73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: doneebaker on February 14, 2026, 04:52:36 pm
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Hello folks , new user here. I have a 74 c10 with a/c that I cant get the heater motor to do anything. It will run on slow mode when I turn on the key but nothing else. While poking around in there I see an orange wire hanging from the hvac vacuum switch on the right side of the controller just hanging there not connected to anything and I can't see any other wires hanging down it should be connected to. I assume that it needs power but we all know about assuming things. Every thing else is intact. So if anyone would know where that wire goes to or what it is connected to that would be a huge help. I tried to find diagrams online but no luck. Thanks in advance for any help..
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This is exciting! It's been quiet around here lately. Welcome to the Forum! (Que the music Zieg!)*
Using a test light, does the "dangling" orange wire probe battery voltage (B+)?
Assuming factory A/C, is the 4-wire harness with brown, yellow, light green, and light blue wires plugged into the blower switch (see attached diagram)?
Does the brown wire connected to the blower switch probe 12 volts with the ignition switch on?
* Inside joke...