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1999 SLK 230K
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3 Posts
Discussion Starter #1
Hello
Recently bought a 1992 300E petrol saloon (or Sedan as in USA) as a non runner. Been stood for a few weeks. Once the battery was charged it started but cut out when warm. Sorted this by changing the fuel filter, cleaning the fuel pumps and lines and changing the distributer cap and rotor arm. Now runs well but if I leave it unused for a couple of days the battery goes flat. Alternator etc all checked and working. An ammeter across the battery shows a 1 amp current so I think there may be a discharge fault rather than a duff battery. With the ignition off one of the relays behind the fuse box ( marked 'A') intermitantly clicks. With the relay removed the car starts, runs, all the lights work etc. Think it it may be the source of the problem, or at least a starting point....

Anyone got an idea what this relay does?


Thanks

srwoolf
 

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'97 E420, '86 Mustang GT, '88 GT, '89 LX
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269 Posts
You may want to use the search feature, and also use the DIY section in this forum. There are a lot of great resources here to try and figure things out yourself, wish I could be of more assistance.
 

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2013 E350 sedan, 2013 E350 cab, 1993 400E sold,1999 ML320
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2,436 Posts
central locking or an aftermarket alarm or even after market stereo (sub woofers) will usually cause discharge. Pull each fuse until draw stops. Then youll have it narrowed down unless they ran wires that are to unfused ones like stereo.
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,394 Posts
Ditto on aftermarket alarm, aftermarket stereo......or bad door lock mechanism-bad vacuum pod, worm vacuum motor or leaking hose connection. For a test, you could disconnect the central locking system and see what happens.

Kevin
 

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1988 M-BENZ 300E | 1991 FORD PROBE GT TURBO | 2003 FORD EXPLORER 4x4
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684 Posts
I'd hook up the amp meter then remove and replace each fuse until you find the circuit causing the draw.

If none of the fused circuits are causing the draw then I'd look at the possibility the alternator's circuitry is bad and causing a draw.


P.S. Tires go flat, Batteries go dead.
 

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1999 SLK 230K
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3 Posts
Discussion Starter #6
Cold wet and still raining here. Call me old fashioned but I think I will not be trying to fix an electrical fault during a monsoon. Have tried removing all fuses with meter in position. There was a draw but this has disappeared. Hmm. The car has no radio ( Thanks to our local Thievery Corporation and a lack of nails long enough to secure the car to the ground anchor). It does however have all the electrics for an in car mobile phone. I'll start looking at that when its dry enough not to have to swim for the kerb.

As for batteries going dead instead of flat. Dead sounds just so terminal.
 

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1988 M-BENZ 300E | 1991 FORD PROBE GT TURBO | 2003 FORD EXPLORER 4x4
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684 Posts
You need to do the fuses one by one then look at the associated label of the one that makes the draw go away.

You can say battery discharges instead of goes dead.
 

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1999 SLK 230K
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3 Posts
Discussion Starter #8
Cheers guys,

The fault appears to be the drivers side window motor. Not sure how as this should not be live with the ignition off. But when its fuse is in , the is a 1 amp draw and when fuse is out there is no draw. When you replace the fuse there is no draw until you start the engine. ON shut down its leaking juice again.

Still don't know what that relay does though. According to various wiring diagrams, it either doesn't exist or is for the electric front seats. My doesn't have the electric seats.

When I find out what it does I'll let you all know.
 

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'97 E420, '86 Mustang GT, '88 GT, '89 LX
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269 Posts
Sounds like you may need to replace the ignition switch, as it continues letting power trickle to the window motor. Which still doesn't really make sense as the window doesn't operate itself, it receives power from the window switch giving it power up and down. When the switch is not depressed, it should not be drawing current.
So, I'd check the ignition switch and window switches for faults.
 
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