Car Battery Being Drained

HAWAIISSON

MEMBER
1991 FORD RANGER

Electrical problem
1991 Ford Ranger 6 cyl Two Wheel Drive Automatic

I bought a new battery due to battery drainage. Truck runs fine but after sitting for a few days the new battery is drained of power. What is causing this to happen. I have nothing but stock components and have not altered this truck in any way. I have already paid for a new alternator as I thought this was the problem initially. After jumping battery, truck run fine until sitting for 2-4 days. HELP.

Friday, May 23rd, 2008 AT 6:33 PM

3 Replies

LEGITIMATE007

MECHANIC
5,121 POSTS

Get an analog voltmeter remove the negative battery cable, attach the Black lead to the battery post, Red lead to cable end, then pull fuses one at a time, make sure there are no accessories or lights in the on position, Key off! Close the door after each fuse and check meter, when you pull the fuse for the bad curcuit, the meter will drop to 1 volt or so. Check all fuses, even under the hood. If meter does not drop, remove the battery connection from the alternator, if it drops now, the diodes are bad in the alternator. Put the fuse back in were it goes as you go so you don't forget which fuse goes were! This will find out what has the Parasitic drain condition.

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Friday, May 23rd, 2008 AT 10:58 PM

ROBLEWIS

MEMBER
17 POSTS

Similar problem here (1991 Ranger 4.0L). An ammeter on the battery shows 2.4 amp draw with everything off. If I pull the 15A "underhood lamp" fuse in the power distribution box (near the battery), the draw drops to 0.01 amps, probably negligible. BUT if I then start the truck, the "charge warning" icon (little red battery on the instrument panel) comes on. Reinstall the fuse, and the charge warning goes off but the parasitic draw comes back.
The manual implies that the only circuit affected by this fuse is the underhood lamp, but this apparently isn't the case.

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Sunday, May 11th, 2025 AT 2:41 PM