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Battery drain

I have a 1992 Dodge Dakota that I use rarely and have a problem with something that is draining the battery. I have tried putting a meter on the battery and pulling the fuses one at a time but can’t seem to find the problem, Any suggestions?

Did you use a voltmeter or an ammeter? Either should work on a '92 Dakota as you don’t have a lot of computers and other semiconductors in there that have to stay powered all the time.

With a volt meter, you will see full battery voltage between the battery terminal and its cable if there is a drain. With an ammeter, anything over about 50 mA for longer than 5 minutes or so after connecting the meter is generally considered to be a problem.

First place to look for drains is add-on accessories - alarms, CD changers, amplifiers, etc. Drains in such accessories may be normal, such that you have to disconnect them if you are parking the vehicle for an extended period. My daughter has to disconnect the CD changer in her trunk if she is parking the car for more than 2-3 weeks.

Then check courtesy lights under hood, in glove box, etc. to make sure they are turning off. One leak that will not go away with the fuse pulling exercise is a failing diode in the alternator.

I used a voltmeter and could see a drop in voltage slowly. After leaving the truck parked 2-3 week I would find the battery dead, I don’t have any add-ons other that the radio. How would I check the alternator to see if that is the problem?

By disconnecting the wiring to the alternator it will eliminate it from the circuit. If you do this remember the main lead is hot to the battery so diconnect the negative lead of the battery first before you work on it. Make sure that lead doesn’t touch anything if you remove it and reconnect the battery. The alternator may be trouble but it is doubtful.

Here is a link to show you how to find this kind of trouble.

used a voltmeter

Use an ammeter. Voltage is potential power. Amps measures actual power.

Thanks, I’ll try the link too

If you drive this truck rarely why don’t you just put in a battery cut-off switch ? You would just have to open the hood and turn either a knob or a lever to drive it .

Yes, I have discussed this option with my mechanic. That might be the way to go if I can’t find the problem

The Problem Could Be A Faulty Gauge Or Transistor In The Dashboard Intrument Cluster Or Overhead Information Center (If Equipped).

Don’t make any moves be they modifications or parts purchases until a proper parasitic draw test is performed.

Contrary to much automotive lore these are not very hard to find,your truck should be the mechanics proverbial “piece of cake”.

Just to clarify, when you check for a drain, are you disconnecting the battery negative lead and putting the meter in series between the battery and the lead?

With a voltmeter, you will see full battery voltage if there is a drain. Anything less than full battery voltage (e.g. 10 volts) means the problem is not a drain. Voltmeter works only on older cars that don’t have always-on computers. I am not sure about a '92 Dakota, best to use an Ammeter.

Using an ammeter is a lot harder because

  1. an inductive ammeter will not likely be sensitive enough to measure a 3-week drain, and a series ammeter may not carry enough current to carry the full drain without overloading.
  2. When you disconnect the battery cables and then re-establish a connection through the ammeter, all the computers ‘wake up’ and you have to wait until they all go back into hibernation before you can check for drain. Time to hibernation varies by vehicle. The way to avoid waking up the computers involves making the ammeter connection, and not breaking that connection as you disconnect the battery cable. This takes about three hands and a lot of finesse.

It did have a tachometer that was not working when I bought the truck. I replaced that and did not have a problem for abbout two years. There may be something else to look at there. This truck came with the problem.