What's a typical drain on a battery while connected to a car?

[rickpaw]

My car is a 67 Firebird, with 5.3/4l60e swap. The vehicle wiring had been replaced with American Autowire classic update kit. Engine harness is from PSI wiring. Battery is located in the trunk.

The other day, I hooked up my meter in series to the battery neg post, and it read around 0.5A (everything was off). I pulled the relay for the PSI harness main fuse panel, and the reading dropped to 0.002A.

Wonder if these numbers are normal?

[mitch_04]

Most every time I look up the allowed drain on newer vehicles while chasing a draw, its .25 amps or less.

[dontlifttoshift]

When you got .50 amps, who long had it been since they had been on?

I don't recall the actual timing but it takes a while for the ecm to go to sleep mode.

[rickpaw]

Originally Posted by dontlifttoshift

When you got .50 amps, who long had it been since they had been on?

I don't recall the actual timing but it takes a while for the ecm to go to sleep mode.

The car had been sitting less than 24 hr since I last ran it, when I made the measurement.

[68EFIvert]

I had a very similar situation with my Ford harness. I eventually tracked it down to a relay that was stuck in the open position. It was a real pain in the rear to find though.


Darreld
Sent from my iPhone using Tapatalk

[dale68z]

Originally Posted by mitch_04

Most every time I look up the allowed drain on newer vehicles while chasing a draw, its .25 amps or less.

yes.

Make sure you allow the system to time out. I have had to wait an hour sometimes.

[rickpaw]

Originally Posted by 68EFIvert

I had a very similar situation with my Ford harness. I eventually tracked it down to a relay that was stuck in the open position. It was a real pain in the rear to find though.


Darreld
Sent from my iPhone using Tapatalk

Now think of it, I think the relay for the engine harness may be stuck also. Pulling the relay should not make any difference in the amp draw, correct?

[mitch_04]

How we find them is take the negative battery cable off, hook up a multimeter between the cable and the post with the multimeter on amperage setting, and then start pulling fuses until the draw drops. Have the door open but the door switch closed, that way you can access interior fuses but it won't be trying to turn on the dome light and similar accessories. You can also use a test light in place of the multimeter, just wait for the light to go out when you pull a fuse. However, with a tiny draw it's hard to see.

[rickpaw]

Originally Posted by mitch_04

How we find them is take the negative battery cable off, hook up a multimeter between the cable and the post with the multimeter on amperage setting, and then start pulling fuses until the draw drops. Have the door open but the door switch closed, that way you can access interior fuses but it won't be trying to turn on the dome light and similar accessories. You can also use a test light in place of the multimeter, just wait for the light to go out when you pull a fuse. However, with a tiny draw it's hard to see.

That's what I did. Pulled the main relay feeding the engine harness fuse panel, and the amp draw dropped from 0.5A to around 0.002A.