I have a problem where after sitting for 2 consecutive nights, the battery goes flat to approx 8 volts. I trickle charged the battery over a 10 hour period over the weekend and the same occured today after 2 days sitting.
I disconnected the negative terminal of the battery and plugged my test light again the negative terminal to ground and the light lit up. With the light engaged, I disconnected each fuse on a trial and error basis and found fuse C to dim the light but not to shut it off. This was the only fuse that had any effect on the light.

If my diagnosis is correct, could it be something in that circuit and can someone advise next steps?

Or is it the battery that should be suspect here as it is over 3 years old and an aftermarket 780 CCC.
Battery is being charged by the alternator OK as when I last checked last week, the alternator would charge at 13.8 volts when 2000 RPM with heater and lights on.

__________________
Walter Sawczak
1990 300 E
1993 Lincoln Mark VIII
1983 Jaguar XJ6

Seem I have almost same problem on my 1991 190E 2.3L. I replaced an aftermarket battery last week and one used alternator (from my parts car) and 2 Bosch rebuilt alternator. Still not fix the problem.

This morning, bought an orignial battery in...... will drive few more days and see what happen..... will report it later

Hi,

Had the same problem a few weeks. Brought my battery to autozone for a free recharge and it didn't fully charge. The replace battery light always went off on their charger so I had to buy a new one. I didn't have the problem for a week now.

Try this.take an ohmmeter reading between the positive and negative battery terminals(battery disconnected)and report back.using the total resistance you can easily compute current draw by using ohms law.

__________________
michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon

I double check with my mechanic tonight...... 100% sure the alternator and battery are working fine.

End up to take off one relay inside the additional relay box.... the volts back to 13.10V at idle.

Don't know what that relay for!!! Totally, no idea...... It doesn't effect any power windows, starting and fuel delivery....I will find it out.... Will keep update

sounds like like a parasitic current drain in that circuit.ive got the 124 electrical diagrams.if you can provide a little more info on that relay perhaps i can track it down for you

__________________
michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon

Well I have found that the right taillight and dash and console lights were part of a circuit. I replaced a fuse and the lights are working. However in the same circuit the license lights are not. I am waiting to see if there is a discharge over night. At the license plate lights I had no voltage. Does anyone have any advise on tracing this?

__________________
Walter Sawczak
1990 300 E
1993 Lincoln Mark VIII
1983 Jaguar XJ6

Updated my result..... 100% sure that relay problem to drain the power.

Drove the car whole day, no problem..... That relay is for pre-heater intake manifold..... now, take it aways... no more power drain and no effect on cold start and seem improved the performance.

you will probably want to replace that pre heater.ill bet its there for reason.good work on the trouble shooting!

__________________
michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon