Blower Motor Blows On High Like Switch is on Low

[78RWDBigTen]

Blower motor runs right on low m1, m2, but only runs on Low, when switch setting is on high... I have replaced switch, resistor, relay, and motor. Test shows 3 volts on low switch setting, 6 volts on M1, 8 volts on M2, and 12 volts on high at the motor. Have cleaned the ground on motor.... not sure what way to go next?
Thanks

 

[WP29P4A]

When I trouble shoot this type of issue, I use a long test lead to "add" power to different locations in the circuit, to locate the problem. If you run a wire from the pos battery terminal to the positive terminal on the blower motor, and it works on high, you have verified that the blower is not the problem. If you are able to get the high setting by bypassing the switch, the problem probably has something to do with the switch.

You can use this method to locate bad grounds also, attach wire to negative battery terminal, then touch the other end to the ground on the circuit you are having problems with, if stuff starts working you have verified a bad ground.

 

[78RWDBigTen]

Thank you! I will go try the long test lead.

 

[WP29P4A]

Thank you! I will go try the long test lead.

Alligator clips on each end are helpful but not necessary.

 

[78RWDBigTen]

I ran a wire from the battery straight to the blower motor and it works on High.... Blower is not the problem.. I will look at the switch tomorrow to see if it is the issue.
Thanks again!!

 

[SirRobyn0]

I ran a wire from the battery straight to the blower motor and it works on High.... Blower is not the problem.. I will look at the switch tomorrow to see if it is the issue.
Thanks again!!

Do not overlook the high speed relay for the blower motor. If that is not functioning properly that could cause your issue.