Hello! I've been reading in this forum for awhile now and had to register today so I could ask for advice. My civic's A/C starting working intermittantly last summer. I took it to have it vacuumed out and then recharged andsince that point it hasn't worked at all. I bought a spare compressor and when I hook it up outside of the car, the cooling fans come on just like they should, only they come on whether the AC is on or off. I disconnect the spare andfans shut back off.I jumpered the thermal switch on the compressor still in the car and the clutch/cooling fanskick on and the AC gets ice cold very quick. I could leave it this way, only the clutch stays engaged all the time, even if the AC is turned off. Without this jumpered, the clutch/cooling fans won't come on with the AC at all. My theory is that something is keepingpower going to the clutch all the timewhich in turnburned out the thermal switch sometime last year leaving me with 2 issues. I'm opento any and all suggestions as I have an appointment with a honda dealer this wednesday and am trying everything to prevent this very expensive option. Thanks!Matt

 

Unhook the new external compressor to bring system back to stock. Then, see if you can retrieve a DTC:

(Edit: Are either fuse 1 or fuse 14 blown? Have you tested the compressor clutch relay?)

 

I checked and just rechecked all fuses and relays in the system and all are in working condition. I ran the diagnostic and had no flashing light to indicate any problems.

 

Why don't you think that the problem will be fixed by replacing the thermal protector? Why not try swapping the thermal protector in the old compressor with the one in the new compressor?

 

Before I replace the thermal protector, I want to fix the issue of the AC staying on all the time. As I mentioned before, when I plug the other compressor in, the AC gets power all the time, even if the AC is shut off which is the same as the compressor thats currently in it with the jumpered thermal protector. I know the thermal protector isone of the issues, trying figure out why the compressor clutch is engaged all the timeand not with the AC switch.
Matt

 

Does the A/C run independently of the blower motor?

Look for a shorted/damaged wire between the ECM and heater control panel:

 

It's OK to jumper the thermal switch for testing purposes. I think Ron's diagram isn't exactly what you have. Some models have the thermal switch connected directly to the clutch as shown and others have low-level wires that go into the control system from the thermal switch.

When you have that latter system and there is a short to ground in the thermal switch or it's wiring the compressor and fans will stay on all the time. The way it works is the A/C control panel pulls the blue wire on pin 4 to ground to demand A/C (control panel checks that interior fan on, driver has pressed the A/C button, and the evaporator temperature is above 40 F). This signal passes thru the thermal switch and the pressure switch to the multiplex control unit. The multiplex control unit sends a command to the ECM. If the engine is running at a proper RPM, the ECM then closes the compressor and fan relays.

Check for shorts to ground on the wire between the control panel, switches, and multiplex control unit. If you can unplug the control panel (disconnect battery first since there is a computer in it) and the A/C stops, the control panel may be bad.

 

The diagrams were taken from the 02-03 Civic service manual:

http://hondatech.info/downloads/Auto/Manuals/Civic/

The same manual shows the thermal switch associated with the compressor:

 

I made the appointment for tomorrow, I will post back tomorrow with the results. I have a feeling it's either the ECM or the multiplex unit itself. Thanks for all of the replies and suggestions!
Matt

 

One more question just to make sure I jumpered the thermal protector correctly. I hooked the 2 wires together that are not the clutch power wire. When I hook these together, the middle wire gets 12V positive and the clutch engages. Thanks again.
Matt