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I have a 2003 civic lx with a strange A/C issue.
It works beautifully most of the time. However, once in a while it wont work. I went through all of the basic checks, everything looks good. I popped the hood and let the a/c run for a while. The condenser fans come on and are surging. This is accompanied by a rapid clicking from the underhood fuse and relay center. I tried swapping around relays but this didnt help. I dont have access to a wiring diagram which could allow me to dig a bit deeper. Someone mentioned that a compressor temp sensor could cause this headache. Any help would be.great!

 
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Bump Anyone???

 
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Define "not working". Does it stop blowing cold air? Does it blow warm air instead? Does the blower motor keep running? Have you checked the low side pressure? The fans and compressor should all kick on at the same time. That is normal.

 
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It stops blowing cold air, warm air only. The surging I am speaking of is not the typical cycling of the ac compressor or the condenser fans. The relay actually chatters very fast. The fans range from normal speed to off just as fast. This will happen 2 or 3 times and then the pcm locks out further attempts until the key is cycled. I got a basic wiring diagram from alldata, im wondering if the thermal protection switch is causing this headache.

 
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What's the low side pressure?

 
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35 psi @ 2000 rpm.
Cold as could be right up until the chattering of the relays begins

 
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Can you identify which relay is clicking/chattering?
I'd probably start there and then identify which of the 4(?) circuits at that relay is causing it to chatter.
Then follow that one wire in a diagram and diagnose why.
Sorry, no silver bullet yet.

On an 03 the thermal protector would interrupt the AC request line between the HVAC control panel and the MICU. That means the radiator fans would not run with the AC switch on either--- until hot coolant temp turned them on.

(01 was the only 7th gen that the thermal protector shuts down the compressor clutch by itself...fans would keep running on those.)

 
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What you are describing is pretty much a mirror to what my car is doing. Is the thermal protector replaceable on the compressor?
I traced out the wires on the digram. It seems like there is a logic circuit that would shut off the compressor relay and the condensor fan relays if the thermal protector were faulty.
I bolded the statement in your response. My car is doing this. It will try to run the A/C about 3 times before it completely locks out an A/C request until the ignition key is cycled.

 
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Yes it is replacable. It'll cost you about $50-80 depending on where you shop for it.

 
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What you bolded only tells me that the AC isn't running for some reason other than the compressor.


I would want to look on a scanner datalist to see if the PCM receives an AC request, and see if the PCM is carrying out that request.
The HVAC controller sends a request signal to the MICU. (This can be interrupted by the pressure switch or the thermal protector switch, they are wired in series with the request line.) (The "request" is simply grounding the signal wire.)

The MICU then requests the PCM to turn the compressor on.
The PCM can override the AC system request for many reasons. Excessive coolant temperature is a common reason.



If you think the thermal protector is the cause, you could simply jumper those 2 wires and find out.
Actually, if you measure to see if the blue/white wire at the thermal protector connector is grounded, that would tell me a little info. Or just ground that and see if the comp will kick in.

Get a wiring diagram and you should see how this works..

 
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Subie guy here, poking around these forums. I have seen problems like this on my beloved Imprezas.

Ideal gas law basically states that if a gas gets hot, it expands. Sometimes, if your system is at the cusp of being overfilled, and the outside temp gets high enough, it'll kick the pressure sensors in the system to prevent it from damaging anything.

Your pressure might be on the verge, and you might be tripping the protection. Try going down the highway at highway speeds and get some good, fast moving cool air through your condenser and see if your AC works right after having this issue, and if it does, I'd bet letting some of the pressure out would solve your issue.

 
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After inspecting the system, which included an evac to see how much refrigerant was in the system, which by the way was smack in between min and max level, I found the thermal switch to be pretty much crushed from the surrounding corroded aluminum. I replaced it this morning. So far the system functions flawlessly. No more rapid chatter from the relays and no sign of intermittent fan actuation.