Blower fan stopped working

My 2000 Buick Century heater fan stopped working all of a sudden. The fan motor is used (replaced with one from a salvage yard and is in good shape). I recently replaced the blower fan resistor (the fan only worked on high speed). After changing the resistor, the fan worked on all speeds - for 1 day. The day after, the fan did not work at all - tried another resistor, no luck. When I turn the fan switch towards high, I hear a clicking noise coming from the resistor area (unless there is a relay or some electro-mechanical device that would make a clicking sound when the switch is turned to-and- from the high setting. Any ideas/guidance on how to possibly fix this? Thank you.

Welcome to AF.

First, since you got a salvage yard blower motor, I would try jumping it with straight 12 volts, as it could be bad (very common issue on these cars). Second, the hi speed relay is built into the resistor, so you may have gotten a bad new resistor. Lastly, you may want to check the switch in the heater control head, as it's fairly common for the switch to melt due to the excessive current draw associated with a bad motor and/or resistor.

Thank you - I will check these items

I was about to post the same thing when I saw yours..my 2000 Buick Century is doing exactly the same thing. The blower only works on high speed. I was wondering where that resistor is you're talking about and how do you change the switch. I suppose you have to tear some of the dash out.
Joe