I need help my reverse lights aren't working. Any ideas what it could be? It's 1990 c3500 7.4 dually automatic. All the other lights work but the reverse lights.

 

Check your neutral safety switch

 

It sounds silly, but don't forget to check the bulbs - easy stuff 1st - I have had to episodes where both lights were burned out at the same time. With bulb out you can also meter the socket for power. Please report back!