joshster

Hello - I'm trying to figure out why my A/C doesn't work. The clutch works and if I apply 12v directly to the red wire going to it, the ac works fine, so the red wire to the clutch isn't getting power.

When I turn the AC on, the fan starts running, and the engine RPM changes. Any suggestions what else I should check? Thanks.

ezone

Locate the compressor clutch relay and swap with another like relay, see if the compressor kicks on.

joshster

I tried swapping the compressor and fan relays. The fan will run with either relay, compressor runs with neither.

ezone

Turn on the AC.
Remove the compressor clutch relay, use a volt-ohm meter to check the 4 terminals in the socket.
Should find 2 terminals with battery power,
1 that measures as ground (one ohm meter lead on battery neg post)
1 that measures about 3-4 ohms (one ohm meter lead on battery neg post).

Which is missing?



If you test at the pressure switch, is there a ground on both wires? (while connected to the pressure switch)

joshster

Top left is 14v, bottom left is no volts or ohms, middle is 14v, far right is 75 ohms, so looks like the 3-4 ohm one is missing.

ezone

Hold on, I can't see what you are looking at.
Let's refer to this diagram so I can tell what pins you are referring to.




Which relay is your car using?
Which terminals tested have what on them again?

Car was turned on and AC was turned on when you checked these?

joshster

Yes, car running, A/C on. It's the bottom one, so pin 2 is 14v, pin 1 has nothing, pin 5 is 14v and 75 ohms.

ezone

#3 has 75 ohms?

If you jumper #3 to #5 will the clutch click on?


-----------------------------

That one comes from the PCM.

Um..... Check this


If you test at the pressure switch, is there a ground on both wires? (while the wires are connected to the pressure switch)

Unplugged, is one wire grounded?
Does the other wire show 5 volts?

joshster

Yes, Sorry - #3 is 75 ohms.

Jumping 3 to 5 starts the clutch.

Car Running, AC on Unplugged, 1 wire has 5 volts, and the other shows grounded (2.85 milliohms)

Car Running AC on, plugged in, both wires show grounded (2.96 milliohms).

ezone

Something sounds screwy with the reading there, if it really had 75 ohms on the coil it shouldn't click on.
But it clicks on, so I'll focus on the lack of grounding on relay terminal 1

And you said the engine idles up when you turn the system on so the PCM must be seeing the AC request signal.......

I'd probably want to make sure the PCM is actually showing that it turned on the compressor clutch relay on a scanner data list (scanner is quick for me), and verify if it is outputting a ground on pin A17 at the PCM. The PCM can inhibit AC operation if it detects engine overheat and some other stuff, so I'd check my data real quick.

You can check continuity from PCM# A17 to the clutch relay terminal 1. (black/red wire).

joshster

No continuity from PCM# A17 to the clutch relay terminal 1. If I put a jumper wire in between, ac kicks on, so there must be a break in that wire. Any good way to fix that so it doesn't look like a total hack job?

joshster

It ended up being really easy to fix. I took the battery out and the 3 bolts holding the under hood fuse box in, opened the cover on the back and the broken wire was right there. It looks like a mouse maybe ate it apart, or it got pinched. Was enough slack in the wire to solder it back together and heat shrink it.

Thanks for all your help. It is most appreciated.

ezone

Right on! Thanks for the update