Throttle sticks when using defrost

[TwoFiftyShifter]

Not sure about this... PO put a new heater control in. I don't see where the throttle cable is binding. Seen this before? Quadrajet carb and an AC truck but compressor isn't hooked up.

[bigdaddy4x4]

if your truck has a/c it has a idle compensator hooked up to the carb.so it comes on when changing over to defrost if your a/c works i would keep it on there. if not just unplug it its has green wire going to it

[TwoFiftyShifter]

Found it. Fixed. I guess an AC compressor really chokes out these old trucks huh?

[Axle]

A carb does not have the luxury of adjusting on the fly.

[TwoFiftyShifter]

Actually its still sticking after unplugging that compressor wire. The search continues

[Dead Parrot]

Might make sure the cable for the heat/cold flapper didn't get ran around the throttle cable under the dash when the PO replaced the heater control. Or a random wire bundle that moves just enough when the heat is on. IIRC every thing else is vacuum controls.

[Axle]

Originally Posted by TwoFiftyShifter

Actually its still sticking after unplugging that compressor wire. The search continues

Look at the throttle side of the carburetor, do you see a solenoid with a single wire plugged into it? Thats the idle stop solenoid, on ac vehicles that kicks on with the a/c to increase idle to compensate for the increased load. Unplug that solenoid and see what happens.

Alex.

[1976gmc20]

I must admit that when I first saw this thread, I thought about the "throttle stick" that I would wedge between the seat and the gas pedal to keep my old pickup running while it warmed up

[TwoFiftyShifter]

That's funny. Axle had it right. I pulled that wire and it doesnt stick now. I assume if I had a belt on the compressor I would need to plug it back in to use defroster