I am troubleshooting a rear wiper motor problem in a 2003 Ford Focus wagon (LE).

When I measure the voltage to the contacts (with the wiper switch on), i get intermittent (~4 s) voltage at 200 mV. This indicates to me that the relay is working.

However, when I plug in the brand new wiper motor it will engage for 2s, and then blow a fuse. I replace the fuse and it does the same thing. The motor says it's a 12V motor on the casing. This indicates to me that it's not receiving enough voltage, which is causing an amperage spike.

Question: Why would only 200 mV be being sent back to the wiper motor? Is this typical? Is there a transformer in the actual motor assembly that jumps it up to 12V that is malfunctioning?

If this were the case, however, it wouldn't do so on a brand new wiper motor.

Thanks, Scott

  • Does it blow the fuse when the wiper motor is switched of as well or only when engaged? Have you checked to see if it is grounding out somewhere?
    – Seminecis
    Sep 7 '13 at 17:20
  • No, the fuse does not blow when the motor is switched off, only once it is engaged. How do I check to see if it is grounding out? Thanks.
    – svh160
    Sep 8 '13 at 19:07

Where exactly are you measuring the voltage and getting 200mV?

If you're seeing this at the connection for the wiper motor, then I strongly suspect your problem is upstream of the wiper motor. You need to get enough power (volts * amps) to the motor to run the wipers. Even if there were a DC-DC step-up converter in the motor (exceedingly unlikely), you can't create power out of thin air, so that 200mV that you measured would need to be capable of delivering a seriously high amount of current. It just doesn't make sense to design things that way IMO.

  • This answer has led me to the conclusion that I need to do some more troubleshooting upstream of the motor.
    – svh160
    Feb 26 '14 at 17:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.