200TQ 70mA battery drain

Kurt Deschler desch at alum.wpi.edu
Sat Aug 25 09:26:08 EDT 2007

That seems to be the concensus that there is something else such as the 
radiator fan is killing the battery. One lister pointed out that it would 
take 8500 hrs to drain the 600AH battery at 70mA.

On this car, the after-run pump is bypassed and I know that this causes 
the radiator fan to run for long periods since it can't actually cool much 
without the pump. Ditto for the injector shroud fan. Maybe I should either 
fix those or disconnect them entirely. I also realized that my aftermarket 
alarm is probably powered by the door lock circuit. If the LED on it alone 
is 20mA, then 35mA is plausible. This car also has the factor alarm.

Regarding the splice, I have been through the charging cables on this car 
before, but it is probably time to check again.


On Fri, 24 Aug 2007, SJ wrote:

>> From: Kurt Deschler <desch at alum.wpi.edu>
>> I have been trouble keeping the battery charged in my 200. Battery and
>> charging system are fine. There is a 70mA draw when the car is off. Half
>> of this is from the door lock circuit. The other half is from the trip
>> computer circuit. Does anyone know if these are expected current draws?
>>   -Kurt
> **** I had a similar problem with the battery. Low charge on it, sometimes
> car would not start up in the morning. The problem was intermittant also.
> If I disconnected the battery at night, I never had a problem with the
> battery holding a charge.
> The culprit turned out to be a bad after run relay for the radiator blower
> motor. The blower would go on at odd hours of the night and drain the
> battery.
> Disconnect the battery at night  for a couple of days. If the battery now is
> ok and holds charge, then you may have an intermittant drain . . .like mine.
> To verify what Huw said about the cable splice, attach a voltmeter to the
> battery and drive around like that. If the voltmeter reads 13.4, then its
> not the splice.
> Another good way to check the splice is to measure the voltage drop across
> the splice/cable. Connect voltmeter negative to Battery +, and voltmeter
> positive to the Alternator output. There should be insignificant voltage
> drop across that cable - maybe 0.10 volts.
> SJ

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