Heater fan won't work
Thread Starter
4th Gear
Joined: Feb 2014
Posts: 4
Likes: 0
From: Thunder Bay Ontario
Heater fan won't work
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!
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!
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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From: Andover Mn
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
Mark Smith
Le Mans Master
Joined: Aug 2006
Posts: 7,426
Likes: 1,559
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Advanced
Joined: Nov 2012
Posts: 91
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From: Andover Mn
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
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
Last edited by spjrr; Feb 21, 2014 at 08:58 PM.
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Thread Starter
4th Gear
Joined: Feb 2014
Posts: 4
Likes: 0
From: Thunder Bay Ontario
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.