Ok guys when running a Diagnostic on an 88 vert C68 electronic A/C system it reads a code of (-01) which translates to Feedback Potentiometer-open. What has happened the compressor will not engage. The system is charged so its not low bypassed the pressure switch still no compressor engagement so i ran diagnostic on the system and came up with the feedback potentiometer thing. Can anyone help me understand more on this situation what exactly do i have to replace and so on ? Appreciate the help.
A/C question
- Thread starter cajun86
- Start date
Ken
Gone but not forgotten
Bumped to the top in hopes of getting you an answer this time around. 
E
ecss
Guest
I'm looking at the schematic for a 89 so hopefully 88 has the same color code for the wiring harness. The compressor /clutch and control head are the same for both years.
Make sure the A/C 25 amp fuse is good. It's located on the end of the passenger side dash fuse box.
At the A/C Clutch connector, One wire is Black/White and should have 12 volts on it at all times. The 12 volts comes from the A/C 25 amp fuse.
The other wire is Dark Green and is grounded by the Blower Control Module when the clutch is supposed to engage.
On top of the evaporator housing there are two connectors going to the Blower Motor Control Module.
Connector C1 and connector C2.
Connector C2 has a Dark Green/Yellow wire going to it.
When the engine is running and A/C is on, you should measure 12 volts. This is the signal to the Blower Control Module to ground the Dark Green wire of the Clutch.
If you don't measure 12 volts, remove the connector at the High Pressure Cut out switch and use an ohm meter and measure across the switch. It should be close to zero ohms. Also do the same for the Low Pressure Cut out switch. Both switches should be close to zero ohms. If not the switch is bad or you're low on freon.
If the switches are ok, something is wrong with the Control Head.
On connnector C1 you should measure 12 volts on the Red wire. It's hot all of the time. This is the power source for the Blower Control Module. If the blower motor works, no need to check for 12 volts.
With the plug at the clutch disconnected, the resistance of the Clutch coil should be around 3 ohms.
Also verify with an ohm meter the diode that is across the Clutch coil is good.
As far as the code you pulled, the A/C clutch should still engage.
The diags. are very primative and don't tell you much.
Make sure the A/C 25 amp fuse is good. It's located on the end of the passenger side dash fuse box.
At the A/C Clutch connector, One wire is Black/White and should have 12 volts on it at all times. The 12 volts comes from the A/C 25 amp fuse.
The other wire is Dark Green and is grounded by the Blower Control Module when the clutch is supposed to engage.
On top of the evaporator housing there are two connectors going to the Blower Motor Control Module.
Connector C1 and connector C2.
Connector C2 has a Dark Green/Yellow wire going to it.
When the engine is running and A/C is on, you should measure 12 volts. This is the signal to the Blower Control Module to ground the Dark Green wire of the Clutch.
If you don't measure 12 volts, remove the connector at the High Pressure Cut out switch and use an ohm meter and measure across the switch. It should be close to zero ohms. Also do the same for the Low Pressure Cut out switch. Both switches should be close to zero ohms. If not the switch is bad or you're low on freon.
If the switches are ok, something is wrong with the Control Head.
On connnector C1 you should measure 12 volts on the Red wire. It's hot all of the time. This is the power source for the Blower Control Module. If the blower motor works, no need to check for 12 volts.
With the plug at the clutch disconnected, the resistance of the Clutch coil should be around 3 ohms.
Also verify with an ohm meter the diode that is across the Clutch coil is good.
As far as the code you pulled, the A/C clutch should still engage.
The diags. are very primative and don't tell you much.
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