2000 F250, 4x4, CCSB, automatic, V10. Electrical gremlins are driving me insane. Mainly after it rains a considerable amount. If I don't disco the battery it has to be jumped, overnight to go to work, end of the day to go home. New battery and alt. I assume the disco isn't great for the computer with doing it twice daily? Considering a remote disco so I don't have to pop the hood every time. I'm guessing a backup battery for the computer would be a good thing. What's the proper way to wire said backup battery?

 

If the main battery or batteries are being drained, then the aux battery you add is going to be drained also. Easiest would be to plug the truck onto a charger when it sits. You will have to park it near a 120v receptacle, but you can mount a small battery maintainer that you can buy at Walmart in the engine compartment somewhere and hook it to the battery, and have the cord coming out of the grille like a diesel. Just plug it in when you park it.

If you go to work and leave it sit 8-10 hours and it won't start then, then you have a serious problem that needs addressed. Have you ever put it on a charger? I am wondering if the battery is fully charged when you leave the house, how long will it last before it needs charged again?

 

This only happens after a good soaking rain, as long as it is dry I have no issues. Usually takes days of dry after a soaking rain to go away. The truck sits for about 14 hours once I get home from work until I leave the next morning. At work it sits 9 hours. And yes, it sees the charger regularly. When the issue rears its ugly head the battery will be dead whether in the morning (14 hours) or when leaving work (9 hours). Just last week when my wife got home she came in and told me my radio was blaring....of course it was raining. It apparently turned itself on at some point, it's a factory radio, not aftermarket. And don't make the mistake of leaving the fan in any run position and hvac in any position but off because it will either keep running (sometimes) once the key is off/removed or start running at some point later. Just the other day (yes, raining) 5 minutes after getting out of the truck at work the horn started honking, no alarm, factory or otherwise. Open the door and it quit. Close door and go back inside, honking again so I just pulled the fuse and then figured I best disco the battery. I've had both the alt and battery tested and they are good and both less than 1 year old. Battery is a Diehard AGM. I'm mainly interested in a memory saver type setup but most of those I see require a second battery to connect them to. I'd like to incorporate a stand alone auxiliary battery on a switch just to power the ecu once I disco the battery. That wouldn't require (at least I assume not) daily recharging. I assume with the battery being disconnected twice a day the computer is in a state of constant reset. My limited knowledge tells me that is sub optimal. The whole damn situation is sub optimal so until I sort it out I'll install a remote battery disconnect. Its 28 bucks and at least I wont have to pop the hood twice a day, especially when its pouring rain.

 

We haven't had one of these in awhile, but your post brought back my memory when reading your symptoms. Your truck is new enough to have some fancy features to it, but old enough to where these features are not integrated with a bunch of smart fuse boxes and body modules. Your truck has what they called the "GEM" module. It's a box with a circuit board in it that has all the automated features of the truck inside it.

The GEM module works fine until it gets wet. Your generation of truck had a terrible time with the windshield leaking. These leaks would run down the inside of the firewall and guess where the GEM module is mounted? Yep, inside the vertical firewall on the driver's side. Also your main fuse box is near there, so it can get water in it too, and corrosion can set in.

I would pull the carpet back on the driver's side, and see if water has been leaking down over there. You can also check it after a rain and see if it's wet. If it is, hopefully there is not too much damage. To repair it, you simply take the truck to a glass shop and have them re seal the windshield. It would be wise to pull the GEM and also check the fuse box to see if there is some impending event that is going to happen from corrosion and bad connections.

 

Rubber floor and yes it gets wet. I need a new windshield anyway, been cracked since I got the truck 11 years ago. Thanks.