Air conditioning compressor electrical

[hanger]

Is the a fuse that solely controls the Air conditioning clutch? My compressor clutch won’t kick in and there is no power at the compressor clutch wire when I test it. The low pressure switch has continuity but there is no power going to the switch. I can put a jumper wire on the compressor and it will engage and blow cold air.

[tgreese]

Year/model/equipment? I'd look at the wiring diagram for your year and trace back the wires.

Similar question here - viewtopic.php?f=10&t=22571

[hanger]

Year/model/equipment? I'd look at the wiring diagram for your year and trace back the wires.

Similar question here - viewtopic.php?f=10&t=22571

Oops. 87 GW.

[89_Wagon]

Is there power going to the switch? The switch is in series to the clutch. How's the condition of the wires themselves? Continuity between the clutch connector and low pressure switch?

My '89 has a control box that monitors some inputs, including the thermistor, and that module sends the signal to the AC to clutch to turn on. Your '87 might be the same.

[hanger]

The LP switch has continuity but no power is going to the LP switch. If I put a jumper wire from the battery to the LP switch clutch wire the clutch engages and starts cooling. I suspect the thermistor is bad because the system started having problems with the compressor kicking on for 5-10 seconds and then disengaging for about a minute before kicking on again for another 5-10 seconds.

[89_Wagon]

That sounds like normal operation if you're not on max cool. That's how the system controls AC temp... it just cycles the pump on and off.

Is it doing that on the max cool setting?

[hanger]

That sounds like normal operation if you're not on max cool. That's how the system controls AC temp... it just cycles the pump on and off.

Is it doing that on the max cool setting?

Read my post again. You missed some important information.

[89_Wagon]

I understood the original post. I'm trying to confirm it's not something simple that could save you some time.

It won't have 12+ unless the module or control mechanism requests the clutch turn on. The module sends the 12v to the LP switch, then to the AC clutch. The circuit is grounded through the body of the compressor.

Are you testing this on max AC setting? If it's doing that on max AC, then I would agree it's likely something else. I posted up the thermistor values on IFSJA.org some time ago. I don't think direct replacements are available but you should be able to find a generic one that matches the specs enough.

Here's a link to the page you need to diagnose the AC circuit. No relay. Looks like your year uses a module so all above applies to your year.
https://oljeep.com/gw/elec/87/87GW_Section14to26.pdf

[hanger]

It doesn’t come on at all anymore on max or otherwise and there’s no signal at the LP switch coming from the module.

I’m gonna make sure the wire in the loom inside the engine bay isn’t broke and then I’m going into the module.

Does the bezel around the dash unsnap like the Haynes manual states it does?

[devildog80]

The LP switch has continuity but no power is going to the LP switch. If I put a jumper wire from the battery to the LP switch clutch wire the clutch engages and starts cooling. I suspect the thermistor is bad because the system started having problems with the compressor kicking on for 5-10 seconds and then disengaging for about a minute before kicking on again for another 5-10 seconds.

Throwing in on this.....

Sounds like your freon is low (?), and when the clutch engages it will sense low pressure then kick off, and takes that minute before it tries again.

I would check for a leak, could be anywhere on any fitting, but would start with the fill connectors.

The little fill valve cores can get something stuck in the rubber seal, or simply fail, and will leak very slow.

Just a couple drops of good dish soap in a small spray bottle, and hit connections one at a time, then wait for the bubbles.

If not that, THEN I would venture into the wiring system.

[hanger]

The LP switch has continuity but no power is going to the LP switch. If I put a jumper wire from the battery to the LP switch clutch wire the clutch engages and starts cooling. I suspect the thermistor is bad because the system started having problems with the compressor kicking on for 5-10 seconds and then disengaging for about a minute before kicking on again for another 5-10 seconds.

Throwing in on this.....

Sounds like your freon is low (?), and when the clutch engages it will sense low pressure then kick off, and takes that minute before it tries again.

I would check for a leak, could be anywhere on any fitting, but would start with the fill connectors.

The little fill valve cores can get something stuck in the rubber seal, or simply fail, and will leak very slow.

Just a couple drops of good dish soap in a small spray bottle, and hit connections one at a time, then wait for the bubbles.

If not that, THEN I would venture into the wiring system.

That’s what I thought but there is no signal (power) coming from the module.

[devildog80]

Does the module require a signal from the pressure switch to allow it to energize?

That was my thought on low freon, as you would be at a low pressure situation, and the system checks kicked in to keep from turning on and burning up the compressor?

Like an engine low oil pressure switch, if not sensing oil pressure, will not allow engine to start or will shut it down.

[hanger]

Does the module require a signal from the pressure switch to allow it to energize?

That was my thought on low freon, as you would be at a low pressure situation, and the system checks kicked in to keep from turning on and burning up the compressor?

Like an engine low oil pressure switch, if not sensing oil pressure, will not allow engine to start or will shut it down.

No. The signal comes from the module to the LP switch. If the system is low on Freon the switch cuts power. I’ve bypassed the LP switch jumping off the battery and the system blows cold air.

[devildog80]

It does, but you stated a minute between 5-10 seconds of cold....ok

Were you able to find wiring diagram?

Brain still thinking, and trying to help if I can

[89_Wagon]

ok, now we're getting somewhere. I think the module itself is in the driver's footwell area, not behind the dash. That's probably the easier way to test the thermistor. That way, you avoid dropping the AC system too.

You should be able to test some of the other inputs as well from there. It'll be cozy in the footwell area while you prod around with your multimeter!

[hanger]

My Haynes Shop Manual shows the air conditioning module to be built into the selector and temp control on the dash. From what I’ve researched so far the thermistor is in the evaporator.

[89_Wagon]

Yes, the thermistor is in the evap housing. But, the wires run to the module. Up to you if you want want drop the housing to test the thermistor. There are pros and cons either way you go.

Weird, my AC module is near the steering column. It's a little black box.

[hanger]

Yes, the thermistor is in the evap housing. But, the wires run to the module. Up to you if you want want drop the housing to test the thermistor. There are pros and cons either way you go.

Weird, my AC module is near the steering column. It's a little black box.

Well now you have me thinking about where my AC Module is located. I assumed it was in the temp selector controls as the Haynes manual showed pictures of how to remove the temp selector controller and stated to unplug the AC Module. I took this to mean that’s where it was located.

What exactly does the AC Module look like?

[hanger]

Found this from a search.

https://fsjnetwork.com/forum/viewtopic.php?t=5165

[89_Wagon]

Here's another about the control module location. Not sure if your year is different.

From thread... "mounted to right rear edge of AC duct on driver side."

http://ifsja.org/forums/vb/showthread.php?t=177359