Heater switch

[CARS78MD]

THE HEATER FAN SWITCH IN MY 1978 CORVETTE WORKS ON THE FIRST THREE SETTING FINE , THEN ON THE HIGH SETTING SOMETIMES IT WORKS AND SOMETIMES IT DON"T..ANY IDEA"S

[TimAT]

Wiring to the high blow relay. Probably a melted connector. Turn the key on with the blower set to "hi", shake the wires to the relay. Poke around, it will appear. ''

Wiring Diagram:

http://www.nrjvette.com/johdotukset/...tte%201978.pdf

Edit- I just looked at that WDM for a '78. It does not show a relay, but I've seen them on just about every GM car made until they went the electronics. Dollars to donuts it's there.

[bill81vette]

I believe the blower has a resistor on it near the blower motor.
sounds like you have a loose wire,a ground,or switch...

[Peer81]

I have the same thing. I think it's the relay. Simple take it apart and see if it still can switch when powered.

Greetings Peter

[berry1133@bellsouth.net]

Where is the location of the relay?

[Peer81]

Right in plain sight. Against the firewall between the AC box and the distributor, you can't miss it!

Greetings Peter