Battery keeps draining after alarm system fitted?

[Giffybongo]

Evening all,

A low starter battery voltage had happened recently and the auto electrician we took it to (who not long ago installed the alarm/immobiliser and swap loom) tested the alternator and said this was faulty and was the cause of the batteries being low on charge...he replaced the alternator and we thought that was the end of it.

But then our Bongo starter battery went from a healthy 12.8V to 9V after a long drive home after a trip away and then sitting overnight again. The leisure battery voltage actually went up from 8 something to 9 something volts over the same interval.

I'm thinking it got to be some sort of parasitic drain on the starter battery...and it all only seems to have been a problem since the alarm was installed. I'll be taking it back for the same garage to check, but just wondered if anybody else had the same sort of problem after an alarm install and what the cause might be.

Thanks guys!

[g8dhe]

Its not an uncommon situation where a recently changed alternator fails within a very short time! If you down at 8 to 9v then the battery will almost certainly have been damaged as well. At one time a lot of alternators of a similar type were only rated at 80 Amps and generally failed just over a year, hence voiding warranty The alternator needs to be a genuine one correctly rated at 90 Amps.

[teenmal]

Mazda part number WL0118300