There are quite a few web sites that will show you how the wh works, the manufacturer probably has one with trouble shooting suggestions/instructions.
With the schematic and a DMM, you can chect for power, I would have not only a DMM but a test light. Often it is nice to have a hand free and most meter leads do not have aligator clips, so you need two hands. A test light from an auto parts will do nicelyy.
You do not need to know electronics to trace the presence of power in the circuit. It is generally pretty easy to follow the path if you have a schematic.
A DMM is needed to check for the voltage level.
Also as noted, the year, make and model are needed to give more than guesses.