Other than a defective motor, a bad switch or blower motor resistor assembly can cause an inoperative heater blower motor.
Resources for the Repair and Maintenance of your 1990 Mercedes-Benz 420SEL
1990 Mercedes-Benz 420SEL
1990 Mercedes-Benz 420SEL Problems
It is not uncommon for the idle air compensator to get stuck in one position, resulting in the engine idle speed (rpm) being too high or too low. Replacement of the failed compensator may be necessary to correct this concern.
The timing chain and timing chain guides wear; they should be replaced every 100,000 miles.
The rubber boot connecting the throttle body to the intake
manifold tends to crack. This can cause hard starting, rough or erratic
idle, and engine performance problems.
Valve stem seals may wear and cause the engine to burn oil. this can contaminate the catalytic converter and cause it to fail.
1990 Mercedes-Benz 420SEL Questions and Answers
1989 420 sel new valve job having problems hard to start when cold and after driving up to normal temp also the eco neelde stays in center when at a red light and the car is in gear
what is coreect atf fluid for 420 sel and where does it get filled once drained
car stalled while on the road. plenty of fuel(half tank) turns over fine. no prior problems. Any suggestions or ideas
I have a 1986 420 SEL and had to replace the window. The plastic clip which is used to attach the window rotor to the actual glass was broken and I went to the dealership and got a new one. How d...