Hi, all, new here - owner of '91 L-6 manual F150.
I've already searched this forum, and found some clues - esp on the 'dead battery' thread of 10/05.
Here's my prob: Random battery discharges (to stone dead) when I haven't left anything on. Replaced a bad alternator last year, then got a new battery. This is third time this has happened after the new stuff. Auto store tests battery after recharge and say it is good. When driving the alternator gauge reads sl above average at ~13 amps I'd estimate. Will start fine most of the time, then suddenly stone dead. OKay in between. I wonder if there's a short somewhere discharging it. I know the wipers are finicky - they stop out of the blue, but will restart when I slam the top of the dash. Makes a comic show in the rain. I also know the aftermarket stereo system is junk/non-working, but looks to be off.
Any tips on locating the short?
If not, is there any way to put a master switch inside the cab to disconnect battery completely when not in use? It's a farm truck, and this would not be too inconvenient, but I really don't want to raise the hood everytime.
thanks,
sean

 

I'm betting on a short from the aftermarket radio...

 

Yeah I agree on the radio, I'd rip it out and be sure everything looks good and all exposed wires are covered and then wait. Do the same with the wipers if it isn't the radio.

 

Make sure EVERYTHING is off first. Take off the negative battery cable. Using a test light attach one end to the post and the other to the connector. If there is a short the light will glow. Pull the fuses until the light goes out to narrow the circuit down. Also, you can purchase main battery switches. They were installed on every emergency vehicle I have seen. But the cost of the switch and cables are pretty high just to avoid fixing a short.

 

Thanks, guys, I'll check it out.
BTW, if a short can't be found, and this battery declines from this abuse, if I replace it, is it feasible to put in a deep cycle battery in a regular vehicle like this? Those can tolerate going dead and recharging, etc. Ever heard of trucks with them?
thanks,
s

 

Yes you can use a deep cycle battery as long as you "oversize" it. Just make sure the cranking amps are adequate. Deep cycle batteries are not designed for starting applications. The lead plates don't have as much surface area as do the starting type, which are constructed of a "sponge" type lead plate. That extra surface area provides higher cranking amps but less durability compared to the deep cycle. Deep cycle batteries have solid lead plates and generally will last longer but provide less cranking amps per size.

As far as the battery switch, here are some examples if you go that route. I just googgled this site. I have never bought from them or used the products listed. It is just an example for you. Don't forget to factor in the price of the cables which will most likely be higher than the price of the switch.