Definitive :-) answer needed -- does aux fan come on whith AC [190E 1985]sssss

Aux fan does come on when A/C is on... However, there is another trigger for aux fan... which is secondary circuit that in the event of overheating at

Majority of the time when aux fan doesn't work when a/c is on...wordy I know... is the thermoswitch... or the fuse if it doesn't come on at all... Last resort is dead fan.

Yes, it comes on with the A/C on. It is triggered by the pressure of the high side of the A/C. On top of the receiver-drier is the pressure switch. If it is green, it turns the fan on at 325 psi. If it is red, it turns the fan on at 275 psi. Back in the early 90's, there was a big ACC update for 190E's [in the USA]. Part of it was putting on side shields so all the air would go thru the condenser, instead of around it; changing both drier switches; and adding wiring and a black top relay so the magnetic clutch fan on the water pump would lock whenever the aux fan was engaged with the A/C. This lowered head pressure and vastly improved the cooling capacity and kept the manifold hoses from blowing up.

I suggest you start by looking at your fuse... take it out and put in a new one.

My C-class blower fan (main fan or Aux) often doesn't come on, suspect it's not the switch because the functions of the switch do work when the fan actually runs. Could mine be the same problem? if so, where is the thermoswitch and how do I test it?

Thanks