When I turn the key to the II position, I get a very faint "buzzing" or "humming" sound which eminates from directly behind the driver's gauges, or perhaps under. I pulled the fuse panel open and could hear it a bit clearer. A very electrical sounding hum. Continues even past turning the ignition and even continues while the truck is running. The climate control is off, by the way so it isn't a fan. Sometimes it happens...sometimes not.

So...what the heck is that!!??

'02 Disco.

 

Possible ABS noise?
Do you have SLS, could be the pump humming.
You might try puling the blower fuse and see if it goes away.
Mike