Hello everyone. I really need someone to help me, as I've been going crazy trying to solve this problem. The a/c in my 2005 civic LX likes to run on its own at random times. With the a/c switched off, and the blower set on any setting, it intermittently turns on and off, sometimes staying on for long periods of time, and sometimes rapidly turning on and off. During this time, the a/c light remains off, regardless of whether or not the system is running. To be clear, the compressor clutch and the fan both run when this is occurring. Often it runs long enough to freeze over, resulting in no usable a/c.

I have replaced all associated relays, the PCM, the multiplex unit, and the hvac control panel, with no results. I am unable to find an apparent short to ground in the wiring that I can see.

Can someone PLEASE help me solve this stupid problem? ANY input is appreciated. If there is anything else in the system (pressure switch, temp sensor, etc) that is capable of turning on the compressor and fans, let me know. I really am sick of this.

 

Check the A/C system for leaks or restrictions and then have it recharged with refrigerant. Cycling on and off can be a result of low pressure.

 

Here is the diagram for reference

 

I actually already had it in a shop, where it was checked for that, along with other things. They were unable to find the problem. Even still, a system that has too low of pressure should not run non-stop when it is switched ON, but should not run at all when switched off, right?

I am about 99% certain it is an electrical issue. The way that it acts when it is turning on and off rapidly on some occasions is far too quick to be a pressure issue.

 

Any one have any suggestions?? Bump

 

Update: After replacing the multiplex AGAIN and the HVAC controls, the problem remained. So, I did what any normal person with no more ideas would do: Started poking wires and harnesses with a plastic stick. Well, what do you know!? When I poke the two wires coming into/out of the thermal protector on the compressor, the A/C and condenser fan (that are running with the button turned off) turns off. While holding the stick on these wires, I had my wife push the A/C button on and off a few times, and the A/C turned on and off with each press. See, the thermal protector is designed to open the circuit if the compressor gets too hot. That means it can only PREVENT the compressor from turning on, it cannot provide power on its own. So, what does this mean for my system? How is gently poking the wires in the thermal protector shutting the A/C and condenser fan off, but still allowing me to turn them on with the button push?

According to the diagram there is no way that the thermal protector can provide power to the compressor clutch, but it seems that not only is doing that, but it is also providing power to the condenser fan. I'm at a loss, yet again.

 

Ive has the same issue with me 02 ex since I bought it