Facts I know:
- 2002 F350 SD 7.3L PS Lariat LS
- Twin batteries are 880CCA each and installed 3 months ago after factory batteries failed to hold a charge.
- Before new batteries... when the truck sat for 3 to 6 days straight it would not start. Couple hours on the charger and it would start.
- After new batteries it seemed ok, I did leave the truck 3 or 4 days but recently it sat for 7, and would not start.
- Full charge on batteries and it'll go 4 days parked.
- In the past, Truck has sat for up to 3 weeks while we were cruising on our boat and did not have a problem. Issue began about 4 months ago.
- Checked all lights, heated seats, radio etc... everything seems off.
- Batteries can sit 3 or 4 days disconnected and hold a charge. Connect them and the truck will start. If connected, they drain.
- Ford Factory Alarm / remote start system has been removed, same issue remains.
- Brake controller has been removed, same issue remains.
- Entertainment system has been disconnected, same issue remains.
- The truck's electrical system is now "Factory"
- When parked as it would be normally, the current draw is about .4 to .5 amps. Seems high to me but then I don't know.

Questions:
I'm sure I forgot to mention something so just ask.

What should the current draw be when the truck is parked?
What should the voltage on a battery be when disconnected and fully charged?
Does anyone have any suggestions about what to check next?


Thanks in advance. I hope to have this SD back on the road soon, I'm tired of driving my wife's Dodge. :-)

Robert

 

Here is a test to find out where the drain is. I am not sure of the routing of the battery cables, but if you are not sure which battery - to disconnect, just disconnect one of the batteries and do the test with the remaining. From your comments, the testlight should glow. So start pulling fuses to try to make it go out. If none of the fuses make it go out, try disconnecting the alternator. If the alternator makes it go out, then get a new one, since one of the diodes may be bad inside.

 

Report:

I isolated a battery and used an Ammeter. I found the truck was drawing from .5 to 1.1 amps wildly. It was moving all over the place, up and down rapidly. With the door lights on etc... it was drawing 4.5 to 5 amps, with some more lights it draws 6 to 6.5 amps. Get the idea? Something is causing a .5 to 1 amp draw under rapid change.

Testing:

After getting the baseline I began removing fuses while watching the meter, I could see the meter through the windshield. Finally on the second to the last fuse (isn't that always the way?) the current dropped to .02 amps and fluxuated from .01X to .03X which I later determined was the error in the meter. The fuse? The Radio Main fuse. I have left that fuse out and so far, no battery drain.

Next Step:
I am going to remove the radio head and reinstall the fuse. If the current draw is appropriate I'm going to add the radio head back, if it misbehaves again I've found my culpret. If I find it's not the head, I'll begin searching for whatever else is on that circuit.

Just and update, thought everyone might like to know.

Oh, and Franklin2 Thanks for the idea!

 

May seem like a silly question, but do your interior lights and bed lights work? if the bulb is blown, but the filament is fused, it may allow half an amp to leak on you like that, and I think those are on the same circuit as the radio.

 

I'd thought about that... all of them work. And, in my truck atleast, the lights are not on the same fuse as the radio. I've been busy so lately I've been driving around with no radio... not that I could hear it anyway with that diesel out front Truck seems fine, no battery drain. So... it's on that circuit somewhere.

Now for the radio head... back at around 12k (now at 50k) I would return to the truck and the sucker would be playing away. Ford "fixed" it. That didn't happen anymore, but it's never been right. It plays when you turn the truck off... when you open the door... when you close the door... until you LOCK the doors, then it goes off. I figured it's a small quirk to live with... until now. If it turns out to be the radio I should have rode them like a wet horse on the Pony Express and made them buy the truck back over the radio. Hind sight... I guess I should walk backwards everywhere.

 

Well, there's your answer. It sounds like something is fishy with the radio wiring. Problem is, if someone messed with it, you may never figure out what it is. If there is one thing I have figured out, even though they have the training, engineers and service technicians do make mistakes, even though they won't admit it. An aftermarket unit may be in order.