Hello guys I have a small problem with my newly accuired 300td. The car has been sitting for a good deal of time. I replaced the water pump and hoses. I put a new battery in it and it has been running good. The battery goes dead after a couple days. I have to jump it. I checked with the engine running and at idle it is 13 volts. Revved up a little over 14 volts. I unhooked the battery and placed my fluke meter to check amps. It is showing a 5.9a draw. I did it at night and there is a big spark. What could cause this amount of draw? Thanks guys for all the help. Robert

Pull one fuse at a time to find the culprit circuit.
Then narrow it down from there.
Good old fashioned wire chasing.

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Cheers!
Scott McPhee

1987 300D

That sounds like a plan. Is 6amps a large draw? I haven't got to test it yet and pull them.

Way way too big no-load draw.

You should see less than 50 mA draw on a stock 87 300D.

__________________
Cheers!
Scott McPhee

1987 300D

Mine is a 1982. Thanks for the help I will pull fuses tomorrow. Is there any way it could be the alternator?

sure, it could be the alt, but since yours is charging, it's best to start pulling fuses until the draw is found.
6 amps is huge, and would certainly kill a battery in short order...

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My drivers:
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1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I had a similar issue in my old Ford Ranger and it was the ignition switch that was drawing the power. I'm not familiar enough with the electrical on these to know if it could be the problem but it's something to think about.

Unplug the GP harness.

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1995 E420 Schwarz
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#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I pulled fuses and found the problem. It is the power antenna. I had a guess that was the problem. I don't know if it's the switch or actual motor. I unhooked the motor and found .01amp draw with it hooked 6.42amp thanks guys.

Great job of diagnosis.

Is the antenna motor still running? Can you hear it run/stop, or at least hum when you remove the fuse and put it back in?

If you have a helper, run the antenna up and down, listen to the motor and watch the ammeter. If it shuts off in one position but keeps drawing amps in the other, an 'end switch' is failing to tell the motor the antenna has reached the end of its travel and keeps the motor energized.

Oh, and 6.4 amps at 12v is the equivalent of a 75 watt light bulb, so the antenna motor housing should be pretty warm!

Update. I jump started the car last night. I put the fuse back in and took the wiring loose from the antenna. I was checking the amperage from the negative side. Does it matter what side i check it from. I had to jump start the car last night and it started up well. I let it run maybe 10 mins. I should have taken it on a short drive. I shut it off and started it up 3 times with no problem. This morning i tried to start her up no dice. It rolled over real slow. I guess its back to trouble shooting. Thanks guys.

http://www.peachparts.com/shopforum/general-information/273454-never-disconnect-battery-cable-engine-running-test.html


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I never disconnected the battery while it was running. It has been off with all tests performed. I'm sorry for the confusion.

Hi; Try the trunk light switch ! Mine was faulty, giving the same problem;

I posted it for clarification of new owners that might make the mistake.

A clear warning can save them from damage.

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