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Discussion Starter #1
I’m having this terrible time with the A/C in my 2009 MDX. Basically the front air vents don’t produce any cold air.

The driver’s side is cool until I start driving, then it get quite warm. The passenger’s side stays lukewarm (usually cooler than the driver’s side). The rear gets ice cold every time.

I’ve scoured pretty much every forum post to fix this issue and nothing has worked yet. There’s a brand new compressor (just installed last week) that starts every time and I can see condensation under the car (plus the rear A/C works perfectly). I’ve also tried greasing up the air mixer on the driver’s side but that didn’t do anything.

The car has no trouble changing to heat on all vents and there are never any strange noises inside the car.

I’m stumped. Do you guys have any suggestions?

Thanks in advance, Kyle.
 

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Had same issue on 2009 and it was the A/C relay under hood. There was a problem with them so they introduced a new relay and part# to replace it. If it was not changed out all ready you probably should change it out! There is also a 7.5 amp fuse in the same fuse box which you might want to change out as well. You can actually switch the large relay with the other similar one in the same fuse box and see if it does not fix the issue. This is the simplest starting point!
 

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Remote diagnosis is difficult but the symptoms that you are seeing, I have before. It was low on Freon in my case.
 

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Discussion Starter #5
When I got the compressor replaced they flushed the freon so it should be at the correct level. Thanks for the help so far.
 

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I’m having this terrible time with the A/C in my 2009 MDX. Basically the front air vents don’t produce any cold air.
If you are sure the loop was filled again correctly after the compressor replacement, it's likely the A/C relay.

I just swapped like ever fuse in that box and nothing solved my problem.
Relay is not a fuse.
 

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Relay is not a fuse.
. The relay is a 30amp rectangular not the mini ato fuses below them.These relays as already stated heat up and become intermittent which makes them difficult to troubleshoot! On"rare occasions" you can shake them and hear rattling but in most cases this is not the case and so individuals assume they are fine which is incorrect. The Relay #39794-SDA-A05 is the one you want and i would recommend you have at least one spare as these relays are used elsewhere in the vehicle also.

As mentioned replace it as a test with the other relay in that same box and try your a/c again.
 

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Discussion Starter #9
Thanks for the suggestions! I called my local Acura dealer and they have that relay in stock. I will go pick it up tomorrow morning... I’ll keep you guys up to date!
 

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Discussion Starter #10
Well I replaced the relay and the A/C still doesn’t work. Do you guys have anything else I can try?
 

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If you take it to a "general automotive" shop, they can evacuate, add dye, and refill the Freon, but if that doesn't fix it they will recommend a new compressor and maybe another new part or two.
If you take it to an "import automotive" shop who says they work on a lot of Hondas/Acuras they can evacuate, add dye, refill the Freon, shim the clutch disks, and work on individual parts of the system, without selling you a new compressor.
 

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Discussion Starter #12
I believe the compressor is working though because there is cold air coming out of the rear vents. Plus I can hear it turn on.
 

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I'd check and see if your heater valve cable is stuck in the open position. That would allow hot coolant into the front A/C system and warm the air. Make sense since the issue isn't occurring when the car is first started, but the a/c gets warmer as you drive. It also could be low on refrigerant, hook up some gauges and see what the pressures are.
 

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Discussion Starter #14
I'd check and see if your heater valve cable is stuck in the open position. That would allow hot coolant into the front A/C system and warm the air. Make sense since the issue isn't occurring when the car is first started, but the a/c gets warmer as you drive. It also could be low on refrigerant, hook up some gauges and see what the pressures are.
Where is the heater valve cable? I cannot find it for the life of me.
 

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Who actually replaced the a/c compressor? It sounds like they messed up so why don't you take it back and have them correct the issue?
 

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Discussion Starter #16
Who actually replaced the a/c compressor? It sounds like they messed up so why don't you take it back and have them correct the issue?
This is a good point and I already have an appointment with them this weekend so they can take a look at the issue again. I was just trying to see if I could fix it myself in order to avoid that hassle.
 

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I’ve had similar issues with my Odyssey and TL. On the odyssey it was the aforementioned relay.

On the TL however the blend door, which is controlled by the auto temp system, was faulty. It’s a combination or electronic and mechanical parts. For me the feared mechanism which moves the blend door was broken internally and needed a replacement. I would look in that area next.

Also I believe there is a diagnostic that can be run from the auto temp panel which may display a useful code and/or allow a system reset.
 

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I have to strongly concur on the blend or mixer door/motor. I’ve had similar issues on both a TL and MDX. Google blend door actuator and look on Amazon - lots of articles and you can often clean and fix yourself (I did). If you hear clicking, it may be the actuator as opposed to the door.
 

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Where is the heater valve cable? I cannot find it for the life of me.
If you open the hood and look at the firewall dead center of the engine you'll see the wire connect to a little box:
 

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Well I replaced the relay and the A/C still doesn’t work. Do you guys have anything else I can try?
I had the same issue with my 2011 and it ended up being the expansion valve. There was a great post From Kevinviau from 9/15/15 regarding similar issues. I actually printed it when I took it to my local Acura dealer (Roseville Acura) and they tested the pressures and found the front expansion valve was bad. Because they had to take out the evaporator to change the expansion valve, I went ahead and had that replaced too. It’s been perfect ever since. Have them check the pressures and see if it’s the expansion valve. Good luck.
 
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