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Guest Spyderbyte

Air Conditioning Compressor Doesn't Seem To Be Working

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Guest Spyderbyte

Hi everyone-

 

Summary- 2006 Corolla, can manually engage ac compressor, but it still doesn't seem to work

 

Details-

The air conditioning has been terrible for at least the last couple years. I picked up a R134a recharge kit with pressure gauge, started the engine, turned the AC on full blast, hooked up the pressure gauge to the low side port and read 70 psi... Investigated some more and discovered the compressor clutch wasn't engaging. It seemed to be getting voltage, so I lightly tapped the clutch, the compressor engaged, low side pressure dropped to ~20 psi, looked like a simple fix. I turned off the engine, prepped the recharge kit, turned everything back on, nudged the clutch, compressor engaged, low side pressure still at 70.... Dang. Tried everything again, this time the pressure dropped to ~20 psi again, I added 6-8 ounces of R134a (the pressure climbed to ~40 psi and stayed there for most of the addition), and for a few glorious minutes the vents were blowing ice cold air and all seemed to be working beautifully. I let it run for a few more minutes, then turned it off and let everything sit for a few minutes. Turned it all back on to see if it really was fixed and..... nope.

 

Here's where things stand at the moment- I can tap the clutch and get the compressor to engage (I've heard this can be due to too much gap, but I'll tackle that later) but it doesn't seem to do anything. The low side pressure stays high (it was up around a hundred psi after the additional R134a when the engine was hot and ambient temps were mid eighties) and the vents blow warm air. Turning the AC off disengages the compressor, and I can only coax the clutch into engaging when it's "supposed to" (only when the AC is set to on).

 

I've been hoping all along that this was just due to low refrigerant levels, and for a while it looked like it was. However since the low side pressure doesn't change when the compressor is spinning, I can't help but think the compressor itself is bad. What's throwing me off is the two times it seemed to work perfectly (low side pressure dropped, and cold air at least the second time (I didn't check the vents the first time))

 

Any thoughts?

 

Thanks!

 

Spyderbyte

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trap

Sounds like an intermittent electrical connection to the magnetic clutch on the compressor. Is there anything else out of the ordinary? Frost on any of the piping under the hood, A/C LED light is ON when A/C is engaged (i.e., not blinking)? Any of the soft hoses on the A/C system appear to be wet or distorted? Double checked that the serpentine belt is in good shape?

 

The compressor is not engage if the pressure is too low or too high. But your "tapping" experiment seems to point to an electrical issue (assuming you are tapping the clutch). If you are actually tapping the compressor body (smacking it with a hammer), could be excessive amount of moisture in the system or lubrication contamination - could be locking the compressor up internally. The times where it actually seems to work, would point to this second scenario.

 

Looks like you have a bit of a pickle here. If you haven't lost any refrigerant - this would be likely a compressor issue. But since nothing is "inexpensive" on the typical A/C system, don't want to just replace parts to diagnose this. Might be worth the diagnostic charge to have a dealership or HVAC specialist check it out. If anything, they can pull the old refrigerant out, "dry" the system and recharge. That way, you can rule out contaminated refrigerant as a potential culprit.

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Guest Spyderbyte

Sounds like an intermittent electrical connection to the magnetic clutch on the compressor. Is there anything else out of the ordinary? Frost on any of the piping under the hood, A/C LED light is ON when A/C is engaged (i.e., not blinking)? Any of the soft hoses on the A/C system appear to be wet or distorted? Double checked that the serpentine belt is in good shape?

 

I haven't noticed anything else out of the ordinary. I haven't seen any frost, the A/C light stays on, there's nothing of note about the soft hoses, and the serpentine belt appears to be fine.

 

The compressor is not engage if the pressure is too low or too high. But your "tapping" experiment seems to point to an electrical issue (assuming you are tapping the clutch). If you are actually tapping the compressor body (smacking it with a hammer), could be excessive amount of moisture in the system or lubrication contamination - could be locking the compressor up internally. The times where it actually seems to work, would point to this second scenario.

 

I am indeed tapping the clutch- just giving it a slight nudge toward engaging. I checked the two wire plug to the compressor and was getting voltage when the A/C was on (I think it was around 13 volts while the car was running, but I don't remember the exact number). What's the purpose of the single wire plug? (looks like it also attaches to the alternator)

 

Are you saying that it's possible for the clutch to be engaged and spinning yet the compressor is locked up?

 

Looks like you have a bit of a pickle here. If you haven't lost any refrigerant - this would be likely a compressor issue. But since nothing is "inexpensive" on the typical A/C system, don't want to just replace parts to diagnose this. Might be worth the diagnostic charge to have a dealership or HVAC specialist check it out. If anything, they can pull the old refrigerant out, "dry" the system and recharge. That way, you can rule out contaminated refrigerant as a potential culprit.

 

It's hard to tell if I've lost any refrigerant, I currently only have a gauge to measure the low side pressure. Would measuring static high side pressure help at all? I may have to cave to a diagnostic, but is there anything else I could/should check on my own first?

 

Thanks again!

 

Spyderbyte

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Sometimes the compressor can be locked and the belt will just slip around it. But in your case, sounds like it is just related to the clutch - compressor sounds like it is still OK.

 

Technically, you should be checking both the high and low sides to get an accurate picture of what is happening. Unfortunately, gauges are only good as their calibration - unless you can rent a shop grade set of dual gauges, I'd take the system in to a pro (that way you get a paper trail and usually a guarantee).

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I also have a 2005 where the clutch does not turn at all. I also have wonder what that single wire on the compressor is for. I checked it with the volt meter and it measured 14v(red lead on wire black lead on chassy) but the two wire harness measures 0v between the two.

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