83 300sd Brake Lights Blown Fuse help please - PeachParts Mercedes-Benz Forum

JamesDean · #1 03-15-2012, 10:29 PM

Quote:

Originally Posted by ShadeTree300SD

Yak, thanks for the info and the link. It will probably help out. I wanted to summarize where I stand so far with tests and observations:

I cannot get the fuse to blow applying the brake sitting in the driveway.
Just driving slow around the neighborhood the fuse won't blow.
Seems to only blow the fuse after being up to about 30 mph.
The fuse will blow with the combination switch disconnected.
Fuse will not blow with tailights disconnected.
A red fuse will blow also even though it's twice the size.

I disconnected the cruise control thing under the glove box but not the actuator. Where is the actuator located? I'm curious and suspecious about the warning system stuff because it doesn't seem like any of that stuff works at all.

Thanks again all for the input and help!! Very much appreciated!!!!!!

Thanks for the summary! That's very helpful.

The actuator is connected directly to the amplifier under the dash, so effectively its disconnected.

Try this, look in the driver's footwell. Remove the carpeted piece thats on the center console. There is a connector down there that connects backup tail lights and speedometer signal and a few other things. See if anything is a miss there.

On the 560SEL, that connector was taken apart and we had no speedometer or rear backup lights.. that was the culprit.

The only thing I can think of that change when you go from standing to 30+mph is the speedometer input signal. This signal is generated by a sensor on the tail of the transmission. I believe its an inductive pickup sensor for your car, hall-effect for newer. Perhaps it is grounding out somewhere.

You're clearly taking down more than 16A when it goes. Something is grounding out when it shouldn't be.

Another idea might be the warning relay, I believe its right next to the cruise control box.. I've read things can fail inside those and you lose the buzzer..

Finally, double check your tail light harnesses, just make sure they look clean and you dont see any wires touching each other. You should be able to connect your new meter to ground and the 12V wire on the harness and verify there is no continuity.

Just some ideas.

ShadeTree300SD · #2 03-15-2012, 10:36 PM

JamesDean, the warning relay is interesting because there's never any warning buzzer for anything. The sensor on the tranny is an interesting idea also. I'm looking forward to trying these ideas out!

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