battery keeps going dead how do i fine the cause?

[78fordf150ranger]

Okay if I charge the battery completely and then leave it over night the battery will be dead how do I go about find the cause

[Tacoclaw]

The quick way it to pull each fuse I your fusebox, and see which ones spark when the key is off. Find out what circuits they protect, and that's the circuit your problem is typically on.

[78fordf150ranger]

Okay I'll give it a try. I noticed that if the charger is hooked up charging the gauge will drop every now and again and the jump back up....I guess pull fuses and try a test light?

[Tacoclaw]

I don't think the rest light will be that helpful in finding an amp draw. The first thing to do is just wait until its dark then mess with the fuses. The darkness will make it easy to see it sparking even if it's just a little one. Draining a battery overnight is a pretty nasty draw though, so unless it's a bunch of small ones it should be pretty obvious.

How often does the needle drop happen on the charger? Does the needle drop indicate that it's charging at more amps or less? It may just be a feature to let the battery recover momentarily at high amps or something.

[PToombs]

Remove the negative terminal from thne battery. Put a test light between the battery post and the wire. The test light will light up if there is a draw. It may glow quick and fade out, this is normal, it's the computer and radio memory. If it stays lit, unplug the alternator wires, if it goes out, that's the draw. If not, then start pulling fuses until it goes out. When the light goes out, the draw is in that circuit someplace.
If it doesn't, then you need to dig into what has power with the key off, or look for a shorted wire. Let's not ask for trouble until you check the easy stuff.

[78fordf150ranger]

Okay when I hook a test light up to the disconnected negetive battery cable and jump it accross to the positive cable I get nothing no light up.this a good thing? Now when the truck is running the alt gauge bounces up and down up and down the whole time the truck is running bad altinator?

[PToombs]

No, you did it wrong. Put the light between the negative post on the battery and the negative wire you removed.
It may be the alternator, there have been posts on it before drawing the battery down.

[78fordf150ranger]

Okay the test light lite up and my volt meter said 12.32 volts.I never had this problem till I did my cab swap, I used all the wiring and dash out of the old cab.

[PToombs]

Do you have a glovebox light? It may be adjusted wrong and staying on. I had one that stuck on all the time, I about pulled my hair out until I happend to be in the cab one night and saw a glow under the dash. I was like, wtf? Open the glove box and grab the bulb right away, if it's hot, it was already on.

[78fordf150ranger]

I'll check. Now I pulled all the fuse one at a time with the volt meter hooked up to the disconnected ground and then to the NEG battery post and the voltage never when to zero, now when I remove the big black wire going to the fuseable links the volt meter gose to zero.

Is a 91.5 fuseable link break down the same as a 1993 dodge reg cab long box 4x4 auto

[PToombs]

So the draw is down the wires fed by the fusable links for sure.

I'm not sure about that.

[78fordf150ranger]

Any idea what the fuseable wires feed?

[PToombs]

Looking in my '93 FSM, a white wire feeds the #13 fuse for the hazard flasher, the gray feeds the #4, 5 and 6 fuses, another gray feeds #15 fuse and 2 reds feed the ignition switch. The colors are the wires before the fusable link. There may be more, that was on the 1st 3 pages.

[78fordf150ranger]

When you say before the chewable link do you mean towards the battery or the fuse panel under the dash

[PToombs]

Towards the battery. Ellis posted schematics for a 90 truck, I saw it yesterday. It may be the same as what I ahve, but you could print it off and have your own copy. It would be easier to work with that way.