All summer the noise has been gone. Now there is a bit cold outside and I'm putting on some heat inside the blazer again.

After only a 10 min ride the humming/buzzing noise inside the dashboard are back. It's only there when I have the heat on, and even then it's not there all the time. To me it sound like a relay clicking super fast.

Maybe there is a relay on it's way out, but it only shows when it overheats.

It's more to the passenger side of the dashboard, some place around the glowbox' or ashtray area.

Any sugestions to what this could be making this noise?

 

OK, thought I should update you on this problem, as so many took an interest to solve it hahahaha

I now has this mystery problem fixed! And the embarrassing thing is it took my wifes sugestions to solve it. As this sound is only there in the winter, and I have NO clue to what my wife does on here side of the Blazer I would never have thought about what could cause it! Last time we took the Blazer for a run the sound acted up again, we did some brainstorming to what could cause it, and what was different now as it's winter. And out of the blue my wifes says: I'll bet you it has something to do with the heat in my seat! "No" I say, it can't be that easy! "Ok, I'll turn it off for some time and we will see if it comes back!" And it never did! On the way back we played with it "on and off", and every time it was in the on position over 3, the relay would buzz from time to time! Took the control wheel out today and it was corroded inside. Cleaned it with some hot water and comressed air. And the buzzing are GONE!

HAPPY HAPPY HAPPY