Battery discharge after heavy rain

[AlexKing]

So car is a sedan with an m42 swap. Battery is in the engine bay

After heavy rain the battery will almost completely empty. I have a rust hole in the cowl but from the look of it would only let water into the same place the black grille/vent things would.

Another observation I made is that if the nose of the car is up it doesn't seem to be effected.

I haven't got a multimeter yet but i will be getting one soon to help track down this but was just wondering where people would suggest i start.

[TobyB]

..plug the rust hole...
Then check the alternator- it's always connected to the battery,
and the diodes in it can start to leak current as they age.

Then the usual trick- pull the fuses one at a time and check for current across each.
You're looking for a drain of .050 amps or more- if it drains overnight, you're looking for
a lot more than that.
If it only does it wet, then you get to test it when it's wet...

hth

t

[AlexKing]

..plug the rust hole...
Then check the alternator- it's always connected to the battery,
and the diodes in it can start to leak current as they age.

Then the usual trick- pull the fuses one at a time and check for current across each.
You're looking for a drain of .050 amps or more- if it drains overnight, you're looking for
a lot more than that.
If it only does it wet, then you get to test it when it's wet...

hth

t

rust hole is getting plugged ASAP. Haven't been able to do it because of rain and other commitments.

I think I have it fixed though, pulled out an aftermarket security system the other day and the battery has survived a massive downpour.

I guess time will tell