Full charge but A/C compressor won't turn on
 

Like it says, just looking for some ideas, maybe fuses and relays which will be checked tomorrow. Other than that I don't know. I did a timing belt recently and that single wire that goes to the compressor was disconnected. It was very difficult to get back together but I did, however I wonder how reliable that connector is.

What MY are you working on? is the fuse good? Start simple. Disconnect the wire at the compressor clutch and check for 12VDC with the car running and A/C switched on. If no 12 VDC to ground check for 12VDC at the low pressure switch, then the anti-freeze switch in the cowl. If you get to the anti-freeze switch and still no power the issue is in the control unit in the cabin or wiring at the panel. If you have 12VDC at the clutch connection you either have a bad clutch coil or clutch coil ground to the compressor case. If the compressor is seized it typically blows the fuse when AC is switched on.

Hope this helps.

Mike

A typical failure is the relay inside the A/C head (post 29 or so here... also covered in many other threads): https://rennlist.com/forums/928-foru...c-leaks-2.html

On the other hand, if you're very lucky, it may just be a disconnected A/C switch. Check whether the clutch engages when you switch the controller to defrost. If it does, then the panel switch is bad or disconnected.

86 US model.

Where is the low pressure switch and the anti freeze switch? Also how do I test them?

So far I have tried to switch to defrost with no change, compressor clutch does not engage.
I have tested with the car running the DCV from the single wire leading up to the compressor from the harness to a ground point and got nothing.

Found a thread that explains how to test them and where they are so scratch that.

I have since tested the clutch by jumping the single wire leading from the clutch to the jump post and it clicked on.

I checked fuse #8 and it is in good condition. None of the relays on the main board seem to have anything to do with the a/c compressor, only the blower, which works. So I moved on.

I have tested the freeze switch as follows.
Start engine with a/c turned on.
I disconnected both connections.
I put one of the multimeter leads into each of the wires going to the switch to first find the power source, both times I used the crossbrace bolts as ground for the multimeter lead.

In doing this test on the freeze switch I came up with zero or next to zero, like .12V, so I feel it is safe to say I am not getting power to that point... if I havent done anything wrong.

What do you guys think? Head unit relay?

Probably

Probably? Was anything I mentioned incorrect and is there something else it could be?

I appreciate your help in this thread and even the others I have referenced but, I am obviously not an expert so "probably" sends me nowhere.

I think it's probably the head unit relay. It's possible, but much less likey, that it's a loose connector somewhere, a broken wire, an oxidized terminal, or a burned trace on on the head unit PC board.

If it were me, I'd pull the head unit, open it up, and see what I find.

If you have tested the wires that go to the freeze switch, with the ignition on, A/C on, then the HVAC head relay is shot. Now, you should check that both the head unit and the A/C switch are both plugged in. There is a chance that you knocked the plug off the A/C switch when you reinstalled everything.

Awesome guys, thank you, will report back.

Just confirmed that it is all plugged in.

Does the car need to be running for these tests or just ignition on?

Ahhh! The power of Rennlist. My AC quit working a couple of days ago. It bugged me, but I figured I'd get to it this weekend. Low and behold, I'm casual reading RL with a coffee, and I come accross this post. I hadn't thought about a separate circuit for the defroster ran the ac compressor... So I just went out to the car and started it up. Checked for AC again. nope. Slid the slider over to defost with the AC button depressed. Compressor kicked on. Defrost was hot. Slid the slider back to max AC and AC works!... I'm guessing it's the head relay being able to switch over easier since there is already current activating the AC clutch... It's my theory anyways. So thank you the idea SQLGuy!


My AC has been cool, but not been really cold however, so I'm going to try the foam AC filter cleaner trick and see if that helps the temp this weekend. Wow! Shark possession makes me look forward to weekends again!

Sorry to hijack the thread, but I figured it is related for future viewers of this.

Good luck with your fix. Did your AC work previously? Or are you trying to revive an AC system that has not run in a while?



:biggulp:

Ignition key on, no starting needed to test. Started to check to see if the compressor is turning.

Awesome, thanks Sean.

My A/C was like a meat locker before, Meteor. I've got a few hours to kill today so I am going to try and test this a little further and get to drive my car other than when its cool at night!