I keep on blowing the same fuse! - PeachParts Mercedes-Benz Forum

zeronero · #1 01-04-2005, 06:32 PM

It started yesterday, on the freeway, all of a sudden my stereo just losses power. It was to late to start to work on it so today I put a new fuse in and it blew again, I tried this two or three times.

The fuse blows right when I turn the ingnition to the accessory position. It's the #1 fuse that keeps on blowing which powers the radio, cigar lighter, rear defroster, glove box light, folder rear headrests, and the rear compartment.

I think that maybe some wires somehow got crossed behind the radio but don't want to pull it out if I don't have to. It is an aftermarket unit that I installed myself around 2 years ago. I'm just wondering if anything else related to this fuse would do the same thing.

190edude · #2 01-04-2005, 08:45 PM

Definately shorted somewhere on that circuit.

zeronero · #3 01-05-2005, 05:41 PM

I took out the stereo and capped all the power wires dealing with the stereo and the fuse still blows, so I doubt that it has to deal with the stereo but I have no other place to look. Everything else dealing with that fuse has not been touched and I don't see how those other devices would blow it anyway. I really don't know what it could be, I was fairly sure it was the stereo but now I can't say for sure. I want to get this fixed before I drive to Vegas or I'll go crazy!

I NEED HELP!

jhal · #4 01-05-2005, 06:00 PM

I had that happen once and it turned out that a coin (dime)had fallen into the lighter socket after removing my phone charger from it. The coin obviously shorted the socket and blew the fuse. Just food for thought....

pentoman · #5 01-05-2005, 06:23 PM

I guess you could test all your live wires to see if there is a current flow between them and earth. Try it with your stereo wire, as you have ruled out the stereo but not necessarily the wiring.

good luck

Russ

theairboy · #6 01-06-2005, 01:48 AM

look on the fuse box cover and see what some of the other idems are on that fuse.

If i was doing it I would unplug the power antana at the motor then see if the fuse blows. If that wasnt it then start unpluging things on that curcut until they are all unpluged. If that Didnt do it then check wires for shorts or ground faults.

mpolli · #7 01-06-2005, 01:38 PM

Hold the blown fuse up to light and see if the element has a small crack in it or it is blown up with metal splattered on the insed of the fuse body. This will give you an idea if you have a dead short or more of an overload. Also, if it lives for a second or a few seconds then it is probably not a dead short. In any case, the advice from theairboy is correct.

Mike

zeronero · #8 01-11-2005, 03:02 AM

Thanks for the replies!

I finally found the problem, a wire that goes to the cigarette lighter had a short in it and was burnt down to the bare wire. The wire that had the problem was a split from a harness that went from the cigarette lighter to some connection that went to nothing, so I don't know how the short started. I ended up just cutting it.

In order to find it I put a 25 amp fuse in the box, instead of the 16 amp it needs. Once that was in, after about 5 seconds I saw smoke and located it. I had to take out the whole center console to get to the wire since it was very deep inside the dash.

So now everything works and is back to normal. So far that cut wire has not affected anything.

fz500sel · #9 01-11-2005, 08:49 AM

I'm glad you found out the problem. That really isnt the best method of troubleshooting though. By the time you finally "see the smoke", there is no telling what other damage you can cause. The cars nowadays have too many sensitive electronics to take the chance.

Electrical problems or as some people call them "gremlins" can be the hardest problems to diagnose.

I work at Home Depot in the electrical department and I cant tell you how many people come into the store and want to just keep increasing the amperage of their circuit breaker or fuse, just so that they no longer blow the fuse or CB. They dont realize that they are literally playing with fire. If you listened to some of these customers, it would scare you to think that they were working on electrical in their houses.

The best way to troubleshoot the problem is to isolate the short. Start by eliminating the load until the fuse no longer blows. Then you know that your problem lies within that circuit that the load is on. From that point it is a matter of eliminating which part of the circuit is causing the problem. Most of the circuits on our MB's have many different things that they control. You can see the list of the items via the fuse cover. It lists all of the things that each fuse protects.

A good multimeter will help. You can "ring" (check for continuity) each wire to ground and see if you have a short.

zeronero · #10 01-11-2005, 02:16 PM

Quote:

Originally Posted by fz500sel

That really isnt the best method of troubleshooting though.

For Sure.

I had a strong feeling that the problem was in that area so that's why I used that method. It would have taken forever to try to isolate the cause since the fuse had so many things running off it going to many different areas of the car.

stevenstevensteven · #11 09-14-2007, 11:08 PM

Very interesting thread. I have a similar issue.

When I plug-in my cell phone charger, or any other DC device, into the cigarette lighter, my radio shuts off and so does power to the cigarette lighter. However, my fuse does not blow, even though I have installed the correct amperage fuse. When I disconnect the cell phone charger from the cigarette lighter, power is restored to the radio typically after I turn-off, then turn-on the car.

This started about a year ago, with no apparent reason. The radio was installed about 4-years ago.

So, I replaced the old cigarette lighter with a new one, as the previous owner was a smoker. So now, I have a new lighter installed. But unfortunately, this did not impact the problem.

Any ideas?

zeronero · #12 09-17-2007, 03:33 PM

My car currently still has this problem, still have no clue what it could be. As far as the electrics in the car go, there are various issues like this that are just part of the car, something that I don't see ever getting fixed, just have to deal with them.