Okay guys,give me some good guesses. All of a sudden, my 64 F-100 has decided it should run the battery down over night. I have had this truck for about four years now and this is a new one. I've been thru the wires, taken fuses out and it still runs the battery down unless I take a battery cable off. If I charge the battery it starts like a champ. Naturally it would start this in November.
Is there a magic tool I can hook to the battery and it will tell me "the red wire going to your heater switch has a bare spot on it"?
Don't even know where to start at this point. I don't feel any hot wires when it's not running (thought that would be a trick, but it tricked me instead).
What else do you need to know?
The battery is new and it will hold a charge as long as I don't hook it to the truck with both cables.
Gary-R

 

is this a generator or has it had a alt put in ? I would suspect a Bad diode in the alt. You can get a Amp meter and put it in series with the + Battery wire and see how big your drain is. Get one with a smaller scale like 0-5Amps ( electronics store ) or the other way would be to disconect the battery , disconect the Alt ( all wires, and be sure to mark tham ) and see if it still goes down, with the meter you can elimanate things one at a time and see where the drain is Without wateing overnight to see what the results are. Always disconect the battery befor disonecting other stuff. I would check the alt, then the main B+ line running from the starter relay,if that is it then start pulling fuses untill you find the area where the current is being drawn from. also check the voltage reg .

 

I agree with jav409,
Without knowing what sort of charging system you have, there's no real way to figure out what's up with it. . . .

Is it Alternator or Generator and is it OEM or something else, a 64 should be a Generator system BUT. . . . .?

FBp

 

I knew I'd forget something. The engine is a transplanted 302 with an alternator. I took that off and had it checked and everything showed good. I will get an ampmeter and do that check. Most of the truck is stock, i.e. no power brakes, steering or ac. The wife doesn't much care to ride in it in the summer, but the heater will run you out in the winter. All in all it's probably a decent vehicle, it's just that it's November in Indiana and a possibility of snow this Thursday.
I'm old enough to not appreciate working outdoors on toys in the snow.
Now that I think about it I did charge the battery part way the other night, got it running, took the charger off of it while it was running and it died. Maybe I better take that alternator some where else. It probably shouldn't have died like that should it.
Thanks at least for another 'starting' place. (Not necessarily a pun.)
Gary-R

 

Have you recently installed any auxillary equipment like stereo or radio equipment? Some equipment can have residual current drain if the circuits are not completely disconnected.

Once my brake light switch was deffective and was partially "on" all the time. The brake lights glowed so dimly that I never noticed, but they drew enough current to flatten the battery over night.

Do you get any spark at all when you connect the battery cable? Agreeing with previous suggestions, a low range ammeter in series with the hot battery cable and isolating the problem systematically would be a logical approach.

An old battery that really can't hold much a charge often can miss lead a trouble shooting venture. I get leary of a battery approaching 3 years old, regardless of the warranty papers.

John

 

I'm still going to go with the diodes in the alternator diagnosis. I worked in parts for a number of years, and a lot of times the "bad diodes" light on the tester didn't necessarily light up for an alternator that was still bad. They're pretty cheap--I'd put a new on on (as well as a new regulator, if it's external) and see where that gets ya.

 

Bad battery, alternator, or other drain - it can be revealed with a good voltmeter. The check for a current drain will tell you right away if you should be looking at the battery or not. If you have a significant drain then you can trace it down by unplugging one source at a time. The connectors through the firewall are a good place to isolate the cab from the engine compartment but you have to be aware of the circuits that loop in and back out again. My truck has about .13V when measured from battery post to the disconnected cable but measuring current reveals 0.0 amps. Must be eddie currents at work but I have no battery decay. Does your truck have an aftermarket ammeter? Mine was defective and had a drain through its internal shunt.

 

when i have this problem with any thing ill step back and think hmm what dont need the key on to work ie. head,tail light horn charging system then ill just start goin threw them looking for problems maybe if your alt.checked good how about the regulater it could be on when the alt isnt turning

 

I bought an ammeter today and you guys have given me tons of things to do. Thank you all. When I first bought this truck I had this same problem. I undid wires and pulled fuses and had stuff checked (about 4 years ago) and I never did find anything. All of a sudden it just stopped running the battery down. Now it's started it again.
I have printed all your replies so I can take to the truck with me and start checking one thing at a time. John D. I don't have a radio in it at all right now. That would be killer to have the old AM fixed and working.
Raleighdad66, when this happened before I could measure a good 12 + volts from battery post to disconnected cable. I haven't done that check again. Isn't that from the ground or is it the positive? Can't remember for sure. I'm told, "your mind is the first thing to go."
Nealjpage, I remember some questionable sightings when I first had the alt. checked but we figured it was all right. I think I can find the right guy to match this alt for a new one. Anymore, if you don't have a year,make,model, and your date of birth, most of the parts guys can't find a replacement. This thing came with the truck (and halogen headlights), so the only thing I'm pretty sure is that it's gm and not too sure of that. There is a serpentine belt on it.
Thanks again guys, if I figure something out I'll let you know so you can put it in the memory banks.
Gary-R