Hey all- new guy here. Bringing home a 2000 Civic EX coupe tomorrow morning. 95k miles, runs great, very clean inside and out. Only problem is that AC doesn't blow cold. AC light comes on when dash button is pushed, but I can't hear AC clutch clicking to engage. I put a pressure gauge on the low pressure side and looks like there is plenty of pressure, so I am suspecting just an electrical problem. Checked the 7.5 amp AC fuse under the dash and the fuses under the hood; they all seem OK. Condenser fan runs and engine idles higher when the AC button is lit up on the dash. I tried to troubleshoot the relays under the hood by taking the known good relay (condenser fan, since I could see the condenser fan running) and placing it in the place of the MG clutch relay. Still no "clicking" to indicate AC clutch working. When I get it home tomorrow (where I have tools) I plan to put a test light on the wires coming to the AC compressor as a starting point. Problem is I don't know which wires are supposed to have power coming to them. Anyone have any other ideas?

 

What pressure did you measure on the low side? If you BRIEFLY jump the A/C pressure switch, does the clutch engage?

There's only one wire that runs to the compressor clutch - red. If it has voltage, check the clutch clearance:

 

Thx for the quick response! I picked the car up this morning and I rechecked the low pressure side of the AC system (with the car running and AC on this time!, I stupidly checked it with the engine off yesterday). Pressure was too high (around 70). I assume that the previous owner may have tried to recharge it himself and overpressurized the system. So I just dropped it off at the AC repair shop today; will see what their diagnosis is... I just decided I would rather spend my time doing other things today. Thx again.

 

What was the outside temp when you made the pressure reading? Depending on the ambient temp, this reading could mean the refrigerant pressure is fine or low, but it's unlikely to be too high. This is because, if the compressor clutch does not engage, then the pressure reading means the same with or without the A/C running.

 

ambient temp was about 65-70. shop just called. said that compressor clutch plate was missing. they think someone previous took it off and therefore likely compressor is bad. can the clutch plate bolts loosen and it just falls off? if so, just finding clutch plate and bolting it on seems a good first trial step. they say system is full with good pressure. but they want 1200 to replace the whole system (recommended) or 500 to replace just compressor with no guarantee that will fix it all. they are worried about possible expansion valvembeing plugged and want big money to replace it. i am tempted to try to find a clutch plate first...

 

^That's what I'd do. Post pictures of the compressor. You should also measure the resistance of the coil to see whether it is good. Is the red compressor wire currently connected? Does it get battery voltage?

You can buy the OEM compressor clutch kit for ~$120. Not sure what aftermarket would go for. The job can be done without disconnecting any refrigerant lines, if you have the patience to work in a tight space.

 

Just got home from camping and checked the red wire coming to the compressor; doesn't look like it is getting 12V power. I took a picture of the compressor and will post them up later when I get a chance. With the car "on" but engine not running (key fully on) and the AC turned on, the dash AC light is on and the condenser fan is running, but I can't detect any power coming in the red wire to the compressor.

 

You need to test for voltage on the red wire with the engine running.

 

Thx, I will go do that in a little bit. To measure resistance across the clutch coil, the engine can be off, right?

 

Yes

 

Here is the best photo I could get of the AC clutch. Sorry, space is pretty tight. You can see the 2 coil wires coming to the clutch. I couldn't find a clutch/compressor at the local wrecking yard, so I just ordered a new clutch and it should have arrived today. $115. The red wire coming to the AC compressor DOES have power with the engine running. I tested the resistance across the clutch coil and got 3 readings: 3.8, 4.1, and 5.0 ohms. Not sure why the discrepancy, prob just my poor technique. I had a hard time reaching the wires at the coil, so I tested them at the connections at the compressor. Is this anywhere close to correct?

 

The clutch is held on by one nut. Ive seen it a few times where its just broken off on a customers car. I would change the field coil, pulley and clutch before i went and bought a new compressor. The pulley is held on by a snap ring and its the other half of the clutch mating surface. Pressure while running on the low side should be around 30 to 40, high side around 250 to 350, depending on outside temp, elevation and humidity. Both sides will be balanced when off, usually around 100psi.

 

Knowing that the compressor gets voltage greatly focuses the troubleshooting.

I should have been more clear for my picture request. I wanted a picture of the face of the compressor clutch to look for damage or something missing. To do this, you must have the front end on stands and must remove the plastic splash shield and possibly the driver's front wheel to get a clear picture of the clutch face. If there is nothing obviously damaged or missing on the clutch face, then measure (1) the clutch gap (see post #2) and (2) the coil resistance, and (3) test for lack of continuity of the thermal protector.

Did you test the coil resistance as described below?

 

Thx again. I did not measure the resistance exactly as described above, but it was kind of close. I will measure it again tomorrow exactly as above and pull it in the garage and access the compressor as described above. I will have the new clutch assembly by then and hopefully find that the guys as the shop were telling the truth: that I am missing the clutch plate and this turns out to be an easy fix. How difficult is it to remove the clutch assembly from the compressor shaft? Do I need a 3-jaw or a threaded bolt pulley puller? If it is really just the clutch plate, I am tempted to do the lazy thing and just bolt up the new plate rather than replace the whole clutch assembly. Will f/u tomorrow night...

 

Unfortunately, some shops either don't diagnose correctly or don't explain the problem correctly. It's always best to verify any diagnosis prior to buying parts and initiating work.

If there is nothing obviously missing or damaged on the clutch, then do all three diagnostic tests I mentioned. You may want to do them regardless.

 

Well, here is my picture of the AC clutch. It looks to me like the AC compressor shaft has sheared off. The new clutch I bought didn't come with a nut to secure the armature plate to the compressor shaft; it came with a bolt instead (different than the diagram above). Did some of the compressor shafts have a threaded receptacle for a bolt? Do you think the compressor siezed up and rather than the belt breaking, the shaft broke and the armature plate fell off?

 

If you have the Sanden compressor, which is likely, then it's time to shop for a replacement compressor.

Try to return the compressor clutch.

 

Well Ron, you were right. I was hoping to just jack up the car once and do everything this afternoon, but I should have done as you suggested and made a diagnosis before ordering parts. I talked to the guys at the auto parts store and I think I will be able to return the AC clutch. I removed the compressor and poured out the oil, only to find a bunch of metal shavings in the oil. I assume somehow the system got hot and disintegrated the compressor, making the shaft overheat and shear off. So now I am ordering a complete replacement system; compressor/clutch, accumulator/dryer, expansion device, PAG oil, o-rings, and condenser. Plan to flush the tubes and the evaporator, then take it into a shop to have the system evacuated and recharged. The job looks pretty simple really, except I am not sure exactly how to access the expansion device. Do I have to remove the whole HVAC box inside the car, under the dash? Also, do you think it is necessary to replace the evaporator (it is an extra $115)?

 

If you do a very thorough system flush, you may only need to replace the compressor, receiver/dryer, expansion valve, oil, and refrigerant.

The expansion valve is connected to the evaporator.

 

Thanks to all your help, my AC is fixed. I did the entire job myself and learned a lot in the process. New compressor/clutch, dryer/receiver, condenser, orifice tube, oil, o-rings. Flushed the old evaporator and hoses, rented a vacuum from autozone and recharged it myself. Runs great! thx again!

 

 

Congrats Man! Ronj@HT Is the man. We really do appreciate all your help ronj!!

 

^^ Honestly - this thread is like the epitome of how this forum should work. Intelligent questions with intelligent answers & strong follow-up and follow-through by the OP and RonJ ---- all leading to a successful repair. OP just saved himself about $800-1000 - incredible.