Hokay, here's the vehicle. 1984 Ford F250 XLT, 460 V8, c6 auto, 2wd, yeah. Problem: battery dies over night. Why? No flippin' clue. HELP!

 

OK. Charge your battery. Then, disconnect one cable. Connect a test light between the cable and the battery. See the light glowing? If you do, get in the truck, close the door, or disable the interior lights. Remove each fuse one at a time. When the fuse you remove causes the light at the battery to go out, you are almost there. Depending on the fuse, you could have a switch that is bad, or something else.

If its not fuse issues, you could have a leaky diode in the alternator, among other things. You can remove the alternator from the circuits by disconnecting the fuse link at the solenoid. Best of luck.

If all that I have said is greek to you, then, get a chilton manual, or make friends with an automotive electronics tech.

Again, best of luck!

 

I dont have a test light,so i used a multimeter set to 12 volts. I didnt undo fuses, but i undid alt wiring harness, and bam, 0 volts...i was happy, so i replaced alternator....same thing, 12 volts at the read out, i'll go try that fuse thing now.

 

Well first I would make sure that the battery is not at fault. A shade tree mechanic can test it by Disconecting it from the vehicle when you park overnight, and reconect it in the morning. If it starts up fine then I'd say you have other problems. If it goes dead without it being hooked up, then I'd say change the batt. You can also have your battery tested at a autoparts store. They will put a drain on the battery, and if it discharges way to quick then... etc...



If the battery is good, then you can do this easy, but albeit tedious test.

Remove all the fuses in the fuse panel. Leave it overnight. If the battery is dead, then you have a short in the wires not protected by the fuse panel. Wipers, Ignition, Headlamps, etc...

If the truck starts fine, then add one fuse at a time, each night until the truck goes dead again, then you have isolated the problem in that protected circut etc..

I did say that it was tedious.

Another test you can do but is much more complicated, but less time consuming.
If you have access to a ohmeter, digital would be best, you can hook that up to the battery and measure how much draw the battery is subjected too, sort of like how the amp guage is hooked up in the cluster. You remove all the fuses in the panel with everything switched off in the truck, then you add each fuse back and note how much draw each circut puts on the battery. The one circut that draws power without anything being on is the culprit etc...




Hope this helps.

 

You said it much better than I did.

 

Hokay, I removed all fuses, still read 12 on the multimeter. I disconnected the alternator...0 volts. So i hooked up one of the wires to the alternator, and then it read 12 volts again....I dont understand. It's a brand new alternator.

 

You can measure current in series that way if the meter can handle the load of the particular circuit in question (usually 10 amps is the limit on most cheap meters), but don't meter resistance in a "live" circuit, it can fry the meter.

Meters measure resistance by using their own small battery to supply the voltage. Any voltage you might connect to goes directly into the meter's own circuitry. A car battery will way overpower it and it might fry the meter or at the least blow an internal fuse or part.

Also don't try to read the current directly across the car's battery, which can be 60 amps or more. It'll melt the probe wires in your hands, not to mention the meter! Or in series with your starter, wiper or blower motors, as they draw too many amps for the dinky digital meters to handle.

To measure current, always hook one meter probe to the battery, the other probe goes to a single circuit's wire which you've removed from power. The meter and probes complete the circuit and the current used by the circuit will be displayed on the readout. Measure current in series, in other words.

An easy way to do this is first set the meter to the highest current range. Remove a fuse and put one meter probe where each leg of the fuse went. Turn the key on and turn on whatever circuit you're testing. In your case, since you're really looking for something that draws current with the key off, run your tests with everything off.

Whatever would be normally passing through the fuse will now go through the meter instead. You can check voltage this way, too, but not resistance!- unless you first disconnect the truck's battery.

Reverse the probes if you get a negative reading on an old-style analog meter that has a pointer and scale. If you have a digital meter, it'll just put a minus sign up there or set itself automatically, so polarity isn't a real issue with them. On a cheapie meter, readings may be slightly different with probes one way or the other, ignoring the polarity sign.

There are automotive testers specifically designed to handle high currents. Only they should be used to meter battery or alternator output currents directly.

Zat's all I know, hope it helps!

-Smoky

 

ok...thanks for the info. The meter seems to be holding up thus far:P So correct me if im wrong, the + cable connected to the starter solenoid should not in any way have continuity with the engine block or any chassis ground, oui?

 

I added some to my earlier post in an edit, might help further.

Normally, you will see a little juice being used. Computer memory uses a little. If your radio has a clock or station memory, that's another small drain. Some alternators perhaps do always tap some also, at least on GM alternators I've seen.

By measuring current in series as I described, this time between battery positive and starter solenoid, you can see how bad the total is. You can also reconnect the battery, then disconnect one wire at a time from the starter solenoid, connect your meter in there and see if you can isolate which one it is.

Mightly be a flaky solenoid. Is the starter warm hours after sitting?

It's even possible that a bad ground somewhere is in effect connecting two normally separate circuits in series with strange results.

Good luck, let us know how it works out!
-Smoky

 

question, i have the fender mounted starter solenoid....what's the little silver box under it?

 

A little flat box that might say MOTORCRAFT on the top? Probably your alternator regulator.