Canada Rocket

Help! I have a 1972 Corvette that the heater fan doesn't work. This is what I know,
1) the fan works if you run 12 volts directly to the fan
2) I have power at the fuse
3) I have power to the brown wire at the switch
Does anyone know how to test the switch? Is there another thing that I should check? Thanks for the help!

Peterbuilt

http://willcoxcorvette.com/popup_image.php?pID=27790

spjrr

Hey Rocket, Had same thing on my 69 and it turned out to be a bad fan relay. This is a pretty common thing on these old gm cars have had same problem on other gm cars of that era. In the case of my 69, I bent the cover tabs on the relay and took it apart. After 40+ years the connector tab on the main contact was caroded. I wire brushed the connector tab and end of the contact shaft (on the bottom of the relay base and soldered them for a solid contact. They also also have a wire resistor that sticks inside the AC box that can be bad as well. However I have had and seen more relays bad than anything else.

Mark Smith

Canada Rocket

Thank for the advise gentlemen. Mark where would the fan relay be located?

spjrr

My car has ac and it is located on the top of the ac box under the hood.

Mark Smith

Canada Rocket

My car doesn't have ac. Under the hood all that I have is a resistor (similar to a condenser on a point ignition), then this wire goes to the wiring harness.

Peterbuilt

72 w no a/c doesn't have a relay.
http://willcoxcorvette.com/popup_image.php?pID=27586

spjrr

Rocket, sorry, don't know where the relay is on a non ac car. The response from pete above has a link to the circuit diagram at wilcox. It doesn't show a relay. So from that I assume non air cars don't have a relay. However, when I searched for the part I found this

http://www.partsgeek.com/tz88qn6-che...er+Motor+Relay

I did remove my switch and did same thing as with relay. Took it apart and cleaned the contacts. The wilcox diagram doesn't break down what speeds are to what output wires. But you can still check to see if any of those wires are passing any power with a simple test light. It also has a note that high is direct to the blower motor and doesn't go through the resistor. So based on that does your blower work on High?? if so the resistor is probably bad for the lower speeds. If it doesn't work at any speed then the switch has a problem. You should have power to one of the output contacts if you put the switch in any position other than off since as you said you have power to the brown lead on the switch.

Mark Smith

spjrr

Based on Petes last reply, I would suspect the switch or connections to its output leads. Thanks Pete, learned something new today.

Mark Smith

Canada Rocket

Thanks guys. The fan does not work at any speed. I will try and run a wire from the brown (live wire) to the output leads. If that works then I know it has to be the switch. BTW this forum is awesome. Your help is very much appreciated.