My 96 f150 with 5.0 is my plow truck. It only gets used in the winter and maybe a couple times in the summer. When i tried to start it after a couple weeks of sitting the battery was dead. I put in a new battery yesterday and it started right uo but when i came out today to start it it was near dead and the truck would not start??. Where does one begin to find out where the drain could be... any help guys...

 

It may be easier to disconnect a battery terminal when you park it.

Check for lights that stay on - dome light, brake lights, underhood light, etc.

 

I am doing just that for now but in winter when its 20 below and 3ft of snow on the hood i'd rather just get in and start it then plow. I will check some things out using a meter, maybe pull fuses until i see the drain stop on the meter.

 

Bluegrass has a good thing to check in your other thread.

 

I had the same problem with my 84. Battery kept dying but it would start and run with a jump. It did that 3 or 4 times then the starter completely fried. You might have a short to ground in your starter. If not, I suggest you get wiring diagrams for your truck and start taking continuity measurements with an Ohm meter.

 

This is a common problem on a Ford. Most likely the alternator is bad, especially the final diode. The alternator will charge the battery but if the final diode is bad, when the engine is turned off, the diode allows the current to flow back out of the battery thru the alternator back to ground. The easiest way to check it is to disconnect the alternator main wire and watch for small arcing. If it arcs, the diode is toast. The diode acts like a gate that allows current to run in only one direction- from the alternator to the battery but closes off the current from going back into the alternator when the engine is not turning. There is always current at the main wire of the alternator, it does not turn off with the key. I'm not aware of any rebuilder or auto parts that has the ability to check the diode. They only check for output. If you need to replace it, make sure to buy new or expect to have the same problem.

 

I took the alt out and allowed the truck to sit for 2 days and it started right up!!. So i have to assume the alt is bad. I will replace it this week. Thanks for the help.

 

I had the alt checked at a shop and it failed for all tests, replacement was 99 bucks, it's in and it starts no problems yet.......