Hi there,
I have a 1992 Accord LX Manual (RH Drive). For the last few days i have been attempting to get the A/C going again. I started by finding out if the compressor will even engage and it does fine. But for some reason there was no voltage to the compressor. I discovered this to be caused by the relay not engaging because there was an earth fault caused from the HAC controller behind the dash. I have since then replaced this part but it is still not working so i have bypassed it for now so i can fix other problems. I have now got voltage to the A/C relay but for some reason when the relay engages, instead of the compressor coming on the cooling fan does. I thought this may have been due to a low voltage being supplied to the input for the compressor but i have seemed to have fixed this and now have 13.87 volts but still no compressor engagement. There is a full tank of R12 in the system and it was running fine. But now i have this new problem there is no engagement at all. Occasionally The low voltage comes back and reads out at about 9 volts, I have inspected the ICU under the right hand panel with all the fuses connected and there seems to be no problem with it that i can find. Any idea's on what might be causing this to be happening?

 

Your post is confusing.

If you are getting 12V to the compressor electrical connector (one wire connector), then the compressor clutch should engage. You said that it is not.

You said earlier that the compressor is engaging. Which one is it?

There is a ground screw on the compressor that you may want to clean up, then reattach.

 

I have a later model but had similar problems. I think you're saying that the compressor voltage varies from 9 to 13 volts. That makes me question the compressor relay.



Relays can check fine unloaded but fail when put under a normal load. If the voltage is 13 unloaded and the relay is bad the voltage could easily drop to the point that the compressor clutch won't engage. In my car's case both relays were bad so swapping them made no difference. Two new relays did. But I jumped the clutch and verified that the clutch/compressor worked before spending money on new relays.

 

The coil may be energized w/ voltage, but clutch plate fails to close. This happens when the clutch gap becomes too large, prehaps > 30mils. A good test is to thump the clutch plate hard w/ a stick (carefully!) and see if clutch engages.

If this works, the clutch gap must be reduced by removing a shim from beneath the clutch plate. It is possible to do in place w/o discharging the AC.

good luck

 

Hi,
The Voltage is varying, and is often too low at the positive side of the compressor relay. It's not an earthing problem as i have measured between the Positive terminal and the block of the engine and got a measure of 9 volts then a couple minutes later got 13 and it is the same between the two terminals for the relay. The compressor still engages fine as i have connected it directly to the battery and it clicks and the clutch engages. You can also check the voltage coming through the relay and there is no voltage loss, which tells me the relay, positive input and earth are fine even under load as the relays were changed for new ones and it made no difference. But what i don't understand is why, when there is voltage to the compressor through it's conventional line only the fan comes on and there is no engagement. But if you wire the compressor straight off the battery with the same voltage output it engages fine. I worded my original post a bit wrong. Sorry guys. Thanks heaps for any help though.

 

Variation in battery voltage either means poor battery connections or simply poor technique in measuring voltage. It's easy to get a poor connection w/ probe unless you push firmly.

If you suspect relay, suggest replacing or swapping w/ one of cooling fan relays (same I think).

ECM controls compressor by supplying ground to full-time energized relay drive. If relay is closing and no compressor action (clutch plate clamps closed), then either relay is not passing the voltage through relay contacts or clutch gap is too large as explained previously.

good luck