Need help wiring Thrift air heater in 65 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**bigmoe** · 12-03-2019, 05:04 PM

So my project is a 65 Gmc. Bought it as a basket case. Right now I'm knee deep in wiring using a Speedway Motors 22 circuit universal kit. I'm pleased with the kit. It comes with lots of diagrams. Various wires are grouped appropriately and wires labelled. Came with a light switch. Column wires plugged right into my aftermarket steering column so nothing to figure there.
One thing I've done is toss the Deluxe heater that sits in the engine bay (ugly and in the way) in favor of an original Thrift Air unit that mounts inside. I bought a repop Thrift Air dash switch/cable pull to operate it. I dug out the box of original cab wiring to compare. The new switch has 5 connections compared to 4 on the original. Both switches have some markings on back. I made a crude drawing to compare the two. Any input on how to wire this switch would be appreciated.

*gmachinz* · 12-04-2019, 09:12 AM

Brown on your OE switch was fused power coming to it-and since there is no resistor in your diagram I assume the switch itself has an internal resistor set of coils to vary fan motor speed?
If so, then you’ll need to which terminal on the new switch is a constant power coming in, then I’d use a jumper and bench test running a grounded blower motor to see which terminals create a low, medium and high then label and wire accordingly.

**bigmoe** · 12-04-2019, 10:19 AM

Yes there's a resistor on the back of the heater box. The box has it's wiring intact. You confirmed what I thought that the brown wire is the + feed. On the two switches 3 out of 4 are labelled the same. I'm going to assume M and C are the same? And I'm not sure what the 5th unlabelled pin on the new switch would be for?. Ground? I'll leave it unhooked for now. The heater box is self grounding through the mounting bolts but I added a ground wire from the box to the body just for good measure. I think I know enough to bench test it as you suggest.

**bigmoe** · 12-04-2019, 02:30 PM

Well I got it. "C" and "M" are the same. Left that fifth connection alone. Hooked up 12v to try it and it works!. The switch has off and three positions but the fan only has low and high. Chances are I'll never use the heater but in order to pass gov't safety inspection I need a working defrost.

12-03-2019, 05:04 PM	#1
bigmoe Senior Member Join Date: Oct 2014 Location: Brandon, Manitoba, Canada Posts: 953	Need help wiring Thrift air heater in 65 So my project is a 65 Gmc. Bought it as a basket case. Right now I'm knee deep in wiring using a Speedway Motors 22 circuit universal kit. I'm pleased with the kit. It comes with lots of diagrams. Various wires are grouped appropriately and wires labelled. Came with a light switch. Column wires plugged right into my aftermarket steering column so nothing to figure there. One thing I've done is toss the Deluxe heater that sits in the engine bay (ugly and in the way) in favor of an original Thrift Air unit that mounts inside. I bought a repop Thrift Air dash switch/cable pull to operate it. I dug out the box of original cab wiring to compare. The new switch has 5 connections compared to 4 on the original. Both switches have some markings on back. I made a crude drawing to compare the two. Any input on how to wire this switch would be appreciated. Attached Images

12-04-2019, 09:12 AM	#2
gmachinz Account Suspended Join Date: Jun 2011 Location: Des Moines, IA. Posts: 4,143	Re: Need help wiring Thrift air heater in 65 Brown on your OE switch was fused power coming to it-and since there is no resistor in your diagram I assume the switch itself has an internal resistor set of coils to vary fan motor speed? If so, then you’ll need to which terminal on the new switch is a constant power coming in, then I’d use a jumper and bench test running a grounded blower motor to see which terminals create a low, medium and high then label and wire accordingly.

12-04-2019, 10:19 AM	#3
bigmoe Senior Member Join Date: Oct 2014 Location: Brandon, Manitoba, Canada Posts: 953	Re: Need help wiring Thrift air heater in 65 Yes there's a resistor on the back of the heater box. The box has it's wiring intact. You confirmed what I thought that the brown wire is the + feed. On the two switches 3 out of 4 are labelled the same. I'm going to assume M and C are the same? And I'm not sure what the 5th unlabelled pin on the new switch would be for?. Ground? I'll leave it unhooked for now. The heater box is self grounding through the mounting bolts but I added a ground wire from the box to the body just for good measure. I think I know enough to bench test it as you suggest.

12-04-2019, 02:30 PM	#4
bigmoe Senior Member Join Date: Oct 2014 Location: Brandon, Manitoba, Canada Posts: 953	Re: Need help wiring Thrift air heater in 65 Well I got it. "C" and "M" are the same. Left that fifth connection alone. Hooked up 12v to try it and it works!. The switch has off and three positions but the fan only has low and high. Chances are I'll never use the heater but in order to pass gov't safety inspection I need a working defrost.



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