Battery drain

[DomP182]

My 172 is draining the battery aver the course of a week or two, how do i go about testing with a multimeter to diagnose the cause?

 

[Rystar]

You're gonna want to do a parasitic draw test by the sounds of things, YouTube is awash with videos explaining how to do this however this one below seems to be fairly good at explaining the reasonings/method on how to do this. hopefully is helps

 

[JamesBryan]

Set the multimeter to Amps DC, take the -neg wire off the battery (fully charged), stick the black probe on the battery and the red probe to the cable you've took off the battery.

Then start unplugging things and watch for the current draw to drop.

I'm guessing alternator diode pack.

 

[DomP182]

That's my Sunday morning sorted then

 

[JamesBryan]

Start off on one of the highest amp settings and work your way down until you get a reading, otherwise you could blow a fuse in the meter. A decent one will have some protection overload though.

Not that it'll be drawing loads anyway I wouldn't imagine, a couple hundred milliamps at most.

 

[DomP182]

Thanks I think I understand

 

[DomP182]

Ah now I'm thinking it could be linked to my interior lights not working when either door is opened and the fact my alarm will go off when unlocked with a door open

 

[DomP182]

I got a reading of 0.022 doing the test you suggested James so that would suggest I've got no problem with parasitic drain right?

 

[JamesBryan]

What scale was that on with your meter?

 

[JamesBryan]

Is that 22 milliamp?

That's nothing if it is, 100-150 milliamp is considered ok.

 

[DomP182]

Good question, that was on my auto ranging multimeter using the Amps rather than milliamps setting. Can you tell I haven't much of a clue what I'm on about.

When opening boot, drivers door etc I got around 4 amps, interestingly though not with the passenger door so would that be linked to my interior light not working when doors are opened?

 

[JamesBryan]

Probably yeah, check the switch in the door.

 

[DomP182]

Probably yeah, check the switch in the door.

Had a look, it's damaged so might be the problem except the interior light won't work with the drivers door either even though I can see it drawing power when open. They work on the switches however

 

[JamesBryan]

Odd