Auto mags- help me diagnose an electrical problem.

[flatNshallow]

04 Montana van, parked it for a couple months without starting, Battery dead. Charged it and it started but 2 or 3 days later, dead. Had battery tested, was bad, replaced. A couple days later, dead. Basically it'll hold enough of a charge to start after sitting for 1, maybe 2 days, reset if driven or allowed to run / recharge. But if it sits more than a couple days, it dies. If driven every day it's fine, but I want to sell it and don't feel right about hiding this issue.

Obviously something is drawing current all the time... but what and how to repair?

Ive done the obvious and made sure all accessories are off even turned off all interior lights with the “all off" override switch... the only electrical system that is showing any issues is the power sliding doors which sometimes will latch properly and reopen our fail to release latch and thus fail to open. No sound of a motor running...

[Todd Zander]

Was the alternator tested? Whats it putting out for charging voltage under load? You could very well have been running off the alternator and it popped a diode or the regulator inside.

[flatNshallow]

Todd, I'll look into that but it does not explain why it goes dead just sitting after a full charge...

[Vt-Freeheel]

Try pulling the fuse for the power doors and see if the problem goes way. There may be a solenoid involved that is bad.

[ill-advised strategy]

The other thing to do is pull fuses one by one while continuously monitoring battery voltage with a digital multimeter...find what circuit is drawing and zero in from there.

[RobertRS]

Connect a meter that will read current in between the battery terminal and the cable you removed. You will no doubt have a reading, which indicates current draw. As was suggested above remove fuses one at a time, looking for the one that reduces dramatically the current draw. Somewhere in that circuit will be the reason for the excessive draw. Old cars prior to computers in cars would have no current draw, modern ones do have a draw to power the computer but usually it takes quite a while (over a month) for the battery to go down

[Cocximus]

You can also pull the fuse and connect an ampmeter between the fuse connectors. Basically make your ampmeter the fuse.

Just a FYI if you use a clamp-on amp meter on your battery leads note that most clamp-ons don't do DC.

[RShea]

I'd also vote for a short or some sort of device pulling volts all the time. I had a electric antenna motor draining my battery either due to a short or motor and finally had it diagnosed and pulled the fuse with the antenna in the up position.

[SB]

My dad had a shorted cable on the main wire harness for his truck years ago, insulation had become worn off and had direct contact with frame. Several shops were not able to find problem until he took it to dealer and they kept it till they found the issue.

[Todd Zander]

A bad voltage regulator can drain the battery.

[Harry]

The other thing to do is pull fuses one by one while continuously monitoring battery voltage with a digital multimeter...find what circuit is drawing and zero in from there.

^^THIS ^^

[flatNshallow]

The other thing to do is pull fuses one by one while continuously monitoring battery voltage with a digital multimeter...find what circuit is drawing and zero in from there.

I'm electrically challenged... how does one monitor battery voltage with the multimeter? Where am I connecting the process? Directly to the battery or across the fuse contacts?

[Todd Zander]

On the battery posts. Ideally stick them in so your hands are free. With the car off, watch the battery voltage for a few mins, it will be somewhere in the 12's, if its steadily dropping by the hundredths then disconnect the cables and watch it again.

[flatNshallow]

A bad voltage regulator can drain the battery.

Interesting, more detail please.

[flatNshallow]

On the battery posts. Ideally stick them in so your hands are free. With the car off, watch the battery voltage for a few mins, it will be somewhere in the 12's, if its steadily dropping by the hundredths then disconnect the cables and watch it again.

So I should see a very slow drop which should remain constant until I pull the offending fuse at which point the drop should stop or get very very slow?

[ill-advised strategy]

So I should see a very slow drop which should remain constant until I pull the offending fuse at which point the drop should stop or get very very slow?

Let's say your friend has the multi meter on the battery and it says 13.59....most fuses you pull shouldn't change that reading...when you pull one and it goes to 14.10 (or whatever) you know that's a circuit drawing power. Then you have to look into why/ how it's drawing power with the key off. That's probably more of a simplistic old-car thing to do....but if you do it and find something easy you can just deal with it yourself.

[Touring_Sedan]

04 Montana van, parked it for a couple months without starting, Battery dead. Charged it and it started but 2 or 3 days later, dead. Had battery tested, was bad, replaced. A couple days later, dead. Basically it'll hold enough of a charge to start after sitting for 1, maybe 2 days, reset if driven or allowed to run / recharge. But if it sits more than a couple days, it dies. If driven every day it's fine, but I want to sell it and don't feel right about hiding this issue.

Obviously something is drawing current all the time... but what and how to repair?

Ive done the obvious and made sure all accessories are off even turned off all interior lights with the “all off" override switch... the only electrical system that is showing any issues is the power sliding doors which sometimes will latch properly and reopen our fail to release latch and thus fail to open. No sound of a motor running...

I'm betting that the rear air suspension is leaking and the compressor is attempting to keep it inflated.

[robgoose]

my temporary solution to this pro ken used to be disconnecting the battery when I'd park my car (but it had its downsides) and I agree that you should solve the problem before selling.

[Cocximus]

^ baterry voltage without the motor on should be 12 something. With the motor on it should be ~14. You want to test with the motor off.

Testing for voltage might be unreliable. Depending on draw it might be hard to catch V fluctuations. You should really try to test with an ampmeter.

[flatNshallow]

^ baterry voltage without the motor on should be 12 something. With the motor on it should be ~14. You want to test with the motor off.

Testing for voltage might be unreliable. Depending on draw it might be hard to catch V fluctuations. You should really try to test with an ampmeter.

Any procedural differences from what yeti gave for voltage based testing? Or just different units, criteria etc? Ie, what would I be looking for with an amp meter?

[Todd Zander]

Any procedural differences from what yeti gave for voltage based testing? Or just different units, criteria etc? Ie, what would I be looking for with an amp meter?

The irony here is it's much easier to diagnose a voltage drain with a voltmeter on a bad battery lol.

The difference between using a multimeter and ampmeter is what they measure. If it's a small amp draw the voltage might not drop very fast which would not show up easily on a voltmeter. However an amp meter, which I believe is used inline on the positive battery cable, is more accurately able to show you if the battery is currently powering any device( ie it's drawing current measured in amps) with the key off.

I still stick to my original post that the regulator is at fault after essentially powering the car for a couple days with little to no help from the battery. Find a electric motor repair shop or alt/starter rebuild shop and have them bench test it. They should be able to determine if the regulator is bad, causing the alternator to draw current through the internals while the ignition is off.

[ill-advised strategy]

As with most automotive things, I'm living in the 80s and I'm completely overmatched with the modern world.



Standard tgr precautions apply. Don't take any advice from some random idiot on here. Today that's me.

God, I miss my 1978 F250. I feel like the way the world has engineered simple automotive maintenance and repair away from the layman is a form of evil. Honestly.

[Cocximus]

Any procedural differences from what yeti gave for voltage based testing? Or just different units, criteria etc? Ie, what would I be looking for with an amp meter?

Basically you need the amp meter in series in the circuit. Volt meters are in parallel. Very different how you use them. The video yetti posted looks pretty good... but I really don't have the patience to watch it.

[RobertRS]

There was a good suggestion a few post up, that is do you have a big box auto parts store in your hood? If so get your vehicle down there and let them test your charging system which they do for free. That would be a start. If that is not do-able you are back to the amp meter. I am guessing you do not own a VOM (volt, ohm meter) so find a friend that does. The owner should know how to work one. The amp setting is the function of the VOM you are going to use. You will need to disconnect one of the battery cables and the meter leads go to those two points; one one the cable and one where the cable came from. I am guessing the reading will be several amps to kill your battery that fast. The suggestion to remove fuse is a great way to find the circuit that is at fault.

It sounds like you are in over your head on this one and maybe you need to take it to someone to get it fixed?

[flatNshallow]

There was a good suggestion a few post up, that is do you have a big box auto parts store in your hood? If so get your vehicle down there and let them test your charging system which they do for free. That would be a start. If that is not do-able you are back to the amp meter. I am guessing you do not own a VOM (volt, ohm meter) so find a friend that does. The owner should know how to work one. The amp setting is the function of the VOM you are going to use. You will need to disconnect one of the battery cables and the meter leads go to those two points; one one the cable and one where the cable came from. I am guessing the reading will be several amps to kill your battery that fast. The suggestion to remove fuse is a great way to find the circuit that is at fault.

It sounds like you are in over your head on this one and maybe you need to take it to someone to get it fixed?

Probably but I'd have been a fool not to tap the power of the collective.

In any case I won't get to try any of this until I get back state side. The older I get the more I hate business trips.