Auxiliary fan 300E 2.8
 

Please help
One of the auxiliary fans is not starting in the first stage.
Only the fan in the driver side is spining. A soon as the temperature is raising, the driver side fan is icreasing its speed and the other one starts directly in second speed cooling the engine down to 87 C.
What coud be the problem?
How the relays are set up to work with those fans?
Each fan has his own relay or each relay is responsable for each one of the speeds?

Fans are wired in parallel. so they work together, regardless of which speed circuit is being called for.
There are two circuits with their own relays/sensors. But they each use the same fan motors.
Low speed is a/c pressure activated and high speed is engine coolant temp activated.
If one fan does not run , it is the fan motor that is bad ..
[ bearings/brushes are the usual problem]

Thanks for the input
 

may be the brushes because the bearing are moving very good ...no resistence...but why the second speed work perfect?

Worn brushes show up on the low speed due to bad contact , whereas on high speed , the increased voltage will get it started .
Sometimes you can get it going in low speed by flicking the motor by hand ... a sign of a failing motor..