Temperature control question.

I got an 88 Formula 350, heres the situation: I had no vacuum due to a back intake manifold gasket, so I replaced it and I got vacuum back and my heat could blow again. But now it only works on 3 of the 4 fan speeds, if I put it on High it turns off, but the other three work fine. Anyone know what that is?

Sounds like a relay problem.

Sounds like the contacts in the control head to me.

probally a hole in your vaccum lines between the controlls and heater box. or it could be electrical.

I would check out all three of these possible causes...keep us informed.

it has a high speed resistor on the a/c heater case. usually under hood on the black plastic case near a/c heater is and the hoses go in. it is a little square piece with like a 4 wire plug and two screws holding it in