1991 300E Fuse #9 Kept Blowing
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Senior Member
Joined: Feb 2007
Posts: 270
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From: Western Michigan
2003 E320 4Matic Wagon & 1997 E320
1991 300E Fuse #9 Kept Blowing
Fuse #9 blew on my 1991 300E. I tried to put a new fuse in there and it blew three more times. All this happened with the ignition off and doors closed. Somewhere there must be a short.
This is the 7.5 A fuse that is for the clock, radio, overhead light, sun visor light, and a few other things.
Any help and suggestion on how to proceed to check the faulty item? I understand that there might be hundreds of things that can cause this but any wisdom and experience are appreciated.
This is the 7.5 A fuse that is for the clock, radio, overhead light, sun visor light, and a few other things.
Any help and suggestion on how to proceed to check the faulty item? I understand that there might be hundreds of things that can cause this but any wisdom and experience are appreciated.
Member
Joined: Feb 2007
Posts: 117
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From: Northern Michigan
92 300TE 4Matic
Start with the wiring diagram:
Try the headlight trick:
Now start unplugging stuff til the light goes out.
Start with the easiest things to get at first.
A look at the wiring diagram above shows that most of the stuff is near the fuse.
I'd start by unplugging the convenience relay and power seat relay (in box next to fuse box).
Yank the warning buzzer switch (don't want it anyway)
Disconnect the sun visors.
Then it looks like they get harder to reach after that so hope its one you can reach.
Or pull the fuse box and see how many wires go to the fuse.
Yank 'em till the light goes out and then find evey thing that works, what's left are the suspects.
Try the headlight trick:
Use the headlight trick to get all the information you can about the problem.
Here's a picture of the trick in action on the fuse C circuit:
The headlight (must be a working headlight) acts like a 3-4 amp fuse but, instead of blowing, it lights up.
The circuit I was working on is powered all the time. So I just hooked one side to the battery. Fortunately Mercedes made the load side of the fuse holder the part that sticks up so you can clip onto it.
Here's a picture of the trick in action on the fuse C circuit:
The headlight (must be a working headlight) acts like a 3-4 amp fuse but, instead of blowing, it lights up.
The circuit I was working on is powered all the time. So I just hooked one side to the battery. Fortunately Mercedes made the load side of the fuse holder the part that sticks up so you can clip onto it.
Start with the easiest things to get at first.
A look at the wiring diagram above shows that most of the stuff is near the fuse.
I'd start by unplugging the convenience relay and power seat relay (in box next to fuse box).
Yank the warning buzzer switch (don't want it anyway)
Disconnect the sun visors.
Then it looks like they get harder to reach after that so hope its one you can reach.
Or pull the fuse box and see how many wires go to the fuse.
Yank 'em till the light goes out and then find evey thing that works, what's left are the suspects.
Thread Starter
Senior Member
Joined: Feb 2007
Posts: 270
Likes: 1
From: Western Michigan
2003 E320 4Matic Wagon & 1997 E320
Thanks, MediumKahuna, This is a good idea and I need to get some clips and wires to fabricate a light.
Now I think it is the driver side visor. My daughter broke the visor clip and I was trying to fix it yesterday. Maybe the twist of the visor shorted it.
In the diagram, fuse 9 was 10 A. Mine was 7.5 A (white color).
Also where are the visor lights plugged in? Is that a relay in the box behind the fuse box??
Now I think it is the driver side visor. My daughter broke the visor clip and I was trying to fix it yesterday. Maybe the twist of the visor shorted it.
In the diagram, fuse 9 was 10 A. Mine was 7.5 A (white color).
Also where are the visor lights plugged in? Is that a relay in the box behind the fuse box??
Member
Joined: Feb 2007
Posts: 117
Likes: 1
From: Northern Michigan
92 300TE 4Matic
The diagram shows the visors powered off the dome light so tear into that.
Last edited by MediumKahuna; Jun 8, 2007 at 12:35 AM.
Thread Starter
Senior Member
Joined: Feb 2007
Posts: 270
Likes: 1
From: Western Michigan
2003 E320 4Matic Wagon & 1997 E320
Thanks, MediumKahuna, again. I found the problem and fixed it.
It was the sun visor light contacts. I did not realize the electric contacts were in the clip and used a metal washer and that shorted the contacts. I thought there should be wires going into the visor from the fixed end, LOL.
It was the sun visor light contacts. I did not realize the electric contacts were in the clip and used a metal washer and that shorted the contacts. I thought there should be wires going into the visor from the fixed end, LOL.
