Heater Fan not Working 2001 XJ

The fan for the heater does not work on my 2001 XJ, It makes a buzzing sound, which i traced to the relay located behind the glovebox.

I have access to several parts jeeps, so i have been throwing parts at it to see what is wrong, so far i have tried...

- replaced blower motor with known to be good unit
- replaced relay with known to be good unit
- replaced control switched with known to be good unit
- also checked all fuses
- checked the resistor, the relay buzzes on all speeds, and when the resistor is unplugged it only buzzes on high, which is expected, so i dont think the problem is with the resistor, but may be wrong

Nothing seemed to help, still makes the buzzing sound at the relay, and the blower motor does not turn on...any ideas ???

also on a side note, does anyone know what causes a relay to make a buzz noise like that??

When a relay buzzes or chatters usually it is either caused by corroded/pitted contacts or a weak engagement coil or both....
My vote is for a bad relay....