I have a 97 F350 standard cab, 5.8 automatic. It doesn't get used much, I might drive it once or twice a month, sometimes less than that. A few weeks back was one of those times, and for the first time since I've owned it (probably four or five years now,) it had a DEAD battery. I've replace a battery or two in it, yes, but it always gave me a warning when that was needed.

This time was different. I jumped it, got it started, moved it for my intended purposes that day, charged the battery and left it. A week or so later and it's dead again. Same as before except this time I go looking for the reason. It has a definite battery draw, enough to actually show sparks when the last cable is touched to the battery post. It's not the alternator, nor any of the fused circuits or the relays in the fuse box under the hood.

I was playing with it again today and discovered it must have something to do with the heater/ac unit. I was cleaning the cables and such today with the passenger door open and noticed a noise of some sort when the cable is connected/disconnected coming from the area of the AC unit, kind of a buzz, hum sort of noise for just a few seconds or so, and what sounds like maybe some doors or flaps in there opening or closing. All this without a key in the ignition, and nothing else turned on. I'm wondering would there be a climate control module in a '97 truck that would have battery live circuits? Could that be where the problem is coming from?

It seems to be charging fine when it's running, so I'm debating whether to pursue the issue or simply work on a battery disconnect.