heater fan still runs after engine off - drains battery

I read through these posts and think.. wow I've had most of these problems .. but now I have a new one I can't figure out.
Yes the dreaded coolant disappearing act and fluctuating temp gauge has hit me. I top up the coolant almost every 3 days now and can see the outside of the block is soaked, however my oil levels have not risen on the dipstick nor to I see traces of water. So .. the gasket is going/gone on mine too, I would fix this problem if I can get through another one which may be related to this. I thought GM has a class action law suit slapped on them on this matter. Will they fix this? Does anyone know? But here's my other problem
My heater (or defroster fan) stays on.. all the damn time. Its draining my battery. I have to disconnect the neg term on the battery every time I shut the engine off otherwise I'm stranded from a dead battery. I've tried pulling the fuse, in fact I pulled every fuse, and the fan still goes after the ignition is shut off! How can I fix this?Eengine is 3.1 ltr with 244,000 KMS on it .
I'm so frustrated with this van.. Its going to the salvage yard If I can't fix it
:banghead:

OK..1995, (from your profile)....
www.avigex.ca/xport/hvac_diagram_front.jpg
From this, no juice should be available to heater fan when ignition key is turned to OFF.
..but..which speed is running the fan? THe High speed relay is fed direct from battery..and if contacts are shorted, either within the relay or the socket, the fan could run at high speed...thus emptying the battery in a short time...
remove high speed relay...www.avigex.ca/xport/heaterrelay.jpg
It should be all dead then..even low speeds would not run.
Report what happens.....if it still runs, the socket has melted: running high speed for long periods is not good as high amps (25A) are not for continuous use: relay or socket have been reported to "meltdown" in such abuse....

ALso notice fan speed set at the lowest will still run the fan at very low speed..with key on, though. ONly way to turn it off completely is pushing the OFF button. BUt again, if it was running at this "very low" speed, it would still require the ignition to be ON..and then might mean one switch gang in the ignition switch is shot...

You are the goods man. Went out, pulled the high speed relay and the fan shut off. Plugged it back in, and voila, no fan sound! Could it have just been the contacts being corroded? All seems normal again .. I had no idea. I'm mechanically dangerous, not mechanically inclined. However, wrecker man is on his way.. Oh well..