Battery keeps getting drained

[Stevoyayaya3]

So my battery won't hold a charge on my m42. About a week ago I changed the oil filter housing gasket and out everything back the tension on the alternator feels the same maybe just a tad more slack. Any idea what could cause it or the first thing to check? If I get my car jumped it will drive fine until I cut it off. Thanks in advance guys

[jalopi]

How old is the battery? Some of the cheaper ones are only good for a few years. Anyway...

Check the static battery voltage.

If it's above/around, say, 12V: check the cranking voltage of the battery. If it drops below 9-10V during cranking your battery is shit, you're gonna have to replace it.

If it's below, say, 12V: you need to do a draw test to see what's killing your battery.

I'd do a draw test even if you replace the battery, just to be sure.

[Stevoyayaya3]

Ya I did take the battery to autozone and they said the battery was bad. I had put a smaller battery from my 92 civic in and it killed that in a couple of days. Exactly how would I do a draw test? Thank you

[jalopi]

Read this:

http://randysrepairshop.net/testing-for-battery-drain.html

You need a multimeter. Make sure you don't hook it up in parallel or you'll kill the meters' fuse. Don't work the windows, radio, any controls, ect or you can kill the meters' fuse.

[Stevoyayaya3]

Just updating for maybe someone who has had this problem. My mechanic had my car for almost 6 months and couldn't figure it out, but I did a little research and changed out the voltage regulator and the problem was solved. Just make sure to get the correct regulator

[Stevoyayaya3]

And now it's doing the battery drain again. Wtf lol it's been running great for about 5 months lol

[long tall eta]

And now it's doing the battery drain again. Wtf lol it's been running great for about 5 months lol

check the batteries in your cluster. if bad, you can suck your battery dry.

[Stevoyayaya3]

Like on th si board? I bought a refurbished one from bma about a year ago

[e30onBBSs]

Battery keeps getting drained

Check the connections of your cluster, I read somewhere that if not connected the battery won't charge the car for some reason. Also do you have an aftermarket alarm? I've also read/ heard those can be a battery sucker if installed incorrectly or left on or something

[Stevoyayaya3]

It was the alternator even though the alternator tested fine lol

[TobyB]

Wow- and you lived with it for that long???

hee

t

[estoguy]

Was the entire alternator dead or just the voltage regulator? I had a similar condition a couple years ago, and it was regulator. Easy fix.

[Gregs///M]

Like on th si board? I bought a refurbished one from bma about a year ago

Dont trust those BMA SI boards. IN fact don't trust any SI boards from them, E30_dad or Programa. We repair their SI boards almost weekly.

They only change the batteries and capacitors. There are about 15 transistors and voltage regulators which are responsible for the parasitic drain. If the batteries are new, the transistors are still 30 years old and will intermittently and rapidly switch on and off, even with the car off. This is what causes the parasitic drain.

If your drain is coming from the either fuse 10, 12 or 21, there is a good chance its the SI board still, super common.