I have a Honda Civic 2003. A few weeks ago, the air conditioner starts blowing out warm air. The mechanic told me that PCM is not working, and I need to replace the PCM. He did show me that the compressor is working, and it blows out cold air when he jumped the relay to start the compressor.

I don't know anything about car, so want to ask your opinions.

- Is it possible that a bad PCM can cause this problem?
- If I replace the PCM, what can I do with the old PCM (since everything else is still working -- it still drives fine; only AC is not working.

Thank you,
-JB

 

Yes this is possible though it is rare. Basically the A/C button sends a command to the PCM, which will boost the idle speed slightly to prevent stalling, then the PCM turns on the relay to engage the compressor. If your mechanic has thoroughly checked everything else, a new PCM will solve the problem.

 

Thank you very much. Couple follow-up questions:

- Do you know what might have caused this?
- The mechanic said PCM would cost $550, and it would have to reprogram it, which would cost $250, and he would charge me $300 for labor. Does this sound reasonable?
- What can I do with the old PCM, since the rest of the system is still working?

Thank you.
-JB

 

[:-]

try ebay. there's a possibility they might or might not have it. But if they do you'll get it very cheap!

 

Sell it on ebay.

 

This sounds sort of like the problem I'm having. I turn on the air, it blows nice and cold. Then sometimes like 20 minutes later the air goes lukewarm, then after awhile goes back to cold. I wonder if my 95 has the same problem. Hmm.

Do you know where the relay is, and what he jumped to make it turn on? I'd like to run a wire from it so I can watch the status and see if it goes off when my air goes warm.

 

The first thing to check on a problem like that is to see if the compressor is still engaged when it is blowing warm. The plate on the pulley end of the compressor spins when it is engaged and sits still when not. If it is blowing warm with the compressor engaged, there is a different problem. Also note if the condenser fan is running when it is blowing warm.

If it is not engaged, you can measure the voltage on the wire going to the compressor (it is a single wire) to see if the system is trying to engage it. The relay is next to the left headlight near the compressor.