I definitely have a parasitic draw somewhere; brand new battery is dead after a few days of sitting.

I know I can go around and unplug various things until the draw stops, but that would take a while (unplug something, then wait a few hours and test the battery voltage again, repeat until voltage doesn't drop).

To potentially save some time, I thought I'd ask: Is there a particularly common cause of a parasitic draw in our cars?

 

Do you ahve a VOM with low current ammeter?

You can check each circuit in less than 30 seconds using that.

If you get some amp or two current, that is your drain. Make sure your doors are closed so you don't pick up interior light draw.

Doug

 

MrAndersonGCC,

You haven't said what car you've got, as that makes a difference for likely causes.

If it's a late facelift, I'd say start with boot light and alarm system.

Paul

 

This is the vom I have. I’m used to testing ohms and volts, but how do I test the current of a circuit? Just use the DC 10A input and put the ends on one of the glass fuses?

 

It’s a 1983.

 

DC 10A. Plug the red wire into the red circle socket..

Not sure about fusing on that meter, perhaps download the instructions and read them

Doug

 

Just pull each fuse in ti=urn while you measure the drain on the battery with your meter

 

Ok that makes sense, the meter will complete the circuit in place of the fuse. Thanks

 

I pulled every fuse under the steering column and the five in the engine bay, measured for a current and got nothing.

Is there anywhere else I should be testing?

 

I tested again, this time looking for current between the negative cable and the negative post while pulling one fuse at a time. Current read 1.65 amps. Same result, current didn’t change, held steady at 1.65. Any other ideas?

 

Here are a couple:

Mentally cuss out Lucas electric, to start with.

Get a wiring diagram and cuss out the guy who drew it as a wiring schematic, instead of a wiring diagram, and try to figure out where you have an unfused draw.

Get something like this and try various wires until you find the one with current.


.

Doug

 

Cussing complete. Thanks for the links Doug!

 

Found it!

I recently replaced a couple relays in the trunk near the battery when I was chasing another electrical problem.

I didn't have a parasitic draw until recently so I unplugged one of the relays and the current dropped to zero. Put the old relay back on and current stayed at zero. Clearly not all 5 pin relays are the same and I chose poorly.

It was the one with the red plug:

 

Internal circuitry can vary on replays.

The little schematic on the side of the relay helps quite a bit, and sometimes very minor variation in the schematic, may go unnoticed unless you get a magnifying glass out. I noticed there is a relay or two that is hard to find a replacement for, but don't recall which ones they were.

Doug