At what point does the supplemental fan go on on a 124? It was 95 out and the fan was not going on eventhough the compressor was trying to push freon around. I don't think it goes on when AC is activated, but at 95 ambient, I would think it should be helping with the cooling.
Is there a test of relays or temp. sensor when this should activate.

Thanks.

Let me share this info I picked up I don't remember where.

"There are 2 temperature activated switches that operate the Auxiliary Fan.....

1) Temperature Switch 100*C in Thermostat Housing for Auxiliary Fan

2) Temperature Switch 62*C in Receiver Drier for Auxiliary Fan"

I have the same Aux Fan issue on my '84 300DTurbo'. I know my fan works, so then either or both Temp Switches must be the problem.

Then let's hope for experts to chime in and shed light upon us.

I think most Mercs of the era are set up the same as my '88 190E 2.6.

The engine driven viscous fan clutch tightens at about 100C coolant temperature, which causes noticeable "fan roar" at 2000 and up.

The auxillary electric fan(s) engage high speed at 105C coolant temperature, and they can also usually be heard from the drivers seat, especially if the car is not moving.

The electric fan(s) are also engaged, at low speed, by an AC system pressure switch, but this low speed engagement usually can't be heard from the drivers' seat, and it usually only occurs in stop and go driving when there is insufficient dynamic air flow to provide sufficient condensing capacity.

Duke