was 39794-SDA-A04 (pre 2010) and was changed/upgraded by the now current relay part 39794-SDA-A03 and the newer models now use part 39794-SDA-A05. I hope this helps and the dealer was correct as I don't have a clue! Current parts diagrams only specify the 39794-SDA-A03 for the older models of the RDX!

jmsodpc

so here is a quick photo of my 2011 mdx....where is this fuse panel?
do i have to remove something to find it?

jmsodpc

ok..i found the panel...which relay is the a/c clutch relay?

dcmodels

Well, you have an MDX, so why not post in that forum? Anyway, there should be a picture under the lid of your MDX relay/ fuse box.

Now, look at post #6 above. Look at picture #5 in that post, which shows the bottom of the lid on the relay box.

The picture shows, from left to right and top to bottom, that there are three (3) columns and four (4) rows. The bottom row has only 2 columns. The leftmost column, of row four (4), contains the A/C compressor relay. The emblem looks like a snowflake, as indicated in post #6.

So, the only thing I can say is you are looking for the position of the *snowflake* on the lid of your MDX relay box.

Otherwise, check with the dealer, or post in the MDX forum.

Master Apex

Wish I read this post before taking my MDX to the dealer.

Took my 2008 MDX to dealer for :
- AC not working, compressor making crackling noise and discharging freon
- Battery Drain

Dealer said the AC Clutch relay drains the battery and could have damage the compressor but we agree to just fix the AC Relay and refill freon.
The cost is $1100 (would have been $1900 if we want to replace AC compressor too).
Car will be ready tomorrow.

Now, I feel $1100 is too much.

dcmodels

$100 to diagnose and replace the relay, another $150 to refill freon - so what else was done to your car? Replacing the AC compressor should not cost more than $1100 - are you sure nothing else was done? its best to check and ask before having the work done (and paying). Just wondering if dealer did something else?

Master Apex

Actually $1100 is for:
- AC relays - 4 of them
- AC Clutch set - 1, about $300 part
- Labor about $600

That's why he recommend that I replaced the AC compressor too ($800 part) since the labor is already included.

Wish I read up on this forum and learn to DIY , would have saved me $$.

SA said the AC clutch set was replaced because it looked scorched. It may still be functional but he thinks it will fail soon. If I had known about it, I would probably just replace the relay and leave AC clutch as is to avoid the $600 labor.

dcmodels

Are you unaware that the warranty for the AC clutch was extended? you will have to search to find the thread, in DIY or main (?), to determine if you qualify. You, like most new posters, did not list your year and miles, or any other info about your car - so I cannot say for certain if you qualify. Post in that thread if you have questions, but that would save you $900

OK, here is the extended clutch warranty link:
https://acurazine.com/forums/showthread.php?t=876148

dcmodels

BIG OOPS on my part - you did state that you have a 2008 MDX, not an RDX - and I get confused when people post another model car in an RDX thread.

In any case, the warranty for the RDX A/C compressor clutch was extended to 7 years/ 100K miles. And since the original TSB for the relay problem was specifically for the MDX, I would suggest that you speak to your dealer, and call Acura corporate, and ask for some *relief* in money for your clutch replacement (good will repair). It can't hurt. Certainly the TSB indicates that Acura is aware there is a problem.

I would also suggest that to decrease wear on your new AC clutch, that you specifically turn OFF the AC compressor when you don't want cold air, instead of allowing the HVAC system to always run in AUTO mode. On my 2009 RDX, when the HVAC system is in AUTO mode, the AC compressor (and clutch) cycles constantly whenever the vehicle engine is running, regardless of whether the temp is 10 degrees or 110 degrees. That constant ON/ OFF cycling wears the clutch face.

RamMan4x4

Thanks for putting this thread together! The AC in my '07 RDX quit working at some point over the winter. I checked the compressor and noticed the clutch was not engaging when the AC was turned on.

I tested the field coil per the instructions in the "DIY Field Coil Replacement" link you posted. Oddly enough, I measured a similar resistance as Bit359, 4.4ohms which is out of spec, but close enough that I didn't think it was a problem. I swapped the AC clutch relay with the AC condensor fan relay and it fixed the problem...other than the fact that the passenger side radiator fan (condensor fan) doesn't work now.

My question is, will it be ok to run the AC without the condensor fan part time until I can get a replacement part? I only ask because my wife and 1 year old child use the car to commute to work and they have been sweating on the ride home the past two days. I would assume that as long as they are moving at a decent speed, the air flow across the radiator should be OK with only one fan running. Thoughts?

dcmodels

I would not - its only a trip to any auto parts store (or Honda dealer) for a relay. Use your lunch hour. Call around first to save time. You can get the OEM part later. And the part from a Honda dealer is the same as the Acura part. I gave the part number in the OP.

The temp gauge is not accurate - its *buffered* and will always read the same +/-30 degrees, which means by the time it reads hot, its too late.

And from where I live, I cannot imagine sweating this time of year. Yesterday it snowed.

dcmodels

I was not going to try explaining this, but the problem is not so much that the engine might overheat, but that there may be a problem w/ the AC compressor, if the AC fan does not run when the compressor is running. I think that the problem is that the freon pressure may build up too high (from lack of adequate cooling), and vent from the AC compressor. Perhaps there is an AC tech who can explain further.

Tomtwtwtw

The compressor should automatically turn off if pressure gets too high. I've had a fan die on me on a much older car, and the compressor just cycled on and off at idle, yet ran fine while moving at speed. I have to think the RDX a/c would do the same. Of course, power-cycling the compressor like that is a great way to burn it out ahead of schedule.

RamMan4x4

Thanks for the response guys! I wasn't able to get a replacement part last night, but I did pick one up from O'Reillys this morning on my way into work. Just for reference, their part number is 25-0395 (Import Direct brand) and it actually came with a genuine Honda part 39794-SDA-A03 inside the box. Note that this is the original part number for the relay, not the upgraded part listed in the OP.

Unfortunately, my wife drives the RDX and we drive in opposite directions in the morning so I won't be able to install the relay until tonight. I told her to only use it if she absolutely needs it and not to use it at speeds below 35mph. So long as she is moving, the air flow across the condensor should be OK without the fan. As for temperature, it is supposed to get up to 85degF here today...much higher than that inside a black RDX parked in the sun all day.

My plan is to install the relay tonight in the AC condensor fan slot and order the upgraded relay for the compressor clutch. When it comes in, I'll swap it out and keep the old relay (that was originally in the AC condensor fan slot) as a backup.

Thanks again for your help and for taking the time to create the thread!

dcmodels

Sure, but what can *actually* happen, as described in the TSB referenced in the OP (original post) above, is that the freon vents from the compressor over-pressure relief valve. While that *may* not happen, it *can* happen. It just depends ...

TO RamMan4x4
Glad that you got a new relay - this afternoon here it was 40 and overcast w/ slight snow flurries

RamMan4x4

We had those temperatures last weekend and will probably be back to them next week...but, I'm enjoying the weather this week while it lasts.

UPDATE: My wife said the AC worked fine yesterday, she just turned it off whenever they stopped moving. I installed the new relay and everything seems to be working properly. I should probably check the pressure in the system just to make sure it will perform properly when summer gets here...

SinCity

The puller looks like one you use to pull EPROMS out.

dbl2010

I had exact same symptoms on my 2007 RDX and the car was more than 7 years old. So I bought 39794-SDA-A05 from local ACURA dealer (was $33). I used needle-nose pliers to remove the old relay. It was very easy to pull that out. Almost no force. And plugged in the new one. And A/C started to work again. A 5 minutes fix. Thanks for the well written info.

Lanesky_OH8RDX

I just went on a road trip and on the way to the destination after an hour of driving we slowed down to take a break so I turned the A/C off and opened the window. Once we got moving again and on the highway I closed the windows and turned the A/C on and the compressor engaged but it wasn't blowing any cold air. Could this relay be the problem or maybe is it something like the condenser? Like I said the compressor engages since I can A) hear it. And B) feel the car gets sluggish due to the parasitic drag from the compressor. So I think the compressor can be ruled out as an issue and I can imagine the bill to take it to Acura to fix. Any help super appreciated.

Lanesky_OH8RDX

I re-posted this in the Problems&fixes section. Figured that's the more appropriate area for my problem. Mods please delete these past two comments thanks.

jnor10

Thanks for this post! My last road trip in our 2007 RDX, it was discovered that the A/C was intermittent, it just seemed to work when it pleased. I also discovered I was out of the warranty period, so considering an expensive A/C repair instead I simply replaced the A/C relay as a gamble and it worked!

My wife is on a road trip in 98 degree heat and reports the A/C is working just fine!

hhrdx08

Thanks to dcmodels, great thread.

Could anyone show me the locations of the relays for items 3, 4, 5 & 7 listed below? TIA

3) A/C condenser Fan
4) Electronic Throttle Control System (ETCS) control
5) Radiator Fan
6) A/C compressor clutch
7) PGM-FI (programmed fuel injection) sub-relay

hhrdx08

Ah, silly me. They are in the same fuse box.

acurardx15

can someone tell me what relay 1, 2 , 10 , 11 and 9 is and also theres a little box below this fuse box saying vuccam fuse and theres 3 other relays i was wondering what that was also

wifesRDXtech

Subd

having issues with ac after owning 2007 Rex tech since new. Will try the relays first

wifesRDXtech

I called Acura and they said the part number ends in 03 asked him about the 05 part number and in his notes it says it supersed s an 04 part number after hanging up I found 03 is superseded by 04 and that's superseded by 05 not in his notes

Will get the 05 as I think dealer is still selling 03 ? I will go there tomorrow And report back after.

This below is copied pasted from OP:

The original part number is 39794-SDA-A03 manufactured by OMRON in the USA

The upgraded replacement part number is 39794-SDA-A05 manufactured by MITSUBA in Vietnam. As best I can tell, this upgraded relay has been used across all of the Honda/ Acura model lines for the past 3 model years, so that it is unlikely that the new part number will cause any problems itself.

bchizzle

Just wanted to contribute! I felt that my a/c was working over time at lights and while parked.

I changed out the relay (Amazon $17.95 - 39794-SDA-A05) last week and I can noticed a difference right away just starting up. I drove it through stop and go traffic and could tell that the relay was definitely working. While the a/c still causes a very slight kick, it's definitely 100 times better.

Thanks for this thread! Keep up the great work!

SinCity

For the past three years, every once in a while the AC would stop working during hot weather. I would turn it off and drive around and turn it back on and it would work. I'm assuming the relay is going bad when the engine compartment gets hotter during the warmer months. I finally decided to replace it with one from O'Reilys.

ben_shafer

Hey guys I have a quick question. Currently I have intermittent issues with BOTH my A/C and my Heat on my wife's 07' RDX . Does the AC Clutch relay have anything to do with the heating system? Just weird that the issue is happening to both AC and heat.

Tomtwtwtw

Yes, the compressor will also be used to generate heat if called upon.

SinCity

UPDATE: It was the compressor. It went out a week later in one of those 110+ days we had in Vegas. Mileage was just a bit over 117k mi.

flej100

Hi There,

I swapped out both relays and am having an the issue where the AC Compressor fan does not turn on. I think this causes overheating, and then the AC shuts down. Any ideas?

Thanks

Altair

Welcome!

Are both fans working by themselves?

Get a 3-4 foot long telephone wire with cut and exposed conductors.

With car off:
Disconnect each fan harness and use the cable to connect battery terminals to the plug from each fan. Do they spin when powered?

Same cable can be used to test the relay socket in the electrical box by removing the relay and cross connecting position 1 and 2.
Which relays did you check, there are 3 related, A.C. clutch, A.C. fan, Radiator Fan?

If fans and relay socket works, then the relay is still suspect.
If fans work and relay socket doesn't, then the wire from the relay to the fan is suspect.
If fan(s) does not work, then the respective fan is suspect.

Fix and repeat tests.

hope you find the culprit.

flej100

Thanks for the response!

I'll have to take some time to go through some of that testing. But, to answer your question, I checked both the A.C. clutch relay and the A.C. fan relay. The radiator fan seems to be working fine, so did not check that relay.

Does it make sense that the AC fan not running would result in intermittent cooling?

Also, would you mind elaborating on how to cross connect positions 1 and 2 of the relay?

Thanks again.