Heater Blower Motor Resistor
See attached picture. It appears someone changed the resistor to a Volvo resistor and rewired it. My blower motor is seized, so I can't see if it's working properly, but do the values look like this was a safe fix for the 944?
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chrischrischris
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Good question. I don't know if the values are in the electrical diagram for the car or maybe they are printed on the resistor itself. I can check my 84 later this week to see. As for the blower motor, I had good luck with one for a VW van.
I've got a local guy who rebuilds electric motors, so I'll see if this is in his wheelhouse or not. If not, I potentially have another source. Thanks for the info with the VW Van motor. Do you buy chance know a part number for it?chrischrischris wrote: Thu Aug 27, 2026 3:55 pm Good question. I don't know if the values are in the electrical diagram for the car or maybe they are printed on the resistor itself. I can check my 84 later this week to see. As for the blower motor, I had good luck with one for a VW van.
I think there is some risk. The resistance values are lower than what I found on an image of the correct resistor. Specifically, on speed setting 1 with the Volvo resistor, the resistance will be the sum of the 0.21 and 0.7 ohms = 0.91 ohms. The factory resistance on speed setting 2 is 0.9 ohms, basically the same. This means that the same amount of current is flowing in your car on setting 1 as would be flowing at setting 2 with the correct resistor. Porsche chose to use 2.5 mm2 wire for speed setting 2 to support that current, but used 1.5 mm2 wire for setting 1, as less current would be flowing. This is coming through the brown with yellow stripe wire of the harness. This wire may overheat, especially if the fan motor is stalled.
If it were my car, I would replace it with the correct resistor.
If it were my car, I would replace it with the correct resistor.
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chrischrischris
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Thanks for the information. Are the correct resistors readily available? Looks like mine has been run in the car for a while, but doesn't mean it's correct as you mentioned, plus it's easy enough to change it back. Thanks for the info.944er wrote: Fri Aug 28, 2026 4:43 am I think there is some risk. The resistance values are lower than what I found on an image of the correct resistor. Specifically, on speed setting 1 with the Volvo resistor, the resistance will be the sum of the 0.21 and 0.7 ohms = 0.91 ohms. The factory resistance on speed setting 2 is 0.9 ohms, basically the same. This means that the same amount of current is flowing in your car on setting 1 as would be flowing at setting 2 with the correct resistor. Porsche chose to use 2.5 mm2 wire for speed setting 2 to support that current, but used 1.5 mm2 wire for setting 1, as less current would be flowing. This is coming through the brown with yellow stripe wire of the harness. This wire may overheat, especially if the fan motor is stalled.
If it were my car, I would replace it with the correct resistor.
944 Fan Resistor.jpg
You probably will have to pick up a used one.eccs19 wrote: Sat Aug 29, 2026 8:03 am
Thanks for the information. Are the correct resistors readily available? Looks like mine has been run in the car for a while, but doesn't mean it's correct as you mentioned, plus it's easy enough to change it back. Thanks for the info.
My replacement motor arrived today. Fit in and seems to work fine. Question for someone with the same car. With it installed, even with the dial all the way to the left, fan still runs, just very slow. Is this normal or should it not run at all. The speed does get faster as I turn the dial, but just expected there to be a position with the fan not running. I wonder what if someone wired the resistor wrong when they switched it up.
Thanks. I was searching and kept getting different answers. I trust what you’ve mentioned just based on your knowledge I’ve seen online.944er wrote: Mon Aug 31, 2026 3:00 pm Normal. Fresh air ventilation for safety. Prevents exhaust buildup if there is a leak in the exhaust and body somewhere.