help with 300SD electrical question - PeachParts Mercedes-Benz Forum

greendream · #1 07-03-2008, 02:18 PM

Hello and thanks for past advice.
I just installed my new "unwired" AC servo replacement and am now chasing electrical and vacumn issues. What is the most likely candidate for an intermittent blower motor. It worked fine for a while on defrost. Then it quit and came back on once. Now nothing. I have my multitester, vacumn guage and corresponding manual pages. Any advice on the most likely candidates before I get started?

TX76513 · #2 07-03-2008, 02:29 PM

The most likely or common problem is your ignition switch. Next time it quits lightly wiggle your key left to right. If blower comes on there is where your issue is.

greendream · #3 07-03-2008, 02:44 PM

Quote:

Originally Posted by TX76513

The most likely or common problem is your ignition switch. Next time it quits lightly wiggle your key left to right. If blower comes on there is where your issue is.

thanks. tried that. can't get it to come on.
This is my first foray into electrical diagnosis so forgive the following ignorant questions: Am I measuring AC, DC, volts, amps? What should I set my tester on? Where do I place the probes?

LilTimmy · #4 07-03-2008, 05:43 PM

Start the car and turn the defroster on. If the blower doesn't kick on then try smacking it with your hand. Its under the dash on the passenger side. Sounds to me like you have bad brushes on the blower motor. I had the same problem a few months back. Though I hate doing business with them, ************** selld a brush replacement kit with instructions for fairly cheap.

greendream · #5 07-05-2008, 01:24 PM

Quote:

Originally Posted by LilTimmy

Start the car and turn the defroster on. If the blower doesn't kick on then try smacking it with your hand. Its under the dash on the passenger side. Sounds to me like you have bad brushes on the blower motor. I had the same problem a few months back. Though I hate doing business with them, ************** selld a brush replacement kit with instructions for fairly cheap.

This sounds like a possibility or perhaps some other loose or worn connection. My kid slammed the door today and it suddenly come on.

Palangi · #6 07-05-2008, 07:43 PM

It sounds like the brushes in the blower motor are worn out. There is a DIY article on this job, however, if you're not comfortable with soldering, you might need to enlist some help.