Still chasing a battery drain

zhenya · Post by **zhenya** » 29 Sep 2009, 11:30

As long as I've had this car ('97 855 T5) the battery has never lasted more than a week, two at the absolute most. This is a problem for me because I travel for work, and often leave the car at the airport for long periods of time. So far, I have replaced the battery and wired the cigarette lighter to allow me to use a solar trickle charger. This has allowed me to get nearly 3 weeks before the battery was dead, at least until recently.

Last week I parked the car for 2 days and came back to a dead battery. I jumped the car, drove it 20 minutes home, parked it, and later that day it was dead again. I finally charged it overnight, and it has been working ok, but I haven't left it yet for more than 36 hours.

Today I did some more troubleshooting. I hooked up a meter in line with the negative terminal and measured current. The car is drawing 100mA at all times, even after having let it sit for hours. I next pulled each fuse one at a time. The only one that changed anything was the radio fuse which dropped the draw to 80mA. Finally, I disconnected the alternator and the draw dropped to 25mA (with the radio fuse in)! This leads me to believe that the alternator is perhaps at fault? I believe the diode bridge in the alternator is supposed to prevent small current drain through the alternator. Is this correct? At this point I'm leaning towards replacing the alternator, but I'd like to do my best to make sure I'm not overlooking anything before spending money on a new part.

My theory also goes that perhaps the alternator is not working all that great, and because the vast majority of my trips in this car are under 10 minutes, that it is not fully charging the battery between starts. If the battery was low to begin with when I parked it last week (from the alternator not ever fully charging it) that could explain why it died in two days, and why it is now working ok again temporarily after a full charge.

Thoughts?

Post by **Ozark Lee** » 29 Sep 2009, 12:19

I would be inclined to buy a new regulator for it. For some reason the 850 regulators are insanely expensive (around $150.00) but they are still cheaper than a rebuilt alternator.

...Lee

FCPEURO · Post by **FCPEURO** » 29 Sep 2009, 12:32

Deffinity either change that alternator or at least the regulator. You can find the alternator here.

zhenya · Post by **zhenya** » 29 Sep 2009, 12:57

Thanks Lee. Can you explain how the regulator works in the chain and why you'd suggest replacing that before the alternator?

Post by **Ozark Lee** » 29 Sep 2009, 13:17

The regulator is actually built into the alternator. It has the diodes, handles the excitation, and the brushes are even built into it. The rest of the stuff in the alternator is fairly bullet proof so long as the bearings are good. The regulators can be a bit hard to find and you will need to get the number off of the alternator to make sure you are getting the right thing.

Based on your description of your problem just changing regulator will fix it.

...Lee

zhenya · Post by **zhenya** » 29 Sep 2009, 13:32

Great. Thanks Lee. I'll see if I can find a regulator or perhaps if I find an alternator cheap enough I'll just replace the entire unit.

FCP, I wouldn't normally call you out like this, but I'm not going to consider buying anything else from you guys until I get my $100 back from the strut mount recall. You won't send me the money until I return the old mounts, and were supposed to include a return shipping label. One was not included, and I've called you guys twice over the past two months asking to have a label sent and still seen nothing.

Post by **Ozark Lee** » 29 Sep 2009, 16:59

If you have any trouble at all with FCP just call and talk to Nick directly. He makes things happen.

...Lee