denb23

Ok. I took my car to my mechanic (electrical is not his strong suit as he admits) and he took a gander with what was causing my AC not to work. I have a 2000 Civic EX. He determined that the compressor wasn't the problem and was convinced it was the switch that was bad so he found a new switch. He replaced that, but still couldn't get the compressor to turn on. So, his theory is that there is a "bad ground" somewhere.

I had my brother look at it yesterday who is pretty good with wiring and good with cars although not a professional mechanic. We tested the "a/c clutch" and it works. We tested the relay at the fuse panel and it was working. We tested the switch and it works. So, what he did was jump with a wire from the relay all the way to the compressor and that got the compressor to turn on. So, his theory is that there is no signal coming from the ECM to the relay at the fuse panel or that there's a bad ground. Does anybody have any solution for this? Should I have my mechanic hook the ECM up to his reader to see what codes are coming up to better gauge what to fix? Or, do something else. Any help would be greatly appreciated. Thanks!

Dennis


Modified by denb23 at 12:03 PM 6/8/2008

denb23

Can anybody help me with this?

duggy

by "switch" do you mean the switch inside the cabin where the climate control is, or the pressure switch?

denb23

It was the pressure switch-the switch directly next to the compressor.

denb23

Here's his entire explanation per an email he just sent to me:

I tested the compressor clutch relay. The relay worked properly out of the circuit with 12VDC and ground applied to coil from the battery via jumper wires. Loud audible click is heard and contacts close properly when voltage is applied to coil of relay.


On relay connector, 12VDC is being properly applied one side of the contacts and coil of the relay as it should (see schematic). During normal operation, contacts of the relay supply the 12VDC to compressor clutch when relay is energized (see schematic).


When relay was placed back in circuit, engine running, and AC turned on, the relay clicks FAINTLY and contacts do NOT close. Schematic indicates that ECM applies ground to coil of relay to energize relay when AC is turned on. Because relay is not energizing I suspect the ECM is not sending the proper ground signal for some reason. I don’t have equipment to test ECM so that’s the most I can tell you. The likelihood of the wire between the ECM and relay having too much resistance is slim so I didn’t test that.


I jumped right from the battery to compressor clutch with a jumper wire and the compressor clutch engaged with engine running.


Enclosed is the schematic.

denb23

Anybody have any suggestions? Please I need help with this!

itsmejto

There are two safety presure switches, one for low, one for high, both should be normally closed, if the presures are too high or too low, then the system may be over or undercharged. get a cheap gauge from an outoparts store, some come on cans of r134 which you may need anyway. Check the static presure on the low (fat pipe) blue connector, it should be 70psi+ on a warm day, if its low then you may need a shot of 134a. Usually if a system is overcharged, it will run for a few seconds before the high presure switch kicks it off, so my guess is it may be a tad low. Or it may be a faulty hi/lo presure switch itself, the faint relay clicking tells this tale too.

Mazhar Patel

Hi Denb23,

I am having the similar issue on Acura CSX a/c. Do you remember what was the fix for your car?

Any suggestions would be highly appreciated.

Thanks

94CivicSi

iTrader: (1)

If I recall, a failed a/c receiver dryer caused a similar problem on my Civic. It contained a pressure switch that failed, then would not allow the ecm to turn the system on.

Beev

My experience may contribute to your decision making.

I had a working A/C, but not a properly working '94 Accord LX. :-)

I replaced the 37820-P0B-A50 ECU with a 37820-P0B-A51 ECU from the junkyard (direct replacement upgrade to 37820-P0B-A50).

The car runs great now .... but the A/C does not work. I put the 37820-P0B-A50 back in and the A/C worked again, but the car ran poorly. I am going with the 37820-P0B-A51 and will look at the circuit board for a bad component....but, not until the car passes CA smog which the 37820-P0B-A51 pretty much assures.

I hope this was helpful. Good luck!