Speedtoys

AC quit...odd, went to look for 12v, none, so next to add 12v to the circuit and see if compressor clutch fires.

Burnt fingers on both hands on the alligator clips.


The post at the pressure switch, is open to ground...that aint right...

Mrmerlin

The post at the pressure switch, is open to ground.

what does this mean?



That switch thats screwed into the side of the receiver dryer will close when their is enough pressure in the system to close it.
Do you mean that one of the terminals is shorted to the switch body? if so then the switch is bad.

Speedtoys

Its got no resistance, it'll heat up 12ga wire a LOT if you put power to it.

Its more than the 5w clutch would normally take...heh.

Look...electricity and me dont get along well, but I dont believe doing that should do much more than simply engage the clutch...normally...

IcemanG17

I don't remember precisely how, but there is a way to bypass the pressure switch to make your AC work

Speedtoys

Well ya, but thats not the issue. i just put 12v to the circuit at the switch, and instead of hearing the clutch click on, it moved enough current to burn and blister.

Majestic Moose

Good question. I was helping a member with their AC and tried jumping the compressor directly from the jump post and blew a 20A fuse in my jumper wire. We ended up bypassing the low pressure switch and it engaged just fine. Also tried jumping a known working compressor off the car (ran jumpers for power and ground) and blew a 20A fuse again. I have a relay set up on my car that is fused at 5A and it works (even 3A should be enough). I don't understand it.

Speedtoys

...I feel im about to be told by Merlin to stop workin on electrical things...hahaha

928NOOBIE

Test your freeze switch yet? I had to recently replace mine. Hook up multimeter..at normal temps...0 ohms resist..if no current will pass..replace that first..Roger has them.

Bypassing pressure switch on drier just make a jumper wire and connect the two wires going to the switch...

I think Roger has the pressure switches also..

Mrmerlin

I really dont understand what your powering and then blowing a fuse.
if you would post pictures it would clear up a lot of the mud.
You know clear as mud?

to check the compressor clutch you would unplug the wire just in front of the right cam cover, thats going to the compressor
then add 12V to the wire, get your 12v+ from the jump post, the clutch should click closed.

To check the pressure switch,, ( you will be laying on the ground infront of the car reaching through the grill to get to the switch)
the one thats screwed into the side of the receiver drier,
you need continuity selected , so the probes beep when touched,
unplug the wires to the switch then touch each pin if the system has enough pressure,
then the switch should be closed, so you would have continuity. and it would beep.

Next you would touch the body of the pressure switch and one of the pins you should not have continuity from switch body to either pin or the switch is bad

The freeze switch under the plastic cowl cover is tested the same way,
remove the wires then test for continuity, you should have it,.... unless the evaporator is fully iced over since its not running it wont even be cold.
If the freeze switch is open ( does not have continuity) then it has failed and should be replaced.

What am I missing here?

Majestic Moose

OK I have a jumper wire about six feet long with alligator clips at both ends and a fuse holder to prevent damage or burns in case there is a short in what I am testing. All we did was clip one end to the compressor power wire and touch it to the jump post and that blew the 20A fuse in my jumper wire. I do not understand it. It should engage the compressor clutch and draw two to three amps but it is acting like a short to ground. The problem was found at the low pressure switch which was found open. With the low pressure switch bypassed and AC compressor plugged back into the wire harness it engaged normally.

Test two was with the old AC compressor from my car sitting on the ground not installed. It was in working condition and I only replaced it due to leaks and the mixed results I've read about with DIY rebuilds. I expected to be able to hear a click and ran a jumper for ground from the case of the compressor to a strut brace bolt. Then clipped my jumper to the compressor power wire and touched the other end to the jump post. Again it blew a 20A fuse.

gomez123

It actually has resistance that's why the wire heats up. Like a thumb plugging a water hose. No resistance is a open circuit, would not short or heat up.

Majestic Moose

You have it backwards, a short is no resistance other than the wire itself which starts a runaway condition of heat which creates more resistance creating more heat until something fails, either the power source or the wire will melt through.

An open circuit is infinite resistance in practical terms.

Mrmerlin

If your testing the compressor clutch and blowing a fuse then the clutch is shorted to ground or your powering the ground wire

Speedtoys

another odd issue, my AC belt has kicked off.. hmm

Will look at it more later today.

Tom. M

Belt kicking off suggests the compressor is seizing at some point. My GT did this way back in the day... replaced the clutch assembly since the rubber that provides shock absorbing was shredded. Ran it for a while and it fragged again. This system had been converted to R134 at some point in its life..In the end, had to replace the compressor, while rebuilding all the lines/o-rings expansion valve etc...recharged with R12...good to go since then.