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I have an '88 900 which is in very nice shape. One big problem: the battery dies every 3-4 weeks. Not just drained, but to the point where it won't even hold a recharge. I've been through 6 batteries this year (fortunately the people at Napa are GREAT about their batttery warranty!). It also isn't a gradual thing ... the car starts and runs fine right up until it dies.

I have had my mechanic at British Motors (the mechanic is British, but he only does Saab work) look at it a couple of times; the alternator checked out OK and he also thought it might have been a problem with how the battery was grounded, but that didn't make a difference.

Any ideas? Thanks!
 

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What electronics are in the car - alarm? Aftermarket radio? SUBS.... anything like that could cause a draw - even a light in the trunk could drain your battery over nite. I'd start checking those simple things first - as well as your cables - both ends - follow them to see if there is a short/ground - anything which cold be deemed as a parasidic load. Any corrosion on your terminals? That would do it too. I would imagine it's the alternator but you said it checked out ok. Sounds like an alternator issue to me.... but that's my advise for now without seeing the car. Good Luck - keep us posted.
 

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burnsside is on the right track with something drawing power, but I think you also need to check this out with a multi meter while the car is off. if it's drawing more than say .02 amps while the car is off, it's too much. also make sure that your batterys heat sheild is in place and that you are not under rating your battery. the C-900 needs something like 650 CCA's. if you bought a 400 CCA battery it would start the car but only for a few months!
 

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make shure the battery has enough distilled water in it there is ususlly a little indicator that changes color when there is not enough.
 

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You could install a cheap voltmeter from the positive of the battery to ground, temporarily. Put it in the ash tray for a week or two. It would be on all the time. They are a high resistance item and don't use much current. Since the problem is sporadic, you could check the voltage of the battery every time you turn the car off. Then checking for things like funny ignition switches, stuck light actuators, etc could be done when the cause is drawing voltage.
 

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Does the car have automatic seatbelts? They can be a common place for a draw to occur. Also the ignition switch can become shorted out internally and cause a dead battery, but that will usually happen rather quickly, over only a day or two.
 

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i had this problem with my t16s / spg ,someone had cut the wires for the stereo and the live was grounding and draining the battery , just a thought
 

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1981 8v c900 sedan, 1990 2.0 9k carlsson, 1992 21 c900 sedan
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pjriowa said:
I have an '88 900 which is in very nice shape. One big problem: the battery dies every 3-4 weeks. Not just drained, but to the point where it won't even hold a recharge. I've been through 6 batteries this year (fortunately the people at Napa are GREAT about their batttery warranty!). It also isn't a gradual thing ... the car starts and runs fine right up until it dies.

I have had my mechanic at British Motors (the mechanic is British, but he only does Saab work) look at it a couple of times; the alternator checked out OK and he also thought it might have been a problem with how the battery was grounded, but that didn't make a difference.
That is not a good situation to be in. I've had one battery fail in the last year but I'm not sure why yet. The new one I put in about 3 months ago is fine at the moment.

I did all the usual checks to make sure the alternator is working, and I even checked the parasitic drain with the ignition off and the key removed. All within spec.

However, what I did notice was that as soon as the key is moved from 'accessory' where about 1 amp was being drawn according to my meter, to 'run' where the fuel pump is enabled, the current drain shot up to almost 12 amps. So the fuel pump, on it's own, is pulling over 10 amps and on a nomimal 12 volt system that is around 120 watts of power draining out of the battery! It's similar actually to the power drain that headlights give if they're on without the engine running.

Anyway, before you panic too much, have a look at this url from the Swedish Wrench website:

http://www.swedishwrench.com/battery.htm

and see if any of that helps you diagnose what might be wrong.

One thing I haven't seen covered in many places is voltage regulators that might not be properly regulating the alternator output. I've suspected the voltage regulator in my car's alternator for some time as outputting DC with a sizable AC component (remembering that the alternator is an AC device with a series of diodes to direct current the right way to give unregulated positive-going output that's fed into the voltage regulator), though I need to remove a lot of things to get to it. Might try pulling out the alternator next time I have a few rostered days off work in one stint. :cool:

The DC voltage as measured by my meter always hovers between 12.8 and 13.7 volts when the engine is running so that tells me the alternator is producing DC output, however the voltage output should be higher (between 13 and a little over 14 volts), and that's what's making me suspect the voltage regulator and/or the brushes as well. I'm not sure if there is an easy way to connect the meter to measure AC and block the DC part of the alternator's output. The battery itself is an absorber of 'ripple' that might be present, but I don't know how much a normal lead-acid car battery can take before it begins to have problems such as collapsing cells, etc.

I'll need to pull the alternator to check all this out. I'm looking at trying one of the external voltage regulators from Group9 and seeing how that goes, along with a new set of brushes.

Craig.
 
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