Blower Motor Problems 300E
 

The blower motor was dead. I removed from the car and oiled it hoping it would move more freely by hand. Connected to 12 volt battery source, and it ran at high speed. I hooked up to the blower leads on the car and got high speed fan performance when high speed fan was selected but nothing on low speed although there was voltage present.
The three pin connector on the firewall showed all to be well:
At low speed, the control voltage was a little better than 1V. With the blower on high speed, the control voltage was approx 9V.

- I checked the voltage on the blue and red wires that go into the blower motor and it reads approx 12 volts regardless of whether the ac/heater selected on/off.

My guess is that the blower needs to be replaced. Is there something that I have neglected to check?

Walter
1990 300 E

check the commutator and brushes on the blower.any breaks or dark spots on the commutater mean its worn out.if the brushes are too short they can be replaced:)

I have had blower motor problems myself with my 300E, I replaced the regulator underneath the blower motor mounting bracket. Mine works good now.