1994 945T 149k miles.

I recently posted concerning battery maintenance, namely how much water to add to the vent hole... The day I posted that question, Monday I think, I had added enough distilled water to almost fill the vent holes, at the same time I cleaned my battery posts and the mating surface of the clamps. Oh, the car also had a burned out driver's side headlight, swapped in another that I had laying around and all is well.

Yesterday (Wed), coincidently, my wife calls me after going to the gym and says the car won't start. Mind you it's snowing pretty heavily, I'm still at work dealing with my own problems, she's ~15 minutes away (on dry roads), and I don't have snow tires on my 765. Made it there without issue to find that indeed the battery was dead. Idiot lights worked, dome light, etc. But when trying to crank the car over there's not enough juice to get the starter moving. Connected the jumper cables, let the dead battery charge for about 5 min and the car thankfully cranked and started. At least I could get the car home to check it over.

Took the battery to the local Interstate dealer/garage. They threw it on the charger for awhile and did a load test, all is well with the battery. :( That means I have to actually diagnose the problem, how cold is it outside? Got it home, installed it and checked the battery clamps, hmmm, not really oxidized but I didn't see bare metal so I took some sand paper to them. All connected and clamped down, the car fired right up! Sweet, it must have been oxidized connectors. Took the car with me back to work, just down the road, and it sat there for ~6 hours.

You guessed it. The car wouldn't start, same symptoms although something very odd was happening with the key in KPII.

1) Heard a humming/buzzing noise.
2) Tachometer would move from 0 to 4000rpm and hold there for awhile and release to zero again, each turn of the key made the tach jump slightly higher every time.
3) Idiot lights all on, dimmed as I tried to crank it over. (expected)
4) Found the source of the buzzing noise coming from the driver's side seat heater switch which was "ON".
5) Turned the switch off, buzzing and wacky tach stopped.

Now my question(s). Can anyone tell me if there is ANY connection between the seat heater switch and the battery? I'm thinking perhaps a relay that is stuck in the closed position which would a) buzz and b) drain my battery. (i.e. 240 series cars having one of the relays in the electric lock system fail and drain battery, BTDT). Also, what is up with the tachometer jumping and seat heater buzzing?

The battery is presently being re-charged. Seat heater switch is off. I plan on pulling the charger tomorrow before work, confirming the car starts, and letting the car sit all day. With any luck, the battery won't drain and I'll have found my problem.

Thanks for your thoughts!!
Bean in RI
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'80 242GT 93k, '94 945T 139k, '89 765T 68k (new '94 B230FT)