A/C problems... Jrichker/HISSIN50 please come in

[Stang8URMPRT]

Ok, so here's the problem. The clutch stopped coming on today. The a/c system is full. I checked voltage at the pressure switch with a/c on max... 13.5 volts... Jumped it, clutch doesn't come on still. Checked voltage at the clutch harness with a/c on... Only getting .30 volts. Unplug the harness and it goes right up to 13.5 volts. If I give the clutch power from the battery, it turns on fine. Now I pulled the positive wire out of the harness, and plugged it in by itself into the clutch, and gave it battery ground. Nothing. Plug the harness in without the power wire in there, and give it power from the battery, the clutch kicks on...? I would think if it was a short somewhere it'd pop the fuse, and it's not.

And help would be great.

Nick

 

[Stang8URMPRT]

ttt

 

[Stang8URMPRT]

ttt

 

[Michael Yount]

Nick - doesn't sound like a short to me - sounds like a discontinuity in the power wire to the clutch.

 

[Stang8URMPRT]

huh? lol. Whatcha mean by discontinuity?

 

[90mustangGT]

I agree. You don't have a short, you have a partial open. This means that voltage gets to the A/C clutch, but not enough current to operate it. Check your A/C relay. Trace to the sourse of the harness and test from there. Keep following up the line until you find the gremlin.

 

[86T-Top]

discontinuity - it means the line is open.
Somewhere in the power (positive) side of the harness the wire is open, with either a break in the wire, or an open switch.

When you say short, you are saying that a wire is grounding or making contact to something it shouldn't be. So if the power wire would have shorted, then your fuse would have mostlikely blown.

Do a continuity check from the last know point in the wire where there is 12V and the end that plugs into the compressor. You will probably find that the circuit is open. Go from there.

Mario

Mario

 

[Copperstang87]

haha the heckler is askin for help

 

[Stang8URMPRT]

haha the heckler is askin for help

haha! The Domestic E-thug is still on this forum!

 

[Stang8URMPRT]

Yeah, I went back outside and checked... I'm also thinking there is a break in the power wire somewhere. I will go out and look at it tomorrow and trace where it's coming from. Thanks a lot.

 

[HISSIN50]

Nick, I am not sure i completely follow so if this does not make sense, my bad.

grab your WOT relay. it very well could look like poo (it is under the inlet tube on the pass fender; the wires into the relay socket can get fried from heat). you should have 12 volts from the low-pressure switch coming into that relay (the relay opens at WOT) and 12 volts out to the a/c clutch. sometimes just manipulating the WOT relay will make it work for ya. that is a good sign of it being at least part of the fault.

if no go, go to the LPS (low pressure switch) on the pass firewall and check it out. you should have 12 volts in and 12 volts out (the 12 volts out goes to the WOT relay; the wires in that connector can also vulcanize).

that is where i would start. If I understood what was going on, this should help narrow it down.

good luck bud.

 

[Stang8URMPRT]

Thanks JT... I noticed that relay is "clicking" when I turn the A/C OFF. Dunno if it's supposed to do that or not. Also. The car "bogs" down when I turn the a/c ON, but the clutch doesn't come on. I would see why it would bog if the clutch did kick on... It's bogging about 100-200 rpm then comes back up. Should it do this even though the clutch isn't kicking on?

 

[Ranchero5.0]

If you are getting voltage with the compressor unplugged I suspect green death in a connector or a failing diode pack causing resistance in series with the coil resistance. With the coil unplugged you have an open circuit so the full potential will show on the coil plug. Once plugged as a complete circuit (12vdc to ground) you have two resistances (the coil and the problem) and you are reading the voltage between them. The problem is dropping the voltage availiable to the coil (coils are usually under 20 ohms resistance).

There should be a diode pack in the coil lead where it runs into the chassis harness.

Jamie

 

[HISSIN50]

if the clutch is not engaging, there is no extra load on the motor. Ergo, I dont see why the motor should bog. In fact, i would expect the revs to increase as it expects a load (if the puter is actually getting the signal that you are turning the A/C on).

IIRC, in terms of the A/C, that relay should act as if it is non-existant unless you have the A/C on AND are at WOT. Otherwise, the power goes through the common and NC terminal as if they were one wire (when at WOT, the relay energizes and creates discontinuity between the two). So your relay clicking at any time other than WOT would make me really check it out. if you start moving the harness around in your hand, the A/C might just kick on and work normal.

 

[Ranchero5.0]

Just read your 1:05 post. the bog could be from the coil loading down the electrical system. That would also cause the low voltage at the plug with it connectet. A resistance check of the A/C coil would eliminate that.

Jamie

 

[Stang8URMPRT]

Ok, so what do these diodes do????

 

[Ranchero5.0]

The diode is a one way check valve for electrical components (make sense?)

A heavy electrical winding in the coil will create an inductive load as the power is being released (the magnetic fields in the coil collapsing induce the voltage). It's a voltage spike and electircal systems don't like them so manufacturers put them on coil devices to block the spike from going back up the line and causing havoc. (the IAC has one too) The AC coil jumper wire from the coil to the fender well should have one inline. A continuity check will show if it's working (you will have no resistance through the device with the leads one way, but flip them and you will have infinate resistance.)

Make sense?

Jamie

Jamie

 

[Stang8URMPRT]

Gotcha. All this info is making me want to go outside and test it all now at 1:30AM. lol. It's also very discuraging lol. My fiance was in the car, and she is saying it's NOT bogging, but RISING... Like it should. So disregard the bogging down comment. It sounded like it was bogging, but she said it was rising.

 

[Stang8URMPRT]

Also... When we first went out there, I could jiggle the wires around at the connector at the clutch, and it would turn on and off real quick. It def. sounds like a wire issue, but now it won't do it. Just some more info.

 

[Ranchero5.0]

1:30am is a bad time to try and work on something. I'm working now (well, trying to avoid it) and we don't like to get into any really technical repairs in between 2-5am. Did rig out a 450lb 46.5kw motor from one press to another earlier when one crapped a shaft. The things we do so girls get thier Vickies catalogs on time.

Jamie