Tracing a short in a 240D?

My old 240D has never had electrical problems until now, when it may have been caused by a lot of rain we had recently. I need to use it or I'd leave it a few
days until things dry out a bit.
All the fuses are intact. The brake lights are not working. The battery is quite young and not the problem - starting is very easy.
I switched to different positions and looked to see what was on.
Low beams - rt turn light, and two rear lights - the ones next to the turn signals - are on High beams - rt turn signal, both headlights and the same two rear lights are on . Off position - all lights off
Possible the switch needs cleaning, or can it be taken apart at all?
Thanks for all comments and links to possible troubleshooting techniques.
RF
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The brake lights in my '80 don't light unless the ignition key is "ON".
That may also be the case here.
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First of all... go to your fuse box... rotate all the fuses until they are all freely rotating... these fuses are notorious for looking okay when they are not. I suspect your both your low beam fuses may be oxidized at the contact points.
As for your brake light, it is possible you may have a bad brake switch if you still cannot get it to work with ignition key on.
left turn light bulb... probably burned out.
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they
Thanls TGL and T for the suggestions.
I took out the fuses cleaned the ends and vaselined them - then reinstalled and rotated them. Then I cleaned and vaselined the battery terminals.
The brake lights do work only with the ignition on. Another driver helpfully told me that they were not working or I would probebly still be driving.
Didn't help.
Thanks anyway.
RF
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are
if
reinstalled
helpfully
My manual is nowhere near me right now so I decided to do a few other jobs on the car this afternoon. After I was done the blinkers worked again.
I think it's drying out. Fingers crossed :-)
RF
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That sounds kind of unacceptable to me...
I don't think I would want top be driving a car in which the brakelights go out when it gets too wet...
Marty

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Thanks M J.
You're right about that. I will try to track down the cause.
We get only about six rainstorms/year here so the problem woulnd't occur too often - if that's what the problem is. I believe there are sprays that can run water off electrical systems and I'll check into them
RF
said:

jobs
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If the trunk leaks, that would be a possibility, if not, it's probably along the firewall somewhere...
Pretty simple circuit luckily, even if you have to run new wire for those lights...
Marty
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said:

too
Thanks Marty.
The dry out didn't help. Problem is I don't really know where to start tracing without a wiring diagram. I have a manual but it will be some days before I can get to it. I searched for a wiring diagram online but couldn't find one.
The trunk has leaked in the past, if I parked the rump uphill. In the present case, there was no leak.
By firewall, I take it you mean the barrier between the inside and the engine box. I could trace the wiring through there and check if the insulation is worn away.
The high beams still work. Everything else is screwy.
Thanks again
RF
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just for the hell of it check the ignition switch. if they only worked with the car running the plug may not be fully pushed in or be starting to go bad <or the tumbler contacts could be going the same rout>
the case, minus a few cans!
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Thanks Pool Man.
I checked a few things today and the some of the lights, e.g. the blinkers, and one brake light work intermittently. Some lights, e.g. the headlights, work with the ignition off, which I think they shouldn't. I pulled the plug off the brake switch and shorted it out - the brake lights didn't come on. I assume that the pedal switch shorts it out too. The high beams always work and the low beams light the left lamp only.
I checked most of the plugs in sight - pulled them out - vaselined the contacts and replaced. The wiring looks like new - which is probably not a surprise - the car has only 85K miles and was garaged for most of its life.
As you suggested I had a look at the ignition switch but didn't get much further. The black plastic piece that the lock is built into fits into a steel casting that has a short tube attached with a clamp to the steering. I undid the bolt of the clamp but the casting doesn't want to come out - it hits something metallic, when I pull on it. Are there wires passing into the steering column through that tube? There are several cables attached to terminals on the casting. Anyway, the wires to the switch seem large so I think it may not be the problem..
HHHHHHHHHHHeeeeeeeeeeeeeeeeellllllllllllllllllllllllllllllllllllllllllllllll llppppppppppppppppppppppp!!!!!
RF

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the ignitions on MBs are bullet proof. i have never taken one off my self but thought you could get to the plug, sorry.
i would get out your ohms meter and test all the bulbs in question and then set it to DC and check for power <2 people> to the plugs as for the headlamps they will turn on with out the key but on mine the FLASH TO PASS does not flash
you may want to check the STANDING LAMPS <head lamp switch to the left with the key in the OFF POSITION.
the case, minus a few cans!
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If the brake light switch isn't working, I think getting a multitester and make sure there is power there... If not, go back to the fuse box and test there...
I don't know about the vaseline thing either, i wouldn't use it that way personally, too big a mess. I like the deoxit spray, used VERY sparingly...
Pursue one simple problem at a time like the brake lights first
Marty
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said:

HHHHHHHHHHHeeeeeeeeeeeeeeeeellllllllllllllllllllllllllllllllllllllllllllllll
Thanks again P M and M J.
The brakes have no electric power at all and it's no surprise - see below.
This morning I switched the ignition on and tested the supply to the fuses. Only fuses 1, 2, 4 and 6 are live. The brake light is on a fuse with no power. Now I need to get at a manual to see the lines between the ignition switch and the fuses.
Vaseline is known as a good conductor and it slows the oxidation (corrosion) of metals. It's very commonly used on electrical contacts.
Anyone know if the ignition switch comes apart? It's hard to get the metal casting, that the black key block fits into, away from the steering.
RF
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