Battery discharge problem on Saab 900 classic

dhog4n

Hi, maybe someone on here can help me with an annoying problem: I have a 1993 Saab 900 classic that keeps discharging its battery. Any ideas as to what the cause might be? It has a new battery as of 3 months ago and the alternator does its job but it won't start ofter only 2 days standing.

I have taken to disconnecting the battery leads every time I park up at home but feel this should not be necessary even on an old(-ish) car. The alarm is turned off permanently and all the interior lights switch off in the normal way when the doors are shut.

Any ideas would be appreciated!

carchaeologist

Boot light staying on?Maybe theres a light that lights up under the bonnet staying on?Could be something silly like that?

dhog4n

Hi, The boot light switch works normally and there's no obvious light in the engine bay. I will take another look though in case I have missed one!
I can't work this one out for myself and I don't particularly want to take it along to the auto electrician. Last time I did that it came back with a dent in the bonnet :-(

stratos

i am going to assume the battery and charge system are ok. So we are talking about a a parasitic drain. or something using power though the car is off. if this is the case it's reasonably easy to find.

I used this procedure on a mercedes of 01 vintage but it should translate to the Saab. The car would dain a battery in about 36 hours. All sort of diagnostic tests were done on canbus units etc to no avail.

So I returned to basics. I used an ammeter. I connected the ammeter by disconnecting the battery positive cable and connecting it to one end of the ammeter the other end of the ammeter was connecto the battery. So current entering the car would flow through the ammeter.

My ammeter was only 2 amp so caution was needed. I wired the ammeter in the boot (where the battery is) but placed the unit in the cabin so I could see it . I closed the doors and locked them using the key not the remote as the light flash current would have destroyed my meter.

The Mercdes has a canbus system where modules go asleep after the car is locked. these started just at 2 amps and slowly dropped off to 500 nmilliamps as the car shut down. There it settled 500 mA too much.

I had left the bonnet open as this is where the fuse board is. I started pulling fuses and observing the meter throught the window. Luckily in my case the meter dropped of with the radio fuse.

I took the radio out and found an after market phone device connected to it to allow call audio through the radio speakers. I removed this device, repeated the test and all is well.

The problem with your Saab may be found the same way. hope this helps.

b.c

Have the same problem with my 900 also, changed battery 3 times, new alternator and problem is still there
It does have a hands free kit so ill have a look at that.
cheers