Just wanted to share my experience on this matter. I own a '99 Bonnie and when I searched the web looking for advice there was a lot of talk about checking the resistor and relays. I did all of this and still had the same problem. So I pulled the dash bezel and checked the switch itself. The back was melted. Whether anybody else posted about checking the switch, I never found out. So, just in case you haven't done it yet, check the dash switch. You'll be very thankful to have an easy and inexpensive repair.

I had that happen on my 97SE years ago.
Note that only trim levels with the manual fan & temp controls will have this switch. Higher trim levels will have the ClimateControl system, so this switch won't exist.

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PontiacDad at WCBF `08: "By any chance, was his name. . .Radomir?"

R.I.P. 10/31/15: 1997 SE: "Silver Shadow"
`05 Mercedes S500