Unknown Fuse box and Unknown resistor - PeachParts Mercedes-Benz Forum

Chadahar · #1 09-13-2008, 04:13 PM

Following is a picture of a fuse box next to the primary fuse box in my 1989 560 SEC.
Anyone know what this fuse box controls? The lower fuse was missing this morning when I looked at it trying to find why my radio was blowing it's fuse.

Should these fuses be blue?

Then I found this resistor that was smelling of burning and I think it has something to do with the radio circuitry. The arrow points to the radio fuse. The only thing on was the radio for a short period of time and then the fuse blew, tried it again several time with the same result. Also the Antennae will only go up part way. I did try the radio with the Antennae unplugged to see if it was the antennae that was causing the fuse to blow. It wasn't.
I believe the bad resistor(I didn't get the number off it though) is the culprit.
Radio is good and I have the code and it played for a few minutes before the fuse blew the first time. Afterward the fuse blew immediately.
Yes, the fuses will all be changed out to copper ones shortly.

stevebfl · #2 09-13-2008, 04:30 PM

Fuses? Maybe seat heaters. If they are seat heaters then 25 amp blue is probably OK.

Grey plug in is a diode invoved with powering seat adjustment with door open. Pull it and the key will have to be on for the seats to adjust.

Chadahar · #3 09-13-2008, 04:44 PM

Could be? Do they both have to be in for both seats to heat?? Neither did , but I haven't tried them since I replaced the fuse. Also I have this mysterious bundle of wires that have been cut under the drivers seat and I was thinking that it was for the Car Phone that was in the car originally, but I don't know for sure. Everything works but the seat heaters. The phone was gone before I got the car. Was maybe the seat heater relay under the driver's seat? Seats do all their motions so whatever that bundle is, it doesn't affect anything else in the car that I'm aware of.

I'm thinking that Diode is bad, but will have to check the car and see if the seats switches work with the key off. I don't think they do, but I could be mistaken.

stevebfl · #4 09-13-2008, 05:02 PM

For the seats to work with the key off the door must be open. That is when the diode plays its part.

tinypanzer · #5 09-19-2008, 06:00 PM

If the resistor you mentioned is part of the radio circuit (I have no idea why it would be) and it is going bad, it could create a condition that would cause too much current draw, but I'm not convinced that resistor is part of the radio circuit. I don't really know enough about that car.

Pop it out and measure it with a meter to see if its value has changed from what it is supposed to be. Also look for signs of shorting or arcing. Even if its not the culprit, a resistor that is starting to burn up is a real hazard. They can catch fire or melt things nearby.

If the resistor is burning up, it would be wise to make sure that the resistor burned up because it failed, rather than the circuit it's in drawing too much current. Otherwise, the problem will come back.

Another possibility is the radio has a blown transistor which overloads the circuit.

J.

J.

tinypanzer · #6 09-19-2008, 06:04 PM

Oh, by the way, checking a diode is easy.

Use a multimeter set to the ohms setting. You should have little resistance with the leads connected in the correct polarity, and infinite resistance with them connected with opposite polarity to the diode. Depending on the circuit, you may have to lift one leg of the diode out of the circuit to get an accurate test since other components may allow current to pass through, obfuscating your results. If the diode passes current in both directions, it's shorted. If it doesn't pass current in either direction, it's blown open.

J.