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Old 08-09-1999, 08:26 PM
Posts: n/a

My 1985 300CD has developed an annoying

habit of late. After 3 or four days of

driving or sitting (it doesn't seem to

make a difference), the battery runs down

and won't start the car. I have replaced

both the alternator and the battery (both

tested bad) and the problem persists.

I hooked up an ammeter between the

disconnected positive battery cable and

the battery post. The only draw was 2 amps

lasting for about 5 seconds out of every

30 seconds. I suspected that was the clock,

and disconnecting the fuse for the clock

circuit ended the draw. Please, this is

making me crazy!! Any helpful suggestions

you can make would be greatly appreciated.

Bosch certified DFI Tech
20 years experience
MBCA Member, Southern Stars
Old 08-09-1999, 08:46 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
It is somewhat common for the Pre-glow relay to stay on after starting the car. Since the glow plugs take about the same amount of current as the alternator can put out the battery will go dead. Other than testing the charging system after every start or disconnecting the glow plug harness, replacement is a good bet.


Old 08-09-1999, 09:23 PM
Posts: n/a
Rest current draw on this model should be no more than 30mA. 2a draw from the clock? This test is best done neg termal to neg post. Connect ampmeter leads then touch the termnal to the post for aprox 15sec. to cycle every thing off. Key out of ign and doors closed.
Good Luck.
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