Okay, I had an earlier post about a faulty A/C system. I traced it to a faulty ECU, and replaced it. Immediately, the A/C worked. Drove it for 2 days, and it was fine.

Started the car today, and nada. No condensor fan, no compressor clutch. Now I start with the Honda Service Manual, and do the troubleshooting guide starting on page 907... never expected it to have an error. On page 909, it asks you to check for continuity in the blu/red wire between the condensor fan relay and the pressure switch. Problem... my car does not have a blue/red wire between the pressure switch and that relay... it is yel/white. The blue/red wire goes back towards the ECU. Now, on page 915, same problem... no blue/red wire going to the relay. Is my car wired wrong, or is the manual wrong? Funny thing is, if I ground the yel/white side of the pressure switch, the fan comes on... I ground the blue/red side, the compressor comes on, jump the two, and nothing.

Even the diagram on page 907 shows a blue/red wire going into the condensor fan relay... no such critter in my car, it's yellow/white.


Suggestions or comments?

 

What manual are you using? The 92-95 Civic manual is actually a 92 Civic manual. As the 92 Civic has an R12 A/C system whereas the 94 Civic has an R134a system, some changes may have been made in the A/C circuit.

Here's the circuit diagram for the U.K. version of the 95 Civic (not sure if other elements of the diagram pertain to your 94 Civic):

 

Check at the thermostat, which is mounted on top of the evaporator case. Remove the glove box to access it. Check that its blue/red wire goes to ground when pushing the A/C button with the interior fan on at any speed except off. If it doesn't there is a problem in the control panel. Then the yellow/white wire should go to ground too, and this will engage the condenser fan relay and signal the ECU thru the pressure switch to engage the compressor.

 

Why not first try jumping the A/C thermostat? If the A/C now runs with the thermostat jumped, then the thermostat itself is probably bad.

 

Ron, I am using the manual that I downloaded from the link in your sig. The above diagram is exactly like my car's wiring, not what is in the other manual. Do you have that manual available for download? Looks like it is more correct for my car. I will try jumping the thermo switch first.

UPDATE:
Well, I went out to try to jump the thermo switch, and the dang AC was already working again. I am totally confused now. Can the air temperature cause the thermo switch to stop the ac from working? When I was working on it today, it was HOT (94 degrees) but when I went out tonite, it was relatively cool (78 degrees.) Can this be the cause or do I just have a haunted car?

Ron, I would love to get a copy of that other manual if you have it please sir!

 

I guess your confusing finding may be consistent with a faulty thermo switch, but do verify by jumping. This would be done by jumping both the thermo switch BLK/YEL and YEL/WHT wires to the thermo switch BLU/RED wire. Jump the wires only briefly as the thermo switch protection is absent.

The manual from which the diagram was taken can be found at the same link in my signature. It's the Honda Civic 95-97 manual.

 

I will try that tomorrow. Thanks.

One thing I was also concerned with, does the a/c on/off switch ever malfunction? I read somewhere that sometimes high cabin temperatures can cause the switch to malfunction after years of use, and it will short, causing the ac not to work. If jumping the thermo doesn't work, I will check for signal from the on/off switch. Maybe it's as simple as the dash heating up and losing contact in the switch or a broken weld on the switch? I guess I have alot to test tomorrow!

Thanks.

 

SOLVED!

Well, last night (76 degrees) when it was cool, the ac worked again...

This afternoon (92 degrees) of course the ac did not work! I started with the ac thermo switch, and yup, it passed. Jumped it and ac turned on. Proceeded to pull out the climate control panel, and jumped the blu/red wire... yup ac turned on. Took the climate control panel apart, and inspected the ac switch... found a cracked and loose solder point, you guessed it ... in the circuit to the ac termial on/off switch...

I soldered the point, reassembled the climate control panel, and voila.... ac kicked on as it should. I added some R134 and now it blows cold air!

Lessson learned... Even if the switch lights up green when you push it, it doesn't mean it's actually working. Appearantly, when the the interior temperature gets very hot, the climate control panel overheats. This causes the circuit board to deform slightly, eventually breaking the solder point on the switch. When the car cools, it regains contact, and works intermittantly. This whole learning process cost me about 40+ hours of tracing wires, internet research, and about 10 gallons of sweat.

Thanks to mk378 and RonJ for all the help. Maybe this will eventually ease somebody else pain with the same symptoms.

John "Trouper" Troup

 

Congrats on the fix! You should be proud of the fact that many people would not have been able to figure out this complicated troubleshooting problem. (The exception, of course, would be mk378. He seems to be our super-A/C expert.)

 

Thanks a lot!!1 you saved me a lot of hours of frustration and work, this was my problem too, im glad i found this post.