Hi guys,

2001 Civic EX coupe auto

I am new here and in need of help. The problem is the AC clutch will not stay engaged. I did some troubleshooting this morning. The relay is good and no fuses blown. When the car is running cold, the ac clutch engages but if you accellerate the motor, it will release and stop compressing. I pulled the relay to the compressor and jumped the #1&2 posts giving it full power. Then started the car and rev'd the motor. The clutch engaged and stayed on. So its not a compressor/clutch issue. For some reason the circuit is disconnecting as the engine warms up and when I rev the engine. Is it an ECM problem? Broken wire? How do I restore full power to the compressor clutch?

Thanks
Matt

 

The problem may be due to too little or too much refrigerant or air in the system. Also measure the gap between the compressor pulley and the clutch armature plate.

 

QUIT JUMPING STUFF. You'll blow your fool head off.

Do both radiator / condenser fans work? It is probably tripping off on high side pressure like Ron suggested. Naturally, measuring both pressures would help in the diagnosis.

 

It's worked fine for the past 3 years and still runs until I accellerate. Also, once the car is hot, it just won't engage for the most part. The fans do come on and stay on. Using a low side gauge it starts at 60#(compressor off) and drops to 15-20#(compressor on) before kicking off. Does that mean I'm low on freon? Sorry, but I don't have a guage set with the high side connection.

 

Haha mk. You've pulled me up in the past for making a similar suggestion. Maybe the pressure relief valve on the compressor will save him.

OP - get a manifold gauge set and measure both the low and the high side pressures with the engine rpms at about 1500 rpm.

 

If it were "low on freon," the compressor would just stay engaged constantly.

Another possibility is that the evaporator is getting cold, causing the compressor to cycle off normally, but then the clutch gap is too wide so it won't re-engage. In that case the fans would restart but the compressor won't.

 

I forgot to mention this. When the compressor kicks off and won't re-engage, if I wack the clutch plate with a rubber mallet, it engages again. What's up with that. It can't be a weak coil because it holds when I jump it at the relay. Right?

 

The A/C pressure switch is a dual low and high pressure switch. It will shut the compressor off if the refrigerant charge/pressure is either too low or too high.

 

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...except that the switch is on the high side, so once the compressor starts with a low charge, the pressure there will rise and keep it running. If very low the switch will be open and the compressor won't start in the first place. Except maybe after the car warms up and expands the gas a little. Which is the opposite of what the OP is experiencing.

Anyway the OP just told us that the clutch gap is too wide. All that he or she needs to do is take the clutch plate off, remove some shim washers, put it back on and enjoy the rest of the summer.

When hit with a mallet (which is a legit and reasonably safe test, compared to jumping the relay with the engine running), the plate moves close enough to the magnet to get pulled in again, for one cycle. The magnet is more powerful when it is cold (lower resistance of the copper windings). So that's why it can pull in by itself when cold but not when hot.