After a recent rainstorm, I lost power to my lights, including brake lights, the gauges and tachometer don't work, the rear interior light doesn't work nor do several dash warning lights.

I checked the fuses and found that several fuses are not being supplied with power. The lights work only if I use the switch.

Also there is a relay in the box behind the fuse box that is buzzing with the engine running.

I removed the under dash panel and carpeting on the drivers side to try to trace power from the ignition switch to the fuse panel but haven't found anything yet.

I found a post about a similar problem but no solutions.

This seems very strange, such a major power interruption should not be too hard to find but I'm not sure if I'm on the right track.

Any help is very much appreciated.

Acky

Is there any relation to the fuses which have no pwer supply? Such as being in a straight line either across or front & back?


Gilly

No there does not seem to be any relationship, the fuses that have power with the engine running are, from left to right starting at the top;

A, 1, 2, E
B, 6, 7, F
C, 9, 10, G
D, H.

FUSES WITHOUT POWER ARE,
3, 4
5, 8
11, 12
13, 14, 15, 16

Thanks,
Acky

Maybe someone will have a bright idea for you, otherwise i can study this a little tonight. I have the schematic and also an actual fusebox I can look at if I need to (a new one).
In the mean time, can you post a more exact list of what's inop. What I'm curious about is which warning lights on the dash don't work, and also are you saying NONE of the exterior lights are working? You said brake lights, but also headlights, turn signals, backup lights, license lights, everything ?

Gilly

Well Gilly, with the ignition switch on, the only dash warning lights that come on are the battery, ABS, and SRS.

The high beam, parking brake, low brake pad, oil pressure, water temp, low washer fluid, and the lamp failure warning lights all fail to light up.

When I start the engine the following gauges do not work, fuel level, water temp, oil pressure, and tachometer.

With the engine running, the headlights and driving lights should come on but they do not. No headlights, running lights, or license plate lights, however, these all come on when the headlight switch is turned on.

The brake lights also do not work.

Turn signals and flashers do work.

Fuses that do not have power when engine is running are #s 3, 4, 5, 8, (11, 12,both empty) 13, 14, 15, 16.

I hope this makes it clear.

Thank you for your help.

Acky

OK Acky, I'll try to get back to you on it, sounds "interesting" to research (sorry if that makes you feel like a test-subject).

One thing I don't understand is when you say:This makes no sense, these don't come on automatically, the switch needs to be put into parking lights (for the "running" lights and license plate lights) or Headlight position for the headlights to come on, unless there is some weird mod done on your car which I'm not aware of. This IS a US spec car right? when you say "driving" lights, do you mean the fog lights or the parking lights?

Gilly

Update:
Check fuses for power again with headlight switch turned on, also try various combinations when checking these fuses, especially high beam/low beam, I believe some of these it is normal to have no power with the headlights off:
13 & 14 I believe will be hot with low beam, 15 & 16 I believe will be hot with combination switch in high beam.
Fuses 3 & 4 headlight switch has to be in any position other than off, and also same with fuse 8.

After more reviewing, alot of what you seem to have going on seems related to fuse 5, which is circuit 15. There are other fuses that would drop out and alot more problems if it were a problem with the fusebox itself or the ignition switch.
At this time it would make sense to REALLY scrutinize fuse #5 itself (pull it and look for a small crack in the metal or corrosion on one of the tips) and also check the "base" (or bottom connector) of the #5 space in the fusebox for power with the key turned to "on".

Let me know how your doing. The #5 fuse covers alot of the problems you're having with the car, to quote the fuse list:

"stop lamps/dome lamp/lamp failure monitoring unit"
"warning indicators/gauges/clock/tachometer"
"cruise control"
and as of end of model year 87, the warning system

Gilly

PS Circuit 15 is not a fuse number, what circuit 15 means is a circuit which is "hot" or "live" with the key in position 2 ("run" position on the ignition switch)

THANK YOU GILLY, THANK YOU, THANK YOU, THANK YOU

I JUST GOT HOME AND READ YOUR POST, I WENT OUT TO THE CAR WITH A FLASHLIGHT AND A NEW FUSE, SURE ENOUGH THERE WAS A HAIRLINE CRACK IN THE 8 AMP FUSE, REPLACED IT AND THE DASH LIGHTS ARE BACK TO NORMAL, WHEN I START THE ENGINE THE HEADLIGHTS AND RUNNING LIGHTS CAME ON AND WORK FINE. ALL OF THE FUSES IN THE FUSE BOX NOW HAVE POWER EXCEPT 15 &16, WHICH ARE FOR HIGH BEAM.

In hindsight the problem started after a rain, water had gotten in to the engine compartment and drivers foot well, I compared power in the fuse box with another 300E fuse box, both cars have daytime running lights so I was looking for an interruption before the fuse panel (circuit 15). I don’t know why fuse 5 causes several other fuses to be powered.

I thank you and appreciate your help and effort in helping me with this problem; I could not see the tree for the forest. I have ordered a seal and will waterproof everything. I so value your advice that I will replace all of the fuses in the box.

God bless you,

Acky

Glad it worked out for you.

15 & 16 are actually provided power by the high beam switch (combi switch it's called), so if you turn on the high beams 15 & 16 will then have power. Kind of have to think of it backwards.

I don't think it is a matter of fuse 5 being cracked causing other fuses to not have power, it's a matter of testing the fuses with the switch on. The only "real" problem was fuse 5 being cracked, I am very confident of this. It is a kind of backwards way of doing this, the power is going through the fuses AFTER the headlight switch (or the high beam switch in the case of 15 & 16) on all of those fuses you mentioned except fuse 5.

Never heard of the daytime headlight (DRL) feature being implemented on a 124 chassis. Is that a kit, or just a wiring change or what?

Gilly

Hi Gilly

The 92 and 90 300E both have daytime running lights, with the ignition on, all the driving lights come on (to turn the fog lights on you must first turn the headlight switch to on.) I guess this DRL is for Canadian safety standards/regulations etc.

when I checked the 1990 300E fuses with the engine running every fuse except 15 and 16 had power to it.

Then I did the same check on the 1992 car that had the problem, I found that six fuses had no power (not counting 15 &16) that got me looking for a major problem.

After replacing the faulty fuse #5 from your suggestion, the other five fuses now had power. I re-checked it today by checking for power before and after removing fuse #5 and the same thing happened. I don't know why it does this.

I learned (remember now) the proper way to test a fuse.

Thanks gain for your help,

Acky

I just realized that although it doesn't mention in the fuse chart, fuse 5 must supply power ALSO to all DRL, thats why I normaly have power to the other fuses withought the headlight switch turned on. When I removed fuse #5, I lost power to fuses #3, 4, 8, 13, and 14.

So on a vehicle withought DRL, as you stated, these fuses would only have power when the switch is on.

Thanks

Acky

Uncle Acky:
Yes, this may be the root of my slight confusion right there. I didn't realize that either you're in Canada or that this is a Canadian spec in the US car. Maybe it would be to your benefit to list either your province or at least "Canada" behind the name of your town, as I would just assume it's a US spec vehicle (and I checked your "location" before I responded).

I'd rather not fire up my 124 disc again, but yes fuse 5 is a busy little fuse alright. I have no info on how they wired DRL's on the 124, but I'd assume that it could play a role in DRL, sure. There are still those 2 other fuses that are just for high beam, which won't have any power unless you test for power with the combi switch in either high beam or the "flash to pass" position (lever either forward or manually pulled and held back). And I believe you are 100% correct, if the headlights are wired to be on with the ignition switch on or the engine running, then I would also expect that the 2 low beam fuses would be powered up with the ignition switch on or engine running, unless I saw that maybe MB used a different path of some sort to the low beams (unlikely) or they had seperate bulbs in the headlights for DRL (more likely than a different path, but also sounds false by what you are telling me). Does the 124 DRL system activate only the low beam headlight bulbs, or does it also activate the tail lights and license plate lights?

I would assume that because Fuse 5 is circuit 15 AND provides some of the power to the lamp failure monitoring unit, that this would maybe be the cause for lack of DRL's when fuse 5 is blown. The failure monitoring unit actually provides power to most if not all of the exterior lamps to the car, but not sure if it does for the headlights or not. But I would think that the failure unit would somehow be involved in the DRL system, and the way it would know to activate the DRL's is by getting a circuit 15 signal, which fuse 5 would I assume provide.

Gilly