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78 MGB Heater Fan Resistor???

Moss Motors
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hanker Silver Member Hank R
Denver, CO, USA   USA
Hello, I've got a 78 B equipped with factory/dealer installed A/C. I'm trying to make my 2-speed heater fan motor work. I,ve replaced a bad rocker switch on the dash and now have power to the connector on the firewall but the fan motor still doesn,t run. The wires from the firewall connector go into the heater box and a single wire comes out and connects to the fan motor. None of my schematics show a resistor in the heater circuit. Moss Motors does not have a heater resistor in their catalog either.

My question is what do those wires going into the heater box connect to? If they do go to a resistor can I access it by removing the fan motor?

Thanks in advance for any input.

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garage 312.jpg    39.8 KB
garage 312.jpg

29desoto Avatar
29desoto Gold Member Wayne Sanders
Outside Otis, OR - in the woods!, USA   USA
1965 MG MGB V6 Conversion "Carmine"
1968 MG MGB GT "New Yeller"
1973 MG MGB GT "Eliza - FIRST PLACE - MG2013"
1984 Chevrolet Corvette "The Green Weenie"    & more
Yup, resistors are at the top of the heater box on the inside, right about where your index finger is.

Be sure to check that sneaky little ground wire below you there.

And you do know the power cable to the motor is unplugged, right? eye rolling smiley

(Dang, it! Another dangling participle! How do I do that?)



Wayne Sanders
Rose Lodge, OR
(TD 4288)

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

73 MGB-GT virtually stole this one. Someone up there likes me.

68 MGB-GT the daily mule. Solid as a rock, but rattles like a can full of them!

79/65 MGB - Carmine- V-6 - T-5
This car is now very nearly completely done. Sure to find something else, but not now.........



Edited 1 time(s). Last edit at 2012-12-19 12:49 AM by 29desoto.

rundjk Avatar
rundjk David Kinsey
Virginia Beach, USA   USA
1980 MG MGB "Runaway"
And, the resistor, IMHO, can be eliminated as it only makes a slow fan slower. Check Limey's page (Bits 4 Brits) and Advance Auto Wire and get yourself a relay for that circuit so you get all the power you can going directly to the motor.



David J. Kinsey
Virginia Beach
Tidewater MG Classics
1980 MGB "Runaway"

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hanker Silver Member Hank R
Denver, CO, USA   USA
Fellas, Thanks for the info. I'll take a look at the resistor and decide whether to use it or by-pass it.
Thanks Wayne, The connector in the photo is unplugged for diagnostic purposes.

jborkman Avatar
jborkman Jim Borkman
Clarence, USA   USA
My question is where do these wires terminate outside of the heater box?

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