AC commpessor clutch proplem
Thread Starter
Intermediate
Joined: May 2008
Posts: 31
Likes: 0
AC commpessor clutch proplem
On my 87 auto, when I set my solid state ac climate control for ac the compressor clutch will not engage even when I jump the pressure switch .
I am getting 12 volts to the compressor and I know the climate control needs to send a ground to the compressor.I checked and see no ground on the black wire.The blower is working.
My engine is running and I set the controller to cold. When I physically ground the compressor myself, I blow the 25 amp fuse in the fuse box.
I have pulled the compressor connector off and attached 12 volts then a ground and the compressor engages fine.
What is wrong with the ground?
Is it a bad ECM?
A bad AC controller, it reads and lights up OK.
Bad diode on the connector?
Help.
I am getting 12 volts to the compressor and I know the climate control needs to send a ground to the compressor.I checked and see no ground on the black wire.The blower is working.
My engine is running and I set the controller to cold. When I physically ground the compressor myself, I blow the 25 amp fuse in the fuse box.
I have pulled the compressor connector off and attached 12 volts then a ground and the compressor engages fine.
What is wrong with the ground?
Is it a bad ECM?
A bad AC controller, it reads and lights up OK.
Bad diode on the connector?
Help.
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,074
From: Lansing MI
On my 87 auto, when I set my solid state ac climate control for ac the compressor clutch will not engage even when I jump the pressure switch .
I am getting 12 volts to the compressor and I know the climate control needs to send a ground to the compressor.I checked and see no ground on the black wire.The blower is working.
My engine is running and I set the controller to cold. When I physically ground the compressor myself, I blow the 25 amp fuse in the fuse box.
I have pulled the compressor connector off and attached 12 volts then a ground and the compressor engages fine.
What is wrong with the ground?
Is it a bad ECM?
A bad AC controller, it reads and lights up OK.
Bad diode on the connector?
Help.
I am getting 12 volts to the compressor and I know the climate control needs to send a ground to the compressor.I checked and see no ground on the black wire.The blower is working.
My engine is running and I set the controller to cold. When I physically ground the compressor myself, I blow the 25 amp fuse in the fuse box.
I have pulled the compressor connector off and attached 12 volts then a ground and the compressor engages fine.
What is wrong with the ground?
Is it a bad ECM?
A bad AC controller, it reads and lights up OK.
Bad diode on the connector?
Help.
Thread Starter
Intermediate
Joined: May 2008
Posts: 31
Likes: 0
AC compressor
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,074
From: Lansing MI
Ok 12 volts is not the same as able to illuminate a test light. You can have 12 volts and not be able to light a test light much less activate a compressor clutch. Assuming you have proper voltage/amps available at the connector, key on engine running, ac turned on, compressor connector plugged IN, probe the ground side of the connector with a test light, does it light up ???
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
The Dark Green wire is grounded by the Blower Control Module when the Blower Control Module receives the AC request signal on the Dark Green/Yellow wire.
Look at the two connectors on top of the evaporator housing. Those two connectors plug into the Blower Control Module which is located inside the evaporator housing. Verify the connector plug wires are not burnt and making good contact.
On one of the connectors will be a Black wire which is Ground for the Blower Control Module. On the same connector is a Dark Green/Yellow wire which is the AC request signal.
With the ignition ON, engine doesn't have to be running and temp set to 60F and Auto mode you should measure 5.5 volts DC or more on the Dark Green/Yellow wire when AC is called for. If you do and the Compressor Clutch doesn't engage the Blower Control Module is bad. This is assuming you have the Low Pressure switch bypassed which eliminates low freon and the connectors are making good contact.
Last edited by Hooked on Vettes; Sep 5, 2016 at 03:26 PM.
Thread Starter
Intermediate
Joined: May 2008
Posts: 31
Likes: 0
AC ground
The Black wire at the Compressor Clutch is the power source from the 25 amp fuse and not ground.
The Dark Green wire is grounded by the Blower Control Module when the Blower Control Module receives the AC request signal on the Dark Green/Yellow wire.
Look at the two connectors on top of the evaporator housing. Those two connectors plug into the Blower Control Module which is located inside the evaporator housing. Verify the connector plug wires are not burnt and making good contact.
On one of the connectors will be a Black wire which Ground for the Blower Control Module. On the same connector is a Dark Green/Yellow wire which is the AC request signal.
With the ignition ON, engine doesn't have to be running and temp set to 60F and Auto mode you should measure 5.5 volts DC or more on the Dark Green/Yellow wire when AC is called for. If you do and the Compressor Clutch doesn't engage the Blower Control Module is bad. This is assuming you have the Low Pressure switch bypassed which eliminates low freon and the connectors are making good contact.
The Dark Green wire is grounded by the Blower Control Module when the Blower Control Module receives the AC request signal on the Dark Green/Yellow wire.
Look at the two connectors on top of the evaporator housing. Those two connectors plug into the Blower Control Module which is located inside the evaporator housing. Verify the connector plug wires are not burnt and making good contact.
On one of the connectors will be a Black wire which Ground for the Blower Control Module. On the same connector is a Dark Green/Yellow wire which is the AC request signal.
With the ignition ON, engine doesn't have to be running and temp set to 60F and Auto mode you should measure 5.5 volts DC or more on the Dark Green/Yellow wire when AC is called for. If you do and the Compressor Clutch doesn't engage the Blower Control Module is bad. This is assuming you have the Low Pressure switch bypassed which eliminates low freon and the connectors are making good contact.
Thread Starter
Intermediate
Joined: May 2008
Posts: 31
Likes: 0
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Thread Starter
Intermediate
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AC working
I found that the AC compressor need a bit of gas to start, the pressure sensor up by the blower box reads pressure and below a certain point will signal to turn off the compressor.I pulled off and jumped this sensor with a paper clip and the compressor engaged. Then I added a new can of the refrigerant till it was empty as the AC blower was on . The AC works now and it nice and cold. Thanks everyone who chimed in!