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I need help troubleshooting an air conditioning problem. I have worked on cars quite a bit. But, I don't have a lot of experience with troubleshooting air conditioning issues. When I first start the car, the air conditioning works just fine at idle. After driving the car, the low side port pressure rises to over 100psi, and then it blows only warm air. After driving, the pressure stays high, and it will only blow cold air again after the car sits for a while. Any help would be appreciated.

 
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Need to know

year/model/trim level/country
type of ac control panel
mileage on car

need to know the status of the compressor clutch when pressures are not correct and air is not cold

 
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2008 civic ex 115,000 usa. Conttol panel is just regular *****. The compressor clutch is disengaged when the pressure gets high.

 
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Ok.
Radiator fans are supposed to run at the same time the compressor clutch is engaged...(they all cycle together on that car)
so when the clutch quits engaging, are both fans still running?

 
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I will check tomorrow.

 
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Ok.....if the fans continue to run when the compressor quits, that narrows it down to something among coil/clutch/relay/wiring

but if the fans shut off too then it's probably something else like maybe the thermal cutout switch

 
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I will look at it first thing tomorrow. It is actually an lx, not an ex. Not sure if that makes a difference.

 
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I was not able to check the fans or clutch when the car was cold. But, after a 30 min drive with the AC turned off, I let it idle for a minute, then checked the fans clutch, and pressure. The pressure was over 100 psi, without the AC running at all today. Both fans were on, regardless of the AC being turned on or off. The compressor clutch did not engage.

 
Rep Power: 518

Ok...based on what you've described (and the mileage) I'm gonna guess the main issue at the moment is the gap between the plate and pulley is too wide (due to normal wear)....
I could explain why this is my theory if you really want to hear it.....


Checks to confirm:
Air gap between clutch plate and pulley LOOKS like it's at least full millimeter or more wide (actual gap spec is about 0.5mm)

While it's engaged and working, sometimes you may notice an obvious wobble in the outer ring of the clutch plate as it spins--- because it's not being pulled completely 100% flat against the spinning pulley (just something I've noticed over the years on these, but not all do it)

after it quits working, with system still turned on and engine running, you could use a long tool to physically push the outer clutch plate up against the pulley, it should then engage and will usually work again, but just until the clutch is turned off (via normal system cycling)....that would confirm the electrical parts are still working (relay/wiring/field coil)



If all this guesswork is accurate, the cheapest possible approach (FREE) would be to remove the outer clutch plate and remove an adjustment shim (assuming there is at least one or more in there)---to make the air gap narrower, this should last until wear makes the gap too wide again


Relay or field coil failures are also possible (and somewhat common issues), but if you can push on the clutch plate and make it engage then the relay and field coil are still working at that moment.

 
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I will check this tomorrow.

 
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I pushed the clutch in with a broom handle, and it stayed engaged. I will take the clutch apart as soon as I have time. Thank you for your help with this.