heater blower motor on 1990 Mercedes-Benz 300SL

I installed a heater blower motor in my 300sl. And the motor only blows on the lower speed. When i first installed it the motor blew on all speeds. After five minutes in only blows on the first speed..

1 answer 1 comment
There is a blower motor speed module that controls the speed of the blower motor , I would inspect that. The wires from the blower motor get power and ground from that component.
where is the blower motor on the 3oosl located?