Delray_58
Frequent Contributor
Posts: 1063
Loc: Scotts Valley, CA
Reg: 03-20-10
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01-20-25 06:50 PM - Post#2877275
I'm installing an NOS Heater fan switch as part of my Deluxe Heater upgrade. I tested the NOS switch and after cleaning the contacts with electrical contact cleaner, the switch works reliably. However, when bench testing it I found that the resistance coils get really hot. In fact, they glow a dull red. I checked the temperature of the coils using an infrared thermometer and they are around 400F. Fortunately, the ceramic shields are significantly cooler at about 150F.
Understanding the theory of operations, I expected the coils to get hot, buy 400F seems like a lot, as well as glowing coils.
Has anyone else tested or seen this on a 58 Heater Fan Switch before? Thoughts?
Here are links to photos:
https://drive.google.com/file/d/1D8eNUA_abaI67 Q8fL...
https://drive.google.com/file/d/1D7tuUVI4Pxc68 V10D...
Thanks!
'58 Delray 283 3-speed OD
In the family since new |
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JayChicago
"14th Year" Silver Supporting Member
Posts: 577

Loc: Chicago
Reg: 01-03-13
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01-24-25 11:05 AM - Post#2877351
In response to Delray_58
No one has replied so I'll give my two cents, even though I have no direct knowledge. (my car has VintageAir, original fan switch is non-functioning)
I agree with you, that very hot resister is probably normal, as designed. Other resisters like that I have experienced do indeed get dull-red hot. Hence the big ceramic protection around it.
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Delray_58
Frequent Contributor
Posts: 1063
Loc: Scotts Valley, CA
Reg: 03-20-10
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01-27-25 10:05 AM - Post#2877446
In response to JayChicago
Thanks so much! I did some measurements and calculations yesterday and determined that the the entire system consumes between 61 (low fan speed) and 64 watts (high fan speed). However, the resistor alone consumes 25 watts at low speed, 14 watts at medium speed, and 4 watts at high speed.
If you can imagine putting your hand on the surface of a 25 watt light bulb, it will be pretty hot. So, a hot power resistor consuming 25 watts doesn't seem out of the ordinary.
Also, I ran the recirculating heater that's currently installed on my car and checked the temperature of the resistor. It certainly gets hot, but I wasn't able to get a TC or IR temp reading becuase of difficult access. However, the resitor coils are closest to the factory radio steel case, which can amply withstand that radiant heat transfer.
So, my conclusion (and thanks to Jay for confirming) is that as long as I make sure there are no wires in contact with the coils or the ceramic sleeves, this is behaving normally.
I hope this post will help answer questions for future searches on this topic.
'58 Delray 283 3-speed OD
In the family since new |
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