Battery drain mistery? Alternator?

[nariusb]

Hi all,
I have a battery drain and it's big enough to lover voltage to below 11v over night for the car not to start.
I performed the bulb test by pulling all the fuses and relays under the hood and rear seat to no result - nothing registered. I do have an aftermarket amp but it's not the culprit.

Could it be shorted diodes in the alternator even though alternator tested OK?


Thanks

[Dave M]

Has the battery been drained recently, or otherwise 'abused' (trunk left open, extremely cold, short trips etc)? Even if you're not certain, it might be worthwhile to get it fully charged (if you already haven't) as vehicle charging systems are not designed to charge bateries, only maintain healthy ones.

I just went through this with a jetta. Tested it at night (12.7V), then again in the am (7-9V). Charged it, no more problems.

Good luck,

Dave

[BillionPa]

with my car i had to put a space heater pointing at the battery to warm it up, otherwise it went from completely charged to not being able to start the car in less than 10 mins.

once it was warm it was able to get charged completely.

[Mas (UK)]

after sitting for a few days while I drove around in my little runabout. So I took the battery out, recharged it overnight and put it back in the car ... only for it to go flat again a few days later. I suspected something was draining it because it can normally keep charge for weeks sitting in the car. Then it came to me. My little BMW torch in the glovebox stopped working a week or so before as its battery has died completely (the bulb's ok). And it was still plugged in it's socket in the glovebox. Took it out and no more drained battery problem. This little bugger was continuously trying to charge and draining the main battery. Might be worth checking yours.

Cheers,

Mas

[nariusb]

My battery is 5 months old, and I had it out and trickle charged but the drain off course is still there.
Can my after market amp draw current through the ground wire with positive disconnected, since that's how I had it when testing for draw?

And I'm still curious about the shorted diodes in alternator causing this.

[nariusb]

I pulled alternator today and the draw still the same. One good thing from all that I changed voltage regulator while I had it out.

I also completely disconnected my amplifier and head unit - still the draw was there.

So to sum up I pulled all the fuses and relays, disconnected my stereo system also alternator. It must be a short somewhere but why the fuses wouldn't find it?

[BillionPa]

how many mA is the draw?

[nariusb]

I had my multimeter setup on 10A and it blew a fuse. The test bulb is quite bright indicating much bigger draw then reg. 30-100 mA. When I turn the inside light ON the test bulb gets even brighter.

I do need to invest in a good Fluke DMM I guess.

[nariusb]

I redid the fuse pull one by one and did notice a slight but noticeable draw by fuse #22 ( Windshield wiper Cotrol (ADV), I pulled it and my windshield wipers/spray are functioning.
What could this be caused by?

I'll get the good multimeter and recheck exactly how much mA the difference is.

[nariusb]

I've got the amperage. With all fuses in it draws 0.18A and with fuse 22 removed it drops to 0.02.
Is 0.02 normal?
Where do I look for a short, guys, please help.

[BillionPa]

whats the year and model of the car?

[Karl]

Now you're getting somewhere. Yes, 20ma (0.02 amp) is OK.
Did you mean to say that the wipers will function even with the fuse pulled? I wonder if someone dropped a screw into the bottom of your fuse box?

[naimesl]

Hello,

You might want to check your trunk lock solenoid. At one point I was experiences they exact same battery drain problem and it turned out my trunk lock solenoid was stuck in the open position and was draining the battery.

Good Luck!

Jeremy


Hi all,
I have a battery drain and it's big enough to lover voltage to below 11v over night for the car not to start.
I performed the bulb test by pulling all the fuses and relays under the hood and rear seat to no result - nothing registered. I do have an aftermarket amp but it's not the culprit.

Could it be shorted diodes in the alternator even though alternator tested OK?


Thanks

[nariusb]

it's 1989 525i, Billion

[BillionPa]

fuse 22 is for the windshield wiper pressure controller, which should only draw current when the car is moving. it should also not exist in your car....

the relay could be shot and need replacement, might as well yank it and take it apart.

its in the rear power box at the very bottom left corner. if you dont have one there, do not put the fuse back in, as there is something somewhere wrong.

[nariusb]

You right - my car doesn't have a wiper pressure control and neither has a relay in the rear box, so the short in this circuit is a real mistery. I have the fuse out at the moment and it seem to solve the drain issue.

One more question, do you know if our cars would continue to run if a negative battery cable is dissconected? Apperantly that's one of the altenator troubleshooting methods but I'm not sure. My car just died instantly when I did that.

Thanks again.

[BillionPa]

well, it should run. there are even battery isolator switches to do that right after the car starts so the alternator doesnt need to charge the battery, resulting in more power!

[bsell]

You right - my car doesn't have a wiper pressure control and neither has a relay in the rear box, so the short in this circuit is a real mistery. I have the fuse out at the moment and it seem to solve the drain issue.

One more question, do you know if our cars would continue to run if a negative battery cable is dissconected? Apperantly that's one of the altenator troubleshooting methods but I'm not sure. My car just died instantly when I did that.

Thanks again.

Pulling the battery out of the charging circuit leads to the altenator running without it's dampner, causing voltage spikes approaching 20V! That is almost double the voltage the car's computers were designed to run on. Not a good idea.

Now, your car stopped running when you pulled the battery cable off... I assume once the cable was reinstalled, the car ran fine. If so, the alternator/regulator did not maintain voltage or shut down due to overvoltage (highly unlikely). So I would hazard the guess that your alternator/voltage regulator needs some looking into. I assume that you have some charging system symptoms?...

[nariusb]

Yes, The alternator charges battery, but NO it doesn't go far past 14V when idle only when I rev the engine it temporarily blips past 14V and goes down below that. It might be because it tries to keep up the the charging. Also I did have my mechanic check alternator with Montronics reader and it checked out OK.

Could it be a shorted diode that's undetectable by a fault reader? I changed the voltage regulator already.

[nariusb]

After the battery disconnect while running - the car died. I restarted but it kind of chocked on me and I couldn't get it going for some time with numerous tries and pauses. It runs great now though and the battery kept voltage above 12V overnight this time.



Yes, The alternator charges battery, but NO it doesn't go far past 14V when idle only when I rev the engine it temporarily blips past 14V and goes down below that. It might be because it tries to keep up the the charging. Also I did have my mechanic check alternator with Montronics reader and it checked out OK.

Could it be a shorted diode that's undetectable by a fault reader? I changed the voltage regulator already.

[BillionPa]

throw the batt on a trickle charger overnight.

[nariusb]

Ok, my battery is charging at 2A overnight.
You said that car should run after negative battery wire is disconected so would that mean that my battery isolator switches are failing ir mine dies? If so where do I look for them?


throw the batt on a trickle charger overnight.

[BillionPa]

you do NOT have isolator switches, thats an aftermarket racing product. its designed so you can take the battery out of the charge system right after starting so you have more horsepower.

the transistorized electronics in the alternator should be able to keep up with the current drop from removing the battery from the system, as they are easily able to keep up when you turn off the low beams!

double check the electrical grounds in the engine bay, and make sure the bolt a the B+ junction box is tight and there is no corrosion down there.

[nariusb]

Ground cable looks tight and no rust anywhere. Trickle charged battery is holding overnight at 12.4 -sweet. So it looks good so far with the problem fuse pulled. Thanks Billion



you do NOT have isolator switches, thats an aftermarket racing product. its designed so you can take the battery out of the charge system right after starting so you have more horsepower.

the transistorized electronics in the alternator should be able to keep up with the current drop from removing the battery from the system, as they are easily able to keep up when you turn off the low beams!

double check the electrical grounds in the engine bay, and make sure the bolt a the B+ junction box is tight and there is no corrosion down there.