sounds like it could be regulator but clarifying further...
try swapping the switches left to right just to make sure it's not a switch issue. You don't have to actually flip the plugs, just remove the harness from one plug and put it on the other. FWIW, you can very easily DIY the regulator too. If that is truly the issue, first time DIY ~ 1.5hours and pretty basic/not too technical. Use the search function for detailed threads regarding.
Good luck
