For about a year and a half now, if I run the headlights, and the fan on high, or Headlights and A/C the lights flare (get bright and go back to normal sort of fast depending on the revolutions of the engine).
About 3 weeks ago the volt light came on. I took the car to Autozone for a free diagnostic. They said the battery was going, so I bought a new battery (from Napa Auto.. I don't trust Autozone batteries)
Ok the Volt light came on a few more times but then went out and stayed out. I thought the problem was fixed.
This morning I go to start it up so I can go to work. battery is DEAD! Luckily I still had the old battery (thinking that it was still the old battery causing the issues, but never got around to taking it in to get the core charge back). I connected the old battery and the HVAC fan inside the car came on. I disconnected the battery and connected the neg cable again.. The fan came back on again. I started the car up (which started just fine) and shut off the blower. It stayed on! I pushed the ECON button and I have no light for the fan speed.
I turned the car off and pulled the key out and the fan is still running.
SO.. do I need a new ignition harness since i DID see it smoke a little right after I got the car 4 years ago, do I need another HVAC computer? I'm getting a new battery tonight, for sure. I know I probably need to change out both POS and NEG cables though.
Any suggestions?
(90 Electra Park Ave)

If this is an auto temp system, chances are it'* the blower control module gone bad.....problem is, the blower motor can possibly spike and take out that brand new module.....might not be a bad idea to replace both...

Any guesses on the price range of this module? How hard is it to get to?

I ordered the part through Napa. They had the totally wrong blower, and the control module was going to take 7-10 business days to come in. Total price was going to be $78 before taxes.
Went to O'Reilleys and they couldn't come up with a fan or the right control module.
Special ordered the fan and module from Autozone. Went out there this evening and they had the wrong mounting for just the fan, but I made it work with some washers. The module was wrong. After I told the guy over the phone it was a 6 pin not a 3 and 1 pin he STILL ordered the 3 and 1 pin. So this guy looked up the price. $197.00. I declined.
SO.. I went eBay shopping. Bout the module for $30 and free shipping. Talked to the guy since the module looked pretty clean. He said his dad just replaced it a few years ago, then this past winter rolled the Buick in an ice storm, so he was parting the car out.
When I went to Autozone, I returned some brake pads I purchased back in May, unopened.The typical brake job ended up costing the entire replacement because the brake caliper bolts were stripped (the inset star heads were all messed up). Since it'* usually 90 at 5 am here in the morning, I wasn't going to mess with it. Took it to a VW friend and he ended up replacing the bolts, plus also turning the rotors for me.
Ok So New Fan $38.00 - credit for the brake pads ($35.00) came to $4.22 because of tax. The module came to $30 and free shipping, and also will be here on Thursday. A whopping $39.42! LOL
Supposedly this module goes out a lot and the same thing happens, the fan blows on high and runs the battery down. They used this module in many other cars too until switching to a different model.
So, thats the fix on this one. Oh yea.. the old fan was sort of hard to turn, and was full of dust and dirt. I guess that'* what 24 years worth of use will do.

Glad to hear you are getting somewhere with it, let us know how it goes once you get the module in.

If the old fan was hard to turn, good thing you replaced it.......basically the fan motor spikes and takes out the module...

Yes. Although I drove it to go get a laptop from a friend tonight (luckily we had a rain storm go through so it cooled things down to 92 instead of 115, but we had 90% humidity. LOL) I noticed that the flaring of the lights is much more faster, but they don't dim as much. Maybe the fan and module were helping the situation, wherever it is.
Just got confirmation, the module part should be here Thursday.