My 2001 BMW 325CI windshield washer pump failed. While diagnosing the problem I discovered that with ignition off I have a constant 8 volts on the lead to the pump. With the ignition on and the windshield wiper handle in the wash position I get the expected 12 volts. Is the constant 8 volt reading in normal or is that what caused the pump to fail?
The reading you saw very well could be a normal condition. It just depends on how the circuit is designed that controls the pump motor. What limited data I could see for your vehicle it looks like there is a control module for the pump. If you are still suspecting trouble you could check the current flow through the motor. If there is more than a few milliamps of current flowing while the ignition is off then the control module may be bad. Before checking the current see if you can just disconnect the wiring to the motor and then check the voltage. If the voltage stays close to the 8 volts then I would say there isn’t a problem with the controller.
No matter what voltage reading you are getting you must also ask yourself the questions.Is the pump running continusly? is the motor hot? is my battery dying? if you answer no it is safe to go on.
I disconnected the wiring to the pump checked the voltage on the wiring and it a constant 8 volts. I don’t have a meter to check for milliamps. The motor does not run at all, but it does get hot when 12 volts are applied. The battery seems to be good.
I think I will get a new pump, install it, and see how things go. Thanks for the advice.
Well since you removed the motor connection and the voltage didn’t change that means the motor connection had no effect on the circuit. Changing the pump motor should fix you up. You might see if you can find a broken connection between the connector and motor brushes. If you can find the break and repair it, you may not need to purchase a new motor.
Edit: I missed your comment about the motor getting hot when connected to power. I should have read it closer. Since the motor gets hot when connected to power that means the armature of the motor is stuck or jammed somehow. If you can free up the movement that should fix the motor if it hasn’t been too damaged by heat.
I already bought and installed the new motor and it works great. The old motor seems to be sealed so I cannot take it apart without breaking the casing.
I really appreciate your input.
You’re welcome for the help and thanks for the feedback. Glad you got it fixed.