Key off battery drain/discharge

Sounds like the ignition is stuck on, with the click.

Thanks, I'll check into that.

I disconnected both wiring harnesses going to the alternator, and pulled all the fuses again, and got ~370 milliamperes.

Like I mentioned before, when first putting the multimeter in the circuit, there is a surge of over 40amps, then it drops back to ~370 milliamperes. I read in a web forum that "Ford specifies 500mA (0.5A) maximum parasitic drain"...

I checked the voltage across the battery terminals while the engine was running it was over 14V. I'm starting to wonder if it is intermittent.

I have had two Fords that had bad diodes in the alternators. When they go they let the battery drain down, seemed like it was overnight or maybe a couple days. I never figured a fix except to buy a new alternator.

I have read about other owners with the bad diodes problem.

But I have disconnected both wiring harnesses from the alternator and I still get the same amount of current draw, around 370 milliamperes. I get over 14 volts across the battery while the engine is running.

Maybe the diode problem is intermittent. I may just take the plunge, change it out and see what happens.

Thanks Eddie

I had an old T-Bird do this and it about drove me crazy trying to track it down. Turned out of be a short in the solenoid switch. Replaced it and the problem went away.

This wouldn't surprise me in my F150. I remember over the summer a couple times I noticed an electrical noise, relay, small motor, of some sort that ran momentarily while the key was out of the ignition. I haven't made any more attempts to troubleshoot recently. Just am leaving the negative battery cable disconnected for now.

There is a thread in alt.ford.trucks (and maybe some others) that I just found that I'm going to follow. The original poster has same year F250 with a battery drain.

Thanks

Yep. the rectifier is bad. That was chronic with that design. and yes, if it got hot enough to melt the sheathing because it was touching the back of the alternator, then the unit not only has burt diodes in the rectifier, but also the stator winding could be close to toast.

the origional rectifiers wern't the greatest but under stock conditions would usually last past the warrenty (great, huh...) and I've seent hem go up to oaver 100,000 mi. the aftermarket parts were crap. no one made rectifiers better than the origional and even then the OE wasn't good enough. Transpo electronics was first to bat to build a better "mouse trap". there rectifiers are radically better. so were Renards. But now the Renard line is tanked because they and transpo were both bought out by WAI corp. And they chose Transpo's like to be a bit superior.

if you decide to get an exchange unit. as the parts house sales geek, what brand of rectifier is in the unit. Of course,they don't know, but they ought to be able to call HQ and the reman place and find out.

the rectifier number should be something like a transpo F-192 fxhd. or something like that. anything less is almost a waste.

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Here's sopmething else. does your truck have electric door locks? a friend of mine had the same pickup youare describing,a nd when he got it it had a fresh alternator on it. he brought it to me and it tested fine. still had battery problems. I came down to his shop and looked at it and it was odd. I would disconnect the ground cable and tochi it back to the bat. terminal and we'd hear an ever so slicht noise. Not a click but someting faint and odd. after listening around, he noticed that the manual door lock plunger was wiggling on the drivers side door. What was going on was that his electric door lock had a defective relay and was trynig to lock the door but couldn't get it done,and was shorting itself out thus draining the battery overnight. he disconnected the electric locks and had no more problems.

i still think the problem is in your alternator, though.