Dometic rooftop air conditioner with a e4 error code

First thing clean the condenser fins/coil. Then check to be sure that the Sensor which is mounted on the front of the condenser that has two wires going to the control box with a 2 pin connector aren't loose. If loose it will set off an "E4" error code.

Possible fault in the compressor not taking up. Please check the main capacitor to the motor for failure.
Remove plug and reset .