First of all, do you have the lighting dimmed for the instruments at all?? This is the first reason I would think would cause a lower than normal voltage.
This thread finally made me sort my bulb out this afternoon when I got home. I would turn my lights on and nothing would light on the window switch pack, I had to give it several hard taps with my hand before it would light.
First of all, I had the switch pack totally out and removed the bulb. It looked fine so I lifted the little metal prongs on the bulb to try and make better contact with the holder. Still it didn't work so I rechecked the bulb and took the green rubber cover off to see the bulb more clearly and still it looked fine.
The bulb looked the same as one of the bulbs the instrument pack uses so knowing I had a few of those spare and lying around in the house I went in and grabbed one along with my voltage tester. I put one of the spare bulbs I had in and it now works perfectly, put it all back toghether and everything is now fine. I didn't end up testing the voltage though, sorry
As said, the bulb is 12v 2watts. The bulb I put in was meant for the instrument pack so is only 1.2watts. So, at some point I guess I will replace it with the proper wattage one but I cant seem to find the part number for the correct bulb.
So, even if the bulb looks fine it might not be.
-Wills