The heater switch in my son's 69 Chevelle only work on the low setting,
I need to know how to check the switch and heated resistor.
Also I am not sure where the resistor is located at.
Thanks

I'm not sure of the location. It seems to change whether you have A/C or not, 6 cyl or V8, and maybe even other factors.

Regardless, the resistor is usually mounted into a recess with a three prong plug.

The picture I'm looking at in my '68 assembly manual shows light blue, dark blue, and yellow 16 gauge wires going to the plug. Of course, there's also a relay involved.

I think '69 is the same, but I'm not sure.

To see if you're getting low and medium power check for voltage on the yellow when the switch is in the low speed position. Check for voltage on the light blue in medium.

For high there's an 18 ga orange wire going from the switch to the relay. The relay should be mounted on the firewall somewhere with a three prong plug that has a 12 ga orange, a 12 ga purple, and a 16 ga light blue.

The light blue goes directly from the relay to the resistor. The orange goes to the battery source on the horn relay (with an inline fuse somewhere along the line). And the purple goes directly to the blower motor to power it up.

You'll also see a 12 ga blue wire on the relay going to the blower, but it's not part of the plug. And there's an 18 ga orange wire going from the fan switch to this relay as well. This is your high speed wire.

Shoot me an e-mail and I'll try to help if you can get back to me while I'm still in town.

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Chad Landry
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ACES Member #04556
'68 El Camino