A/c electrical issues
Thread Starter
3rd Gear
Joined: Jul 2013
Posts: 3
Likes: 0
A/c electrical issues
So ive been trying to repair my A/c system on my 1989 coupe. The clutch clearly wont engage. I get no voltage at the a/c fuse or compresser. But as soon as i unplug one of the pressure cycling switches that are mounted on the front right wheel well, the A/C clutch engages. Everything is factory, has the electronic switches. Thank you in advance.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
The AC fuse should have 12 volts on it when the ignition switch is in Run.
Do your power windows work? If not something is wrong with the ignition
switch or wiring from the ignition switch to the AC fuse and the Power window
circuit breaker.
Here's a picture of the High pressure cutoff switch, Low pressure cycling switch
and High pressure fan switch.
Which switch are you saying when you pull the plug the AC clutch engages?
What color are the wires at the plug?
Do your power windows work? If not something is wrong with the ignition
switch or wiring from the ignition switch to the AC fuse and the Power window
circuit breaker.
Here's a picture of the High pressure cutoff switch, Low pressure cycling switch
and High pressure fan switch.
Which switch are you saying when you pull the plug the AC clutch engages?
What color are the wires at the plug?
Thread Starter
3rd Gear
Joined: Jul 2013
Posts: 3
Likes: 0
Double checked the plug going to the condesser has .5 volts and both the fuse in the fuse box and under the hood dont have any voltage. When i pull the cut-off switch the compresser engages then the radiator far engages
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
You have a 89 with the Auto Climate Control (C68) and not the
manual AC (C60)?
What you're saying makes no sense.
Here's the schematic.
If you have no 12 volts on the AC fuse with the ignition On. There is
no way 12 volts can get to the Clutch coil.
The AC High Pressure cut out switch and Low Pressure Cycling switch are
in series. They both must be closed for the clutch to engage.
High Pressure cut out switch is closed when the high side pressure is below 450 psi.
and will close when the pressure drops back down to 200 psi if it opens.
The Low Pressure cycling switch closes when low pressure is above 47 psi. and
opens when the low pressure is below 24.5 psi.
So if you're pulling the plug on the High Pressure Cut off Switch the clutch should
never engage.
manual AC (C60)?
What you're saying makes no sense.
Here's the schematic.
If you have no 12 volts on the AC fuse with the ignition On. There is
no way 12 volts can get to the Clutch coil.
The AC High Pressure cut out switch and Low Pressure Cycling switch are
in series. They both must be closed for the clutch to engage.
High Pressure cut out switch is closed when the high side pressure is below 450 psi.
and will close when the pressure drops back down to 200 psi if it opens.
The Low Pressure cycling switch closes when low pressure is above 47 psi. and
opens when the low pressure is below 24.5 psi.
So if you're pulling the plug on the High Pressure Cut off Switch the clutch should
never engage.
Last edited by Hooked on Vettes; Jul 8, 2013 at 08:41 PM.
