Automotive Air Conditioning Information Forum

The AC in my wife's Acura RDX has been acting a bit strange over the last year. If the ambient temperature is over 90degF the system will refuse to even run. At temperatures of around 90F and below it works and blows very cold air...as long as the car keeps moving it will continue to work, but if I get stuck in traffic the compressor will shut off and stays off. If I park the car and let it sit for a while (overnight usually) the AC will work again. I initially suspected the condenser coil fan, but it comes on at high speed anytime the AC is turned on...even if the compressor doesn't actually engage.

Some extra background...2 years ago, the AC stopped working and the compressor wouldn't spin. I diagnosed it to a failed clutch coil relay. Replaced the relay and it worked fine until the next year. When the AC stopped working again and the relay wasn't the problem I started looking around online. I found several posts talking about failed clutch coils and then found that the part was given an extended warranty from Acura but that ran out a couple years ago. I bought a new coil and installed it, but that didn't fix the problem. My fault for throwing parts at a problem instead of diagnosing them first. I gave up and took the car to a local mechanic...they evacuated the system and told me it was about 1lb low and refilled it to what they said was the correct volume...though when I asked the guy what it was filled to, his answer was vague so I don't know how much he actually put in. Obviously this didn't fix the problem or I wouldn't be creating a new post.

So, here's where the car sits today. If it is cool outside in the morning, the AC works and these are the pressures I am reading:
Low Side: 44psi
High Side: 110psi


After the system warms up:
Low Side: 32psi
High Side: 123psi


After everything gets too hot and the compressor stops:
High and Low Side: 140psi


The only thing I can think of is that it doesn't have enough refrigerant which allows the system to overheat too quickly/easily. Any ideas?

Might help to know the year of the vehicle.

What was the ambient temperature when you took those pictures? What speed was the cabin fan running at?

What is the clutch gap set at?

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What was the engine rpm when you took those pressures?

2007 Aura RDX

The first two pictures with the compressor running were taken in the morning with an ambient temperature of 75F. The last picture when the compressor isn't running was taken the night before after driving home at 90F.

Engine speed is at idle which is approximately 1000 rpm.

Cabin fan was at max speed.

I'll have to check the clutch gap. Like the novice to hvac that I am, I just reinstalled the same 2 or 3 shims on the clutch that came off.

I can try the wooden handle trick that I have seen recommended elsewhere on this forum, but I assumed the low side pressure was too high and that was why it wouldn't engage the compressor.

Just check the gap, and if it is more than 2 business cards (or one credit card) wide, adjust it.

RamMan4x4 wrote:2007 Aura RDX
The last picture when the compressor isn't running was taken the night before after driving home at 90F.

High and low sides will equalize when compressor is not running. That is totally normal.

bohica2xo wrote:Just check the gap, and if it is more than 2 business cards (or one credit card) wide, adjust it.

Seems like you are on the right track...I tried the wooden handle trick tonight after the compressor stopped working on the way home from work. There isn't much space but I was able to put some pressure on it with a wooden dowel rod and it started back up. I'll measure the gap this weekend...clutch is tucked in the lower engine compartment and is not easily accessible, especially with a hot engine.

From what I have read, you basically want the clutch gap as close as you can get it without dragging the pulley when the clutch is disengaged...but is there a target clearance? 0.020"?

.020 is about the maximum you want. It is hard to measure on a used clutch because the plate and pulley usually wear into each other in a matching groove pattern. Trying to measure that with a flat feeler gauge makes you think the gap is smaller than it actually is.

Bottom line just take some shims out and test drive.