Parasite voltage loss

[nzcarguy]

Hi All



Looking for any ideas, the other day I forgot (DA) to disconnect my battery and shorted the starter cable/battery feed. No fuses blown.

I disconnected the battery earth, left the positive on and found the battery dead. recharged, then replaced the battery but I have I have .2 mili amps draw without the earth connected.

LS3 crate with GM ECU in first Gen Firebird.

The wiring has 4 separate circuits from the battery.
1) OEM wiring harness - lights etc
2) Vintage Air
3) ECU
4) Alt/starter

I have disconnected each circuit and measured the milli volts each time. No change for 1,2.4 leaving only ECU.



Has anybody seen this problem and where on the ECU should I be looking for a short?

Thanks in advance.

[dhutton]

A lot of odd things being stated here imho.

Measuring things without the negative of the battery connected is a bit odd and really doesn’t give any useful data imho. I think maybe you are measuring some kind of galvanic voltage which is not something I would worry about. It has nothing to do with parasitic current draw when the battery is connected. Unless I am misunderstanding and you are measuring the current to the negative terminal of the battery.

Short circuits don’t draw .2 mA. They draw a lot of current...

Your ECM will have a small standby current when the key is off. That is just the nature of the beast and nothing to worry about imho. Put the car on a battery tender if you go for weeks without using the car.

Don

[absintheisfun]

I'm not sure how you are measuring a draw with the battery disconnected. If you have it connected (ideally with the meter on the ground side) anything below 50 milliamps is considered acceptable. With a healthy battery, it would take over two weeks to discharge.

Also note that its best to have a healthy battery when doing a draw test.