1980 F250 300 I6
Drains the battery if it sits for a while. I have done all the tests, light tests and multimeter tests, nothing has changed. The only thing is this truck does not have a working ignition key. The previous owner lost the keys so he just busted the column off and pushed down the rod to start the truck.
So my question is will not having a working ignition cause the battery to drain, and if so how can I disconnect it so it won't cause the battery to drain?
This is not a daily driver, so I don't care if it has a key or not, its a farm truck that is not ever going to be off the farm.
When I did test it with a multimeter, disconnect the ground and connect the multimeter from the ground terminal to the Neg. battery terminal it reads what ever level the battery is at, so if it reads 12.5 volts on the battery terminals, it will read 12.5 with the Neg cable off and the multimeter connected to the lose terminal, this should be 0 correct?
Truck runs, starts and charges fine I haven't had the Alt. tested but the battery is brand new, so since the truck doesn't run anywhere I just put a Neg. terminal off switch on the battery BUT I would like to know what the hell is causing this problem.
This has been a great site with all kinds of information.

 

If you just push down to start it are you leaving it in Run, or is it getting turned to Off? Or, pulled past Off to Acc? If the latter then there are things, like the radio and clock, that get powered in Acc.

On your testing, I'm not sure I understood correctly your question. But, a digital voltmeter (DVM) is so sensitive it may well show battery voltage when measuring from the negative post of the battery to the negative terminal of the cable. It doesn't take much current at all to let the DVM show a voltage. The radio, if you have one, pulls current even with the key off. The clock, if you have one, does as well. In fact, even the diodes in the alternator and regulator pull a little bit. So, a test light is better to check with than a DVM.

 

I thought I was not pulling the rod back far enough also, but I pull it all the way back and use the "key release" I guess which is for taking the keys out of the ignition, this pulls the rod back even farther. So I am sure I am pulling it back far enough to not complete the circuit. Unless its going back to the ACC position which I assume would supply power to the radio and such. It does have a radio and a digital clock which both are still powered, I am going to pull those fuses out. But before I realized there was even a "key release" I was not using it so it made no difference.
Does the radio and clock pull power no matter what position the key is in? Even if they do there is no way they will drain the battery overnight.
Is there a way I can tell what position the rod is in by looking or testing somewhere for voltage or amp draw?

I did the exact same test with another 300 I6 industrial engine we have on a drill truck to see if it pulled anything and it pulls nothing, of course this engine has nothing hooked to it but the starter and alternator so that might not be realistic.

I guess I will drive it down to autozone and have them test the Alt, I am thinking its causing the problems but who knows this truck is pretty rough in the body it might have a wire rubbed out somewhere causing problems.

Thanks for the reply.

 

These should not be powered in a vehicle with the key in the "off" position, which tells me that something is still not where it should be, perhaps you are indeed putting it in the accessory position by pulling the rod all the way back? I know that my battery will drain if I leave the key in the run position over a few days. In "off" it seems to hold fine though. I don't know for sure, but your radio and clock might not be the only things powered with the key in the accessory position, and simply pulling those fuses might not solve the problem.

 

On one truck I had the lock would release the key in either Off or Acc, and there wasn't enough difference in feel to tell the difference by hand. And it would pull the battery down some if left in Acc. But, then I realized that in Acc the clock was showing the time but doesn't in Off, so that became my test.

Yes, the clock and the radio both pull some current even in Off as they both have always-on connections. Otherwise the clock would forget the time and the radio would forget your presets. But, it isn't much current draw and probably isn't more than the self-discharge rate of your battery. (All batteries slowly lose their charge, regardless of being connected to anything or not.)

It is very possible that you have a blown diode in the alternator, and that will cause it to drain the battery over time. But, the parts store can't fully test the alternator in the vehicle. They can check to see if it is charging, but won't be able to check the diodes as they won't know for sure it isn't something else in the vehicle pulling current. So you have to take the alternator out to have it properly checked.

 

I was wondering if they could test it in the truck or if it had to be taken out so thanks for answering that question for me. The radio is the old school push button presets, haven't seen one in years!

Guess I will just have to play with the rod and see where it needs to be to make the battery happy. Hell when I went to buy the truck the guy selling it had no idea how to start it, his buddy owned it and he was on hos 2 week a year reserve training in the Army, neither one of us had any idea how to start it. We finally got the friend on the phone and he told us the trick.

I really appreciate the help and answers, like I said its not a big deal, but it bothers me that its not right.

 

One thing I forgot to mention, when I did the test light method it glows as bright as if I have the test light hooked directly to the battery. So the draw is pretty big. I would think that if it was something minor, like a radio or clock the light would be pretty dim, but it shines very brightly, like I said there is no difference between it hooked to the battery directly or just hooked to the neg. terminal and the loose terminal cable.

 

Houston, you do have a problem. If it glows that brightly then something is drawing more current than either the radio or clock. (I forgot that you might have a pushbutton radio.) I would start pulling fuses one at a time until I either found the culprit or I realized that it isn't powered via a fuse, which means it is either the alternator or the regulator.

Make sure it is going into Off and check again. If it still lights the light brightly then I'd pull the alternator.

And, by the way, you must have a tilt steering wheel as that's the one that has a part break and make starting it difficult. You can buy the replacement part and here's info on how to fix it.

 

What i would do is hook the testlight back up to the loose negative terminal and the battery, and then play with the rod while watching the light. If there is a sweet spot where the light goes out or is very very dim, then that's off.

I am not sure the store tester will pick up a bad diode. Theoretically it would, but the alternator will still function for the most part, just being down a little bit on output power and the waveform won't look as good coming out of it. Maybe their tester can pick this up, or you can just pull the wires off the alternator and see if the testlight goes out.

 

Good point on the diode. Well, all of it really. But better check the diode at home as Dave said.