ggoodwin

Hi All,

I have a 2009 civic lx-s and have been having some problems with the AC system that I could use some help diagnosing. The AC compressor clutch was not engaging when I would turn my AC on in the cabin, so I replaced the compressor clutch relay and that fixed the problem - all was working just fine for a couple of months.

Then I started to notice that the compressor and condenser fans would cycle on at times when the AC was turned off in the cabin, and sometimes even when the climate control system was turned off completely. The times it kicks on seem pretty random - sometimes they run for ten minutes or so and sometimes they cycle on and off in seconds. In this cold weather (I'm in the Northeast), there is ice buildup on the low pressure lines and on the compressor itself if it stays on for more than a couple of minutes.

I tried replacing the relay again as the obvious fix (using an OEM relay), but the problem is still occurring. As a band-aid fix I've pulled the relay so that the compressor doesn't run and build up ice on the lines during this cold weather.

Has anyone encountered this before? I assume this is an electrical problem, but why the compressor clutch and condenser fans would cycle even with the climate control system turned off is a mystery to me.

Thanks for any advice!

Jp7

iTrader: (2)

I have seen cars that turn on the AC compressor to purposely generate load and make the engine warm up faster when it is cold. This is part of an emissions strategy to get the engine to running temperature sooner. Assuming this is what is happening it should not do it when the car is fully warmed up though.

Check and see if your PCM is providing a ground to the control side of the relay- because it if it, the relay is just doing as it is told. You would then need to understand why your PCM is commanding the relay on. You could have an issue with the PCM. See if the AC compressor relay turns off when you go wide open throttle. Most PCMs will disable the AC compressor when you go WOT because you want full power then. You could have some sort of short to ground in the control wire that allows the PCM to give it a ground. If this was the case- you could take a test light connected to battery positive and see this with the car off by connecting to the control wire.

ggoodwin

Thanks for the reply. I've been keeping track of when the compressor/fans kick on since you posted that, and it seems like it's always happening during startup and before the engine is warm.

I haven't noticed them kicking on (without me telling them to) after the engine has warmed up a bit. The loading of the engine to get up to its minimum emission profile makes sense, since these were marketed as "ultra low emission vehicles".

Thanks again.

ezone

What brand is it?

Unplug the hvac control panel and see if that shuts off the AC system