BrotatoChip

Hello, I have a 2002 Civic Ex. I bought this car at the beginning of last summer and the A/C worked fine. But now, as it is getting warm out, it stopped working properly. When the engine is cool, i.e. sat for a couple hours, the ac turns on and works fine. As the engine warms up and gets to normal temps the compressor shuts off and won't turn back on until the engine is cool enough again. I checked the psi in the system and it was around 44 psi which I believe is normal. Any suggestions are appreciated.

cal45fan

AC Compressor thermal switch might be bad.

ezone

My experience has been that if the thermal protector has been tripped, it won't come back to life on its own.



I'd wait for it to quit, then evaluate everything that is going on:

Are the fans still running? (Important part of figuring the next step!)

If the fans are still running as if the AC was still on:
Is the clutch getting powered up? Ohm check the clutch circuit WHILE it is quit, check from the relay socket.
Check powers and grounds at the relay socket, that tells me what MY next step should be.
Can the clutch be manually engaged with a jumper wire at the relay socket?


If the radiator fans are NOT running while the AC quits, then my checking would be towards the MICU and the HVAC control panel and those sections of the system.


Another of my first steps is to read PCM data list, see if it shows the AC has been requested by the MICU, and if the AC has been enabled and clutch relay engaged by the PCM.



HTH

BrotatoChip

Yes both fans turn on when I turn on the a/c, even if the compressor isn't working

ezone

Your problem is most likely with the clutch relay, the wiring to the clutch, or the clutch itself.

I'd start my testing at the socket for the clutch relay and see where that leads me.
The relay itself is a pretty darn popular failure here. IF it does turn out to be the relay, order this part number from the dealer 39794-SDA-A05 it is the updated relay. $25.25 USD



I'll add checking clearance of the clutch too.

BrotatoChip

Where is the compressor clutch relay located? I look in the fuse box under the hood and in the cabin

ezone

Engine compartment fusebox. If I could see the diagram, I could tell you which relay, I believe the only label is a plain snowflake symbol.


NVM, Google to the rescue:

BrotatoChip

Yes you are correct. The symbol is just a snowflake. Ok now that I know where it is how do I go about testing it. I've never done anything quite like that before

ezone

Easiest is to mark it, and swap it with an identical. If that keeps it working, you win. Swap it back, buy the improved relay for the clutch.


If that did not help, then do you have a test light?
Do you know how to use one?

BrotatoChip

I will try to test that sometime tomorrow, but I have two exams tomorrow so it may be tuesday. What do you mean by a test light?

ezone

Try to cram some practical DC electrical theory while you are at school.

http://en.wikipedia.org/wiki/Test_light


Store-bought test light:





Although, a simple 12V light bulb with 2 lengths of wire and a couple of roach clips attached could suffice.

BrotatoChip

Hey one of my exams is for Circuit analysis so this should help!! No i don't have one but i could find a light bulb and some wire around here somewhere

ezone

Use a small bulb like a #194 license plate light type, not a 55w Halogen headlight.

You could probably just buy a real simple one for like $5 or less if you look.


Although there is a practical use for a headlight bulb as a test light, it is not here.

BrotatoChip

Ok so what am I using this to test?

ezone

What does it take to light up that test light?
How can this be used?



WTF are you studying?

Electromechanical 12VDC is far simpler than electronics. I think you should have had some background in this as a prereq for an electronics course.

You need to know what a relay is, what it is used for, and everything it takes to operate one.
Once you understand all of this, then it should be easy to test....not only the relay, but logically figure out everything around the relay.

Then test for all of those things.

Is everything present that the relay needs, in order for it to operate?
If the relay operates, does the unit it controls operate correctly?


HTH

BrotatoChip

I swapped the relay for the compressor and the headlights. Compressor clutch didn't even engage

ezone

So it probably isn't the relay.

Continue testing.

Test, don't guess.

Biscuit

Apply direct power to the clutch from the battery.
If the clutch does not turn on you need a new clutch.

BrotatoChip

I found the problem.
I did this http://honda-tech.com/showthread.php?t=2041582
Airs not as cold as I would like but the a/c doesn't shut off now. If I replace the actual part instead of adding that resistor would the air get colder?

BrotatoChip

Nevermind. Worked fine the last two days after doing that but it shut off again after a 10 minute drive. Gonna test the compressor tomorrow.