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How can I test a DC car blower motor with an external resistor? (note that there is an existing question about testing DC motors, but the assumption there is that it has an internal resistor, and it also assumes the tester has access to a "good" motor or a schematic, which I do not)

The motor has two terminals on it and the associated resistor has 4 different labeled resistance levels: R8K, R40K, R50K, and R70K.

Is testing the motor as simple as hooking a car battery to a high wattage 8000 Ohm resistor and then connecting the leads to the two spade terminals on the motor, or is it more complex than that?

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To test that, I would use a fused supply from a battery to each of the terminals on the resistor (which will feed one of the terminal so n the motor, a ground connected to the other) and check for the different speeds.

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The resistances are nothing like 8K ohms, more like a few ohms- enough current has to get through there to run a blower!

Check the service manual for the correct resistance values. Full speed is probably just the motor across 12 V with no series reisistor, but again, check the schematics in your service manual.

This is not the appropriate forum for car repair questions - there is a motor vehicle SE, but you can also check this Pelican link, I have found them reliable for other cars.

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  • \$\begingroup\$ Why does the blower have an 8K external resistor then? I have no service manual (I said that in the question). \$\endgroup\$ – Tyler Durden Feb 3 at 14:17
  • \$\begingroup\$ What makes you think it has an 8K resistor? You didn’t measure it, did you? K could refer to tolerance, for example. \$\endgroup\$ – Spehro Pefhany Feb 3 at 14:19
  • \$\begingroup\$ Looks more like .4/.5/.7/1.8 ohms to me from the markings but again I would suggest getting ahold of the manual. \$\endgroup\$ – Spehro Pefhany Feb 3 at 14:24

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