heater a/c control assembly
Thread Starter
6th Gear
Joined: Jul 2008
Posts: 6
Likes: 0
From: Hamilton OHIO
heater a/c control assembly
First time on the forum but a long time owner. The blower will not work at all on my 1988 coupe. I have replaced the blower motor but I have a feeling the heater a/c control assembly unit has malfunctioned. It is the electronic variety. Can anyone tell me what the symptoms of this unit going bad and is there a way to check this before throwing away $600. Thanks for anyone's advice.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Start by checking the Blower Motor connector. Old motors can draw a ton of amps and if the wiring is discolored, it's been dropping volts and it may have melted inside of the weatherpak. Otherwise, the '88 sends low voltage signals from the Controls to a Module on the left side of the Evaporator housing. The Module amplifies those signals and sends them onto the Blower. I'd check for battery voltage on the Module first - that's the red wire. Then check it's ground - black - it's spliced into the blower ground (though that splice is wrapped up in the harness) and it terminates on the frame not far from the blower motor. Finally, put the Controls on "1" and check the input at the Module. It's Brown or Tan (and with age, often difficult to distinguish from the ground) and at this setting, you should see 2.5 volts. Bump the controls up to "10" and that input wire should rise to 6 volts or greater. The output to the Blower is Purple or Black/Red or whatever is hot at the Blower. At "1" it should be about 4 volts; at "10", 12 volts. If you have the input (meaning the Controls are working fine) and nothing out, it simply needs a new Module. Used on all of GM's electronic units, it's about 100 Bucks. Try NAPA or any GM Dealer should have one or pick one up at a Boneyard.
Team Owner
Joined: Jan 2003
Posts: 20,322
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From: Summerland B.C. Canada
Thread Starter
6th Gear
Joined: Jul 2008
Posts: 6
Likes: 0
From: Hamilton OHIO
Start by checking the Blower Motor connector. Old motors can draw a ton of amps and if the wiring is discolored, it's been dropping volts and it may have melted inside of the weatherpak. Otherwise, the '88 sends low voltage signals from the Controls to a Module on the left side of the Evaporator housing. The Module amplifies those signals and sends them onto the Blower. I'd check for battery voltage on the Module first - that's the red wire. Then check it's ground - black - it's spliced into the blower ground (though that splice is wrapped up in the harness) and it terminates on the frame not far from the blower motor. Finally, put the Controls on "1" and check the input at the Module. It's Brown or Tan (and with age, often difficult to distinguish from the ground) and at this setting, you should see 2.5 volts. Bump the controls up to "10" and that input wire should rise to 6 volts or greater. The output to the Blower is Purple or Black/Red or whatever is hot at the Blower. At "1" it should be about 4 volts; at "10", 12 volts. If you have the input (meaning the Controls are working fine) and nothing out, it simply needs a new Module. Used on all of GM's electronic units, it's about 100 Bucks. Try NAPA or any GM Dealer should have one or pick one up at a Boneyard.
