Phantom battery load

Maintenance/Repairs
1

On my “new” 1989 Dodge B250 camper van, the existing battery died once or twice just after I bought the van, so I just thought it was old, and I got a new battery. New battery worked great…then I parked the van for a week, came back, tried to start it…battery totally dead.

So there’s definitely a phantom load somewhere. Now, I did suspect a phantom load when the old battery died. The van’s wiring has been modified by previous owners to allow the engine battery/alternator to charge two 12V auxiliary batteries in the back of the van. But there’s a manual toggle switch that disables the charging circuit, and i left that switch ij the off position. Furthermore, the charging circuit is disabled with the ignition switch in the off position. I verified this with the old battery before replacing it.

So I convinced myself that the charging circuit was not the source of the drain, and that the existing battery must have just been old.

But, now with the new battery totally dead, obviously there is still a phantom load.

Question is: what are the possible sources of the drain, and how do I go about tracking it down?

2

PS…one more piece of data…after I tried to start the van today and found the battery dead, I hooked up my Electromate 400 and tried to jump start it. I was so aggravated that I didn’t pay attention the the LED light on the Electromate that indicates the condition of the alternator. Now that I think of it, I’m pretty sure that LED was red…which according to the Electromate manual means the alternator is bad. A good alternator should cause a green LED to show up.

So…what does the red LED really indicate? A bad diode in the alternator…which could be the phantom drain?

Also, is it possible that an alternator can still put out a good charge even with a bad diode? Because the van has a good voltmeter, and the alternator has been putting out 13.5 volts or so on the highway according to that meter.

3

Place a multimeter in line between the battery and the vehicle harness set to Current. What value is seen? Then start removing fuses one by one until that value drops to milli amps range. Then chase the circuit from the fuse box name.

4

Or, is it possible that the red Elecromate LED is indicating a short circuit through the phantom load, and not through a bad alternator diode?

W30, I did try to get a current reading with a digital multimeter, but couldn’t get any reading, not even in the milliamp range…

5

Oops…forget what I said about the alternator test LED. It reads correctly only with the engine running. And since I couldn’t start the engine, the red LED means nothing. Sorry. Back to square 1.

6
7

Remove the negative battery cable. Place your meter between the cable and the battery post, negative meter lead to negative battery post. To avoid damaging the meter, use the 10 amp scale on the meter. Sometimes you must move the lead to the a separate 10 amp socket…

8

Thanks, Barky, that’s what I was looking for.

9

Thanks, Caddyman. I tried that but got no reading on my meter…just realized the 9V battery in my meter is dying…will try again tomorrow with a good battery in the meter.

10

I am having a problem not too far from what this guy is in 1997 Buick LeSabre Limited (6 cyl).

I really hope someone can tell me what it is.

We bought this LeSabre at Auction, for about 3K. After purchasing, it we put in a new battery because the engine would not start. The car ran for several miles, and we parked it. It would not then start, and we had to jump start it.

Jumping the car caused the Buick to reset all its eletronics, and then everything was going crazy for a few hours until the car’s electronics were reset. We were told this is normal when the power is cut off from the battery.

We had a mechanic inspect the car for various problems occuring with the RPM guage and fuel guage which were going randomly berserk. We then replaced the cluster of the car panel, and that seemed to fix the RPM issue, but the fuel guage was not working still, and the auto mechanic chalked this up to a sensor in the gas tank not working.

We then returned home in the car (not having fixed the fuel guage issue), and the car was driving fine, until it then suddenly had all power cut and died out while driving it. Note, the mechanic had to start the car in order for us to drive it. (It was sitting two weeks.) We then put more gas in the car, and this seemed to solve the problem, for a several hours, but then the car died again, and just lost.

Now the car does not always start, and when it does it randomly loses power power while driving. It must then be placed back into Park and then restarted.

We are curious to know if the car may have been tampered with via the distributor cap somehow, or if there is come other problem with the electrical power. The battery was just bought a month ago, and appears to be good.

Our mechanic says the battery might still be bad even though it is new. Any thoughts on what might be going on here? It acts like a float issue I once had with a Buick, when I would turn corners the float would cut off the power. However, this car is fuel injected, so that can’t be.

Any takers???

11

Hopefully you are placing the meter in series with the battery ground lead. The meter needs to be set to read DC amps and a nomal current draw should be around 20 milliamps if everything is off that is supposed to be. If you still don’t see any current flow then check the protection fuses inside the meter, they may be blown out. Having 13.5 volts is a little on the low side so there could be a bad diode or two. Have a shop do a load test on the charging system.

@ARH
I’m not sure what you mean when you say everything went crazy for a couple of hours. That isn’t normal in my book. There may be some bad diodes inside the alternator that is causing trouble due to high AC ripple voltage. The random loss of power may be due to a bad power wire connection between the battery and the fuse panel under the hood or possibly a faulty ignition switch.

12

@ARH, you should really start a post of your own, and imho you need new spark plug wires and distributor cap and rotor if applicable.

13

I put the recharged battery in this morning, and found a 0.4 amp drain on the battery with the ignition switch off. Started pulling fuses until I got to #8 and then the drain disappeared. It was the circuit with the aftermarket stereo on it…not sure if it was the stereo or something else on that circuit, but I pulled the fuse, so the drain is gone.

14

To avoid damaging the meter if you’re using the 10A scale, also keep in mind that if you place it between the battery and the car’s electrical system, it’s like temporarily replacing the main water line in your house with a soda straw. Don’t turn on any electrical accessories and definitely don’t try to start the vehicle with the meter in place. Only use it for testing the current draw with everything off. Also keep in mind that most meters have a separate place you plug in one or both of the test leads when using the 10A scale. If you use the wrong position or run anything electrical that draws a lot of current, at best you will have a blown fuse inside the meter. At worst, you will toast it.

15

Thanks, oblivion, I was careful to use the 10 amp setting and didn’t turn on any accessories, so my meter survived :slight_smile: