Author Topic: Heater Blower Resistor Location  (Read 194 times)

gcw206

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Heater Blower Resistor Location
« on: February 13, 2020, 20:15:33 »
My heater blower in my 1969 280SE Coupe W111 will not work.  The fuse is good, and I am trying to locate the series resistor, but am having no luck.  Where is it located, and how do I test it?

Aaron h

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Re: Heater Blower Resistor Location
« Reply #1 on: February 14, 2020, 01:54:23 »
In a W111/W112 coupe`/cabriolet the heater fan switch is the actual resistor.  There is no remotely mounted resistor.  Remove the phenolic plug from the front of the heater case and test for continuity or excessive resistance across the motor itself.  At the same time, also test the plug itself to insure that the blower switch is supplying 12V+ in the "hi" position (all the way to the right, last detent), and that the voltage varies when the knob is turned counterclockwise.  And last, confirm continuity of the ground for the circuit. 

Theses switches rarely go bad.  The blower motor itself is what usually quits working having seized up. 
1966 250se coupe` black/dark olive/Macassar Ebony
1966 250se black/dark olive leather
1970 600 Midnight blue/parchment/Macassar
1972 280sel black/black leather
1971 300sel 6.3Papyrus white/dark redleather/Macassar
1973 300sel 4.5 grey blue met/blue leather/walnut
1986 635csi, M-sport, Cosmos blue

gcw206

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Re: Heater Blower Resistor Location
« Reply #2 on: February 14, 2020, 14:24:09 »
Thanks, that answers my question.

Aaron h

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Re: Heater Blower Resistor Location
« Reply #3 on: February 14, 2020, 20:44:54 »
You're welcome!  Do let us know of your progress and what you find so others reading can benefit from the completion of your adventure.  I, myself, will be curious a to what problem(s) you find. 
1966 250se coupe` black/dark olive/Macassar Ebony
1966 250se black/dark olive leather
1970 600 Midnight blue/parchment/Macassar
1972 280sel black/black leather
1971 300sel 6.3Papyrus white/dark redleather/Macassar
1973 300sel 4.5 grey blue met/blue leather/walnut
1986 635csi, M-sport, Cosmos blue

gcw206

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Re: Heater Blower Resistor Location
« Reply #4 on: February 14, 2020, 22:50:09 »
Hello,
You were 100% correct; the fan blower motor was/is dead. Is there an easy way to replace just the motor w/o full blown open heart surgery? 
I don't want to remove the entire plenum if at all possible, just r/r the motor.
Thanks agin for your input,
Galen

Aaron h

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Re: Heater Blower Resistor Location
« Reply #5 on: February 15, 2020, 14:27:47 »
No, unfortunately there is no other way to replace the motor without having to remove the whole heater box from the car.  It's not a particularly difficult job on a W111/W112 coupe`/cabriolet.  It's more time consuming than anything.  Just take advantage of the heater box being out to renew the heater hoses, grommets through the firewall, and having both heater cores cleaned out internally.  You'd be amazed at how much dirt and silt settles in the bottoms of the heater cores impeding coolant flow. 

The blower motor is no longer available new, but for ease of your searching the part number is 000-835-09-02, and the same blower motor is used on all W111/W112 coupe` and cabriolet, W111/W112 sedans, as well as all W110 cars.  I recommend searching for this blower motor under the W110 because anyone selling a blower motor for a W111/W112 coupe`/cabriolet will likely charge more ONLY because it came from a W111/W112 coupe`/cabriolet.  99% of people don't know that this blower motor was used in many other models. 
1966 250se coupe` black/dark olive/Macassar Ebony
1966 250se black/dark olive leather
1970 600 Midnight blue/parchment/Macassar
1972 280sel black/black leather
1971 300sel 6.3Papyrus white/dark redleather/Macassar
1973 300sel 4.5 grey blue met/blue leather/walnut
1986 635csi, M-sport, Cosmos blue