I have a 1994 E-350, 7.5L

There's a parasitic current draw of 3.12 amps. It already killed one battery and I need to find the problem before I kill another.

I systematically pulled each fuse (PITA) and the draw is still there. My only guess is a problem with the alternator, but it's cranking out 14 volts and seems normal.

Any ideas?

Thanks fellas.

 

Yes, it could be a problem with the alternator. A diode could be bad, allowing a leak.

I suggest starting with a fully charged battery, then disconnect the alternator (engine OFF). Now measure for current again.

When you say each fuse, do you mean the ones in the PDC too, or just the ones in the fuse box inside the cab?

 

Dashboard light dimmer/headlight switch. It has a potentiometer designed by Edison that can get shorted to its chassis. This is what was killing my battery on my 2000e150.

 

I disconnected the positive ring lug from the alternator, and no change in draw; still 3+ amps. I can't figure out how to remove the other two wire connectors at the alternator, but I imagine they wouldn't influence anything?

All of the fuses at the power distribution box by the brake master cylinder, as well as all the fuses at the box above the driver's footwell.

 

Thanks! Any way to test it without removing it and taking apart the dash?

Just curious, but wouldn't pulling the fuse for that circuit remove the draw from a shorted dimmer?

 

Hmmm. Not sure about the alternator on that year, but there has to be a way to get those wires off, somewhere. You really need to eliminate that possibility.

I'm looking at the wiring diagram for my 96, and I have three wires: the Big Red One, a light green/ red one (LG/R), and a yellow/white (Y/W). The Y/W should be hot all the time, and goes to the engine compartment fuse box. Internally, it connects to The Big Red One and to the regulator. Mr. LG/R goes to the dashboard charge indicator. It comes out of the regulator.

I think the possibility exists for either of those two to be your culprit. At the very least, you need to eliminate the possibility.

 

Yes, it would, so I don't think this is your problem, because you have checked all the fuses.

By the way, how are you measuring the current draw?

 

I'm using a 22 year old multimeter between the negative cable and negative post on a fully charged, brand new battery at about 12.8 volts IIRC.

I leave it disconnected from the van, battery on a tender, until I finger this one out.

Another point of interest is this all happened "overnight." Never had a problem, then one morning dead battery, and 3 amps parasitic.

Thanks for your help, by the way...

 

An easy to use DC clamp style ammeter makes these jobs much easier to troubleshoot. Prices have come way down over the last decade. I own two models of the Uni-T brand and find them excellent for DIY use. Below is their model 210E AC/DC clamp meter. You can find it on ebay for $35 or less.

https://www.ebay.com/itm/UNI-T-UT210...UAAOSwj85YNWcH

 

I disconnected all wires from the alternator. No change.
Disconnected the headlight switch/dash dimmer. No change.

Frustration sets in.

Out of ideas. Any help is appreciated.

Thanks

 

Pull all your fuses then install them one by one while ckecking for the draw .

Once you find the leaky circuit then you can hunt it down.

 

Yep. Painful, but it's the next step.

Electrical problems are often like peeling an onion - one layer at a time.

 

I'm not familiar with your year van
but
are there 2 fuse boxes like on my '04?

 

I can understand your frustration. Are you aware that with an amp-clamp you can surround a bundle of wires at one time and read the total current flowing? If everything is supposed to be off and you read current, then you can start to separate wires and read individually. The wire color should tell you which circuit is creating the draw.

 

Power distribution box in the engine compartment? There's also relays in that. I'm wondering if it could be a stuck relay?