Assuming your aux fans are not coming on, Here is a test .
There are two auxilary electric fans in front of the radiator. With car
off, see if these turn freely by hand.- If OK >>>>>>
There is a 2 wire sensor on top of the thermostat housing . It has a blue
It turns the fans on to high speed at 105/107C.
With the car running, unplug this connector and see if the high speed fans
come on. [ if yes , you have a bad sensor] If NO , the most common fault is the
fan feed fuse.
This fuse is not in the fuse box. It is in the relay box behind the fuse box.
This will require the removal of 6 phillips holding
screws for removal of the lid.
You will now see the relays . The one in Slot "C" is is the high fan relay and
the fuse will be on top of this relay.
Pull the fuse and check it.
While you are there , the next relay back
[ slot "B" ] should also be checked . This is the fuse/relay for the low speed
fan. This fuse was originaly 15 amp, but has been modifies by Benz 25, so do
that while you are in there.
If you found a bad fuse , relplace and repeat the first test at the sensor
for fan operation. If OK,
take it for a ride ..and let us know ..
Don't use a/c on first test . as a/c is low fan operation on 124s.