|
|
|
#1
|
|||
|
|||
Low voltage - battery drain
I've had a slightly strange problem develop on my 79 280SE. The battery is slowly being discharged during my stop-and-go commute, especially with headlights/heater/wipers on. I have to put it on the charger every few days otherwise it loses enough juice to be unable to start the car.
Voltage with the car idling and no load (at both battery posts and clamps) is 12.3 V which is kind of low - it's always been up around 13.5 or so. With everything on it doesn't change much, 12.1 is the lowest I saw. I replaced the alternator a couple of years ago (maybe 15k miles) with a Bosch rebuilt unit. The charging light on the dash doesn't normally come on (and I know it works because the belt broke a few weeks ago). It does however come on when I start the car, and I have to rev the engine a tad to make it go out, then it stays off. I guess it's possible the alternator brushes need to be replaced already, but does anyone have any ideas on what else could be going on? I don't think it's the battery. Thanks!
__________________
kalpol 79 280SE 82 Fiat Spider 2000 81 Fiat Brava 04 BMW R1150RT 96 Jeep Grand Cherokee |
#2
|
|||
|
|||
It could still be the battery. If you are charging high amps the voltage will be low, hence the 12.3 volts reading. It's the old flowing water analogy. A shallow river flows fast (voltage) whereas a deep river (charging amps) flows slower.
Load test the battery. If it tests okay then re-check your alternator. If you have an induction ammeter you can check for running amps. You should be showing 13.5 V and about 2 to 20 amps at idle with no accessories on after the battery has recharged the starting amps draw. Last edited by Mike D; 12-18-2007 at 09:14 AM. |
#3
|
|||
|
|||
Excellent, thanks. So I have a multimeter with an ammeter - 10 amps I think it will handle...I've never used it, should I be able to test the charging amps with this?
__________________
kalpol 79 280SE 82 Fiat Spider 2000 81 Fiat Brava 04 BMW R1150RT 96 Jeep Grand Cherokee |
#4
|
|||
|
|||
Quote:
Mike suggested an "Induction" ammeter which measure the current flow indirectly. |
#5
|
|||
|
|||
Nope! You'll toast the ammeter when you try to crank it. If you pull the alternator wire and put the meter in-line you'll fry it when the alternator "spikes" as it receives voltage. Inductive or high amperage in-line is the only way to check (high amperage in-line must be able to handle the cranking amps). Inductive aren't as accurate but you're just looking for a charge indication.
|
#6
|
|||
|
|||
A climate control servo that won't "park" will drain the battery. I went through a couple of batteries before I figured this out.
|
#7
|
|||
|
|||
It's a Euro model with manual climate control. (I loves it). But good point anyway.
__________________
kalpol 79 280SE 82 Fiat Spider 2000 81 Fiat Brava 04 BMW R1150RT 96 Jeep Grand Cherokee |
Bookmarks |
Thread Tools | |
Display Modes | |
|
|