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Old 11-07-2010, 09:19 PM   #1
garnita
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Join Date: Nov 2010
Location: Edmonton
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88 B350 need help troublshooting heater problem

My heater blower motor quit working so I tested the motor directly hooked to the battery and it works.

Now, something strange is happening when I check the voltage in the wiring coming to the motor. For example, it will read @ 12 volts, then I plug the wiring harness in (it has 2 wires - live and ground) hoping the motor with run, I get nothing. When I unplug the harness, and test the voltage again, it is now down to only a couple volts.

If I shut the key off and then turn it on again and recheck voltage, sometimes it registers @ 12 volts, but I've seen anything from 2 - 8 volts (i.e all over the map). My switch is good, but not sure about the resistor assembly or the blower motor relay. Please help me to troubleshoot this! I know where the resistor assembly is, but not sure about the relay.

thanks,
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