About 3 days ago, the air conditioner stopped working in my 94 Civic LX 4 door.

Unfortunately, due to weather, I have not been able to check extensively under the hood... but was taking a shot in the dark to see if anyone has anything on this...

The compressor does not seem to be engaging at all, and of course no cold air. Under normal working circumstances (and being a four-cylinder) there is a small but noticeable drop in horsepower when the A/C button is pressed and the compressor's clutch kicks in and loads the belt. This effect is gone. The A/C button's light still functions as it should, however I'm almost positive that this has no bearing on activating the appropriate relay. The Check Engine light is NOT lit, and the car otherwise functions exactly as it should.

Both my Haynes and Chilton manuals refer A/C problems to "A/C manuals" - something I cannot afford, or wish to get into if it goes beyond anything too simple.

I am not looking for a distinct solution at the moment, but would appreciate any advice as to "where to start looking". Any labor hours I can offset by doing some groundwork first would be great, if this turns into something I have to have service for. Or maybe it's just a simple matter of a fuse. Or perhaps this is something that's happened to many '94 Civics (such as my hot starting problem with the main fuel relay.)

What should I check/go/look at first?

Thanks much in advance for any information you could offer!

 

turn the a/c on and then test the red wire going to the compressor...
this will let us know if the compessor is getting power...

i suggest checking all ur fuses under hood and under dash FIRST.


also does the fans come on when the a/c button is on?

 

The fuse for the A/C is under the hood. The same 15 amp fuse runs the compressor clutch and condenser fan.

Check whether the belt for the compressor is still there. If the belt is gone the compressor may have seized up and broken it.

The light on the button has its own circuit. It doesn't tell you anything other than that the button is pressed.

Like 94 said whether the fan (on the condenser) comes on or not is an important sign. Also the idle speed should increase slightly when you press the button.

 

I don't know if there are any AC specific manuals here but you can look http://hondatech.info/downloads/Auto/Manuals/Civic/

 

Sorry for the late response, however I'm extremely appreciative for the quick and good advice you've fielded.

My schedule and uncooperative weather hasn't allowed me to be too thorough thus far, but I'll let you know what I've found out thus far:

I have pulled about half the fuses under the dash, but not all, as I do not have have a fuse puller and some are quite stubborn. The fuse block in the engine compartment, all have intact fuses, though.

The compressor belt is intact, spinning over the flywheel just fine. The bits protruding just inside the flywheel (I'm assuming that's the clutch) are not moving, whether a/c on or off. The condenser fan is fully operational in tandem with the a/c switch.

My Condenser fan fuse is listed at 20a, per diagram and what's in the corresponding slot. If it indeed is the same fuse as for the compressor as mk378 suggested, this is not the problem, as it's intact.

Tomorrow afternoon I plan to use my multi-tester on the red wire at the compressor, checking whether voltage is present or not.

I apologize for the piece-meal information, but I wanted to make sure you knew I appreciated your advice and am working, slowly but surely to a diagnosis.

Thanks so much for your help!

 

If you have power on the red wire-- test resistance from red wire to ground (key off), should be 3 or 4 ohms. That means the thermal switch and clutch coil are OK. If the coil is working the clutch still won't pull in if the gap is too wide. This is fixed by taking the center shaft nut off. Then the clutch plate (part next to the pulley) comes off and you can remove some of the shim washers on the shaft. When put back together the gap will be smaller and it should work.

If there is no power to the red wire, unplug the pressure switch on the line by the condenser and test the switch for continuity. No continuity almost certainly means no pressure because all the refrigerant has leaked out. Since it quit within 3 days, if you just re-gas it it's going to leak out rapidly again. Never ever use "stop leak". You will need some special tools to service the refrigeration system properly.

If pressure switch is OK yet no power to the red wire, the compressor relay could be bad, or (rarely) there's a problem with the ECU. The command to turn on the compressor passes through the ECU.

 

I've tested the wire, there is a disconnect mounted on the housing for the condenser fan, I pulled this connection and tested for 12v presence upstream of the compressor.
There is none.

I tested the compressor itself for resistance as suggested, downstream from this connector. The compressor has no resistance, or continuity. It is an closed circuit. I tested the connection (red) to the chassis of the compressor itself.

What little I do know about electricity tells me that the compressor's electrical system is fried, and the absence of voltage at the supply says that there IS a fuse blown, OR some component fried as a result of the full continuity in this circuit... (zero ohms)

Is there an inline fuse I might be missing?
I sure do not want to replace it until the compressor's been fixed, though.

Are my speculations correct based on this information?

Thanks again for all your help!

 

If compressor really was zero ohms it would've almost certainly blown the fuse in the fuse box, then the fan wouldn't work either. There is no other fuse.

Test the pressure switch like I suggested. I suspect the refrigerant is all gone. If that's the case look for a big hole in the side of the compressor or damage to the condenser by stones from the road.

Do not apply jumper wires to anything trying to make it work, it'll just cause damage.