Battery Drain/Dash lights

[tomski]

Hi, I have been having problems for a few months now with the battery dying on my 1992 325 cab. When I start the car the dash warning lights wont go out untill I rev the car to 3000/4000rpm and they then go off and stay off but today they have started to stay on all the time not at full brightness but bright enough to see. I have checked across the battery with a tester and I got a reading of 13.78v with the car running. Does anyone know if this is about right for when the car is running
Thanks Andrew

[domross]

Think that reading is a whisker low...should be ?14v? with lights/heaters etc. on...had this problem with warning lights tho , fixed with a new alternator...I'm sure Brian'll probably come up with a cheaper alternative if there is one to be had...my lights/heater also brightened/dimmed with revs...if this happening could be your regulator

[march109]

I have this problem too, ended up replacing the battery but the problem is still there.

I fear its an alternator problem, but I'm servicing mine next weekend and I'll replace the alternator belt first as I do get some slippage and I'm hoping thats the cause.

[tomski]

Thanks for the replys. I have an old alternator from this car I swapped it for a second hand one when the battery draining problem first started. Is there a way that I can test the alternator off the car. I have just pulled the brushes out of it and there seems to be lots of life left in them but I dont want to put this one back on if itsa dud aswell
Cheers

[Brianmoooore]

If the dash lights don't go out until high revs, then it has to be an alternator fault. There's a distinct possibility that you also have another (original) fault draining the battery, and simply added a second fault by changing the alternator.
The big mistake was, once again, swapping parts at random without testing.
Check for a current drain from the battery when the engine by removing the neg battery wire from the battery and placing a current meter between this and the battery neg pole.
Open a window first, in case an alarm decides to lock you out.

[march109]

Brian, could it not possibly be the belt slipping then? will try your suggestion tomorrow.

My symptoms are similar, but... sometimes lights go out straight away, sometimes after I rev the engine or start driving. Sometimes I can hear a belt slipping when this happens particualy when I have lights.heater, demister on ect.

[tomski]

Thanks Again for the replys, just been out to put the car in the garage and noticed that the brake pad warning light only comes on when the car is being started not with the ignition, Related?

[Brianmoooore]

Brian, could it not possibly be the belt slipping then? will try your suggestion tomorrow.

My symptoms are similar, but... sometimes lights go out straight away, sometimes after I rev the engine or start driving. Sometimes I can hear a belt slipping when this happens particualy when I have lights.heater, demister on ect.

Your belt obviously needs sorting, so change/tighten it and go from there.

[tomski]

Just been out and checked with a tester from the battery to the battery lead and it comes up with 11.60/.80v is this within normal range?

[Brianmoooore]

Just been out and checked with a tester from the battery to the battery lead and it comes up with 11.60/.80v is this within normal range?

No, that's a voltage. You need to be on a current range!

[tomski]

Right try again, tried it on a 10A max setting? and came up with 0.10 does this sound more like it.
I swapped the old alternator because I took the car to a local garage who used a snap on tester for the alternator. They connected it to the battery and the red light should have come on but it would only light now and again. They also used a tester that they put between the neg term of the battery and the lead and had the car running while this was connected and said all was well, even with the engine switched off they could arm the alarm to see if that was the problem but they said it was still within range
Andrew

[Brianmoooore]

If that means 0.1 amp, then that is certainly on the high side (about 2x - 3X ) normal, but not enough to cause battery problems on a car in normal use. Try it on a lower current range ( 2amp then 200mA ) for a more accurate reading.
Similar with your voltage reading across the battery! Lowish at 13.78V, but not that low.