heater /AC fan problem on 1989 300E

Sometimes my heater/AC fan will sometimes come on and blow in the cabin and sometimes not. Is it overly sensitive to inside temp? When I set it to maximum AC or maximum heat, it still will not come on when outside temp. is around 50 degrees.

I've checked the fuses and the A/C compressor is running. Don't know if any of the relays behind the fuses that control the fan.

Shouldn't the fan come on full blast when the setting is at minimum temp. and the fan speed set on high rather than auto. no matter what the outside temp.?

Thanks for any insights.

Try turning key slightly counter clockwise after starting car!!!!

I've had this problem for at least 50K in my car. The fan
runs when I turn the key slightly counterclockwise after
starting car. I suspect the lock cylinder is going south.
Perhaps,next thing to fix.

Gary

[jeffsr]

What happens when you hit the defrost button. It should come on full blast, except if it's really cold and then it will wait until the coolant is at at least 40c or so. Try it. Let us know..

Thanks for the suggestions, guys. After doing a search on similar problems on this site, previous posters suggested checking the SEPARATE fuse outside the main fuse box and on top of the shock tower.

SURE ENOUGH, the 30 amp strip-fuse located just in front of the main box was cracked in half. Replacing it resulted in an immediate resumption of fan motor!

Anyone having a similar problem needs to be aware that the fan motor fuse for the heater is not included in the climate control fuses in the main box but is separate and by itself. (Now why would Mercedes DO that?)

Any other hidden fuse locations I should be aware of? Thanks for your help.