I have a 1989 B250 and I'm trying to track down the a slow battery drainage problem I have. I'm using the method of connecting a multimeter to an unattached positive terminal and the negative cable and reading the amps, while pulling fuses to see which circuit is draining the battery. I'm going to try this tomrrow, but my question is, once I narrow it down to which fuse is causing the drain, how to I narrow it down to which specific device is draining the battery? Do I have to pull the fuse box out and read every wire? Any tips for an easier way of doing this?

Thanks,
Michael

 

Rather than connect to the battery and cable, just pull the fuse and put one meter lead on each fuse terminal. Same result, but at least you won't be going back and forth from the fuse box to under the hood. Once we know which fuse number is the problem we can help a lot more in pinpointing the problem.

Do you have a glove box or underhood light? If so make sure it's not staying on even when the glove box door/hood is closed. I've seen that problem of a hidden light bulb draining a battery more than once. Trunk lights too, but that not an issue with vans. Brake lights are another culprit if the brake peddle linkage is worn, causing the peddle to rest on the switch and make contact. Alarm systems and radios will kill a battery within a few days if the battery is old and on it's way out.

 

I'm hoping this is a typo, or else you're going to blow that meter up right in your hand. Voltage readings are made parallel to the power source, amps are read in series. If your meter is set to amps and you connect across positive and negative, it will be a dead short. If you're going to use this method, take the negative cable off of the battery and put one meter lead on the negative post and the other meter lead on the negative cable. Always use the negative battery lead, in case something shorts to the body, you won't end up with a positive to negative short.

 

Instead of doing that, why dont you eliminate the fuses first. rather than asuming that the drain is on a fuse, verify that it is. Pull all of the fuses and see if the issue still exists. If it does, checking any of the fused areas wont help you. Also every time I've had a 'draning' problem it has turned out to be the charging system not working properly. Most notably are bad diodes in the alternator,or a bad voltage regulartor.

 

Just got done checking the first 4 fuses untilI cracked one and decided to call it a day (what is the best method for pulling these things?) Fuse 3 that has the Clock and the Radio was pulling 12.25 volts, which sounded a little excessive to me. The CD player keeps skipping and cutting out channels on me so I'm going to replace it within the week anyways, but how much voltage is normal for a radio with no key in the ignition? -Michael

 

It's supposed to have around 12 volts. You concern is not with volts, but amps. Pull the fuse and take an amp reading across the two fuse terminals for that circuit. That will tell you the power draw.

 

Yep, you're looking for amps, not voltage. With everything off, you should have no more than a couple hundred milliamps being drawm from the battery. If this draw is considerably larger, then something is drawing too much current. If it is OK, then you have a bad charging system (like IGadget mentioned).

 

I'm havinga bit of trouble getting a good reading from my multimeter. Regardless of what setting I set it to, (2m, 20m, 200m, 10A)I get a reading of either .3, .03, or .003. When I sent it to 200 mA I get a reading of .3 (.3 milliamps? Am I reading that right?) I don't get any reading on with the positive lead plugged in to the mA plug, and can only get a reading plugged into the 10A (unfused) socket. Is my meter busted? If I blew a fuse it wouldn't turn on at all, right? It reads voltages from the battery just fine.

 

How and where are you connecting the black and red leads?

 

All of the values equal the same thing, and yes that is .3 miliamps. or .0003 amps
when checking AMPS though start at the highest setting and work your way down. this way you are less likely to blow up the meter.

Make sure you are checking DC amps and not AC amps.

What do you get on the meter if nothing is connnected? It should be zero when reading amps. If it isn't zero then your meter is off calibration by that value.