Trying to track down why the battery discharges this 300D I'm moving around. Belongs to the guy selling me an SD, so I'm shuffling his cars around while he's out of town. So he's just been disconnecting the the negative cable, and when you put a meter on it it shows full voltage on the circuit. That means something still leaking current right? I only know boat electrical systems, so any tips would be great, searching also! Plus I pulled the fuses one by one watching the meter (dropping one down the tiny hole in the corner of the fuse box, leading to unbolting it to get in there with tape on a wire ) , and the meter never changed. Does the positive go straight to the starter and then out to the system or is it branching off where I can't see it? I have the CD but on Mac it's just an endless list of pdf files, it doesn't actually run...

Hello 240dnewbie
You need an AMP meter.
Make sure that all lights are off, remove trunk light bulbs rather than guess.
Disconnect the negative terminal on battery.
Connect the amp meter from the negative terminal on battery to negative cable.
Watch the meter for 90 seconds, (some after market accessories take that long to return to rest state).
There should be minimal 1 amp or less or no draw.

Post the reading you get, we can probably guess what is wrong from the amp draw amount.
Have a great day.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

So the trunk lights bypass the key switch?

Hello 240dnewbie
All lights bypass the key switch.
Separate circuit.
Many electric circuits bypass the key switch.

O.K. the current is .27 amp. I'm using the type of meter that clips around the wire, and didn't see any flow back at the trunk light switch. Any other good places to start looking? BTW, the value of the volt test is for somebody who can't go grab an ammeter is it will show a leak, no matter how few milliamps, which at least let's you know its not the battery self-discharging because of an internal short.

Hello 240dnewbie
Best guess is clock at 0.27 amp draw.
Something is not right here; if the battery keeps going dead.
What is the time frame for the battery drain, one day, one week, three months?
Follow up testing.
You need:
#1. Starter cranking amperage draw test.
#2. Alternator; Voltage and amperage out-put test data.
#3. Battery load test data.

If all of these come back ok; repeat the amperage draw test every day for five days, it may be an intermittent short or random sticking relay.