A/C blowing warm air?

SPUDMELON

MEMBER
2007 HONDA CRV
2.4L
4 CYL
4WD
AUTOMATIC
150,000 MILES

Hello!

I have been chasing an A/C issue for a while now. The car would blow ice cold a/c and just randomly stop. After it did that for about a few months it finally quit and never came back. Took it to Firestone and all they did was put dye in it and told me to bring it back to check for leaks. After chatting with a few other CRV owners they said they had the same problem and I was the expansion valve. I replaced valve and the pressure was reading fine at 40 PSI. Now the compressor the pressure is currently reading 150PSI on the low side because the compressor is not engaging. I did some diagnosing today and found that the compressor is not locked up and spins manually okay. I am however not getting any voltage to the compressor plug. I traced back to the relay which is getting 14 volts, I checked all fuses, and they are good as well. No leaks in the system. So, my thoughts are the system is overcharged and being shut off by the pressure switch it also may possibly air in the system. What would be my next diagnoses step?

If you need any more info let me know I can test more things if needed.

10 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi,

Are you seeing 150 PSI on the low-pressure side of the system? What is the high-side reading? Also, what was the outside temperature when you checked the pressure? If the static pressure is 150, the outside temperature should have been approximately 110 degrees F.

Next, I realized you checked the relay and fuse. I attached a pic below showing the fuses related to actuating the compressor clutch. At the relay, there are 4 pins. If you remove the relay, there will be numbers identifying each pin.

On the relay primary side will be pins 85 and 86. On the relay secondary will be 30 and 87.

Here is how this works. When the A/C is requested on, the powertrain control module provides a ground path to the relay primary side (either pin 85 or 86. Each manufacturer can be different). When that ground is provided, then power from fuse 36 (under the dash fuse box) runs through the relay creating an electromagnet. The magnetic field draws the switch closed on the secondary side and power is then able to reach the compressor clutch.

Here is a link that explains it in more detail:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

What we need to do is check if the fuses are good and have power first. Then, remove the relay and with a test lamp, check the connectors. One of the pins will have constant power regardless of the ignition key position. (Secondary pin 30 or 87) If that is present, we need to check the primary side for power and a ground signal from the PCM. First, determine if it is pin 85 or 86 that has power with the key on. Once that is determined, check the other primary pin (55 or 56) for a ground path.

To check for a ground path, connect the alligator clip of a test lamp to the battery positive and probe the light to the ground pin. If a ground is present, the light will turn on. Note: the key has to be on and A/C requested.

I know that sounds like a lot, but it isn't too difficult. If you have questions, let me know.

Take care,

Joe

See pic below.

Image (Click to make bigger)