bad luck tonight. i have been having trouble with my 96 855T holding a charge in the battery (which is fairly new). If I drive it every day, it's about 90% sure to start, but if not driven daily, it's about 90% sure to go completely dead. So this morning (after jumping it), I drove it to a friends house and left it there all day. Got back at night and it was dead. Jumped it and started right up for about 30 seconds then went completely dead.

Here's where the big snafu happens - I tried jumping it again, but in the dark, I swapped poles on the battery by accident and STUPIDLY left them on there for about 10 seconds until I figured out what was going on! The cables were so hot, but after I corrected the poles, I managed to get it going for a moment, then it stalled and would not turn over after that at all. I could only crank it with jumpers, but no start.

Anyone want to take a stab at how badly I've buggered this thing up? What are my best and worst case scenarios?

thanks,

scott k

I think by reversing the jumper cables you might have damaged or at least fully discharged the battery but not likely more than this. The alternator diodes would not be damaged except by a very severe overvoltage, much more than a 2nd battery could provide, no matter how connected.

I agree the glove box light is probably your original problem. Check for any OBD codes. They will probably give you a good clue.

Thanks for the input. The only dash light that came on was the SRS light. Can that light be reset by a tech?

Scott,


How many miles does your '96 have on it right now?

When I first got my '96 850 last year I had the same problem you had. Except I replaced the battery (which was original), and then everything went fine.

I have '98K miles on it - replaced the battery Nov '05 which helped for a while until the glovebox light (or something) must have started draining it again, and then the problem started happening again. Obviously operator error!

If I damaged the ECU can I replace it with a used one? What kind of match do I need? (ie. - year/engine model?) I'm selling this thing, so I don't want to sink a bunch of $$ into it.


sk

You are havin' a rough day! The minimum damage you do by reversing polarity on a jump start is ruin the diodes in the alternator. There are also a number of fused links that can blow. What if anything happens to the ECU I don't know.

On your dead battery, a common 850 problem is the glove box door switch that allows the light in there to stay on and drains the batt. That's easy to fix if a problem. I start with the basic troubleshooting triad. If you have fuel, fire and compression, they have to run. Odds are it's ignition (fire). Look in the 700-900 FAQ section on RWD. There is a logical sequence to track down a no start condition that applies to all engines. Good luck!

bl