I'm giving this another chance. Bought another bulb today which is 10W. I will install it tomorrow.
I don't know when my bulb burned out but it is out ----- for the 4th time in less than a year. So ---- I'm not replacing it period. I have a flashlight handy for when I need to rummage through the frig.
This is just one of those apparently unsolvable problems with a motorhome.