Wife tells me that a light is out on the Jag. I check and the driver’s side bulb is out. I open the hood and see that the bulb glows but does not fully illuminate. Get new bulbs and replace the driver’s side bulb. Have wife put car in reverse and drivers side works but now right bulb is out. Take it out and it glows but won’t fully illuminate. Replace that bulb and both work momentarily. Now one is out again. What’s going on?

 

Bill, take a close look at the black ground wire connected to the circuit board that holds the bulbs. The factory put a too small wire in, many of us myself included, have run aproper sized ground wire from the ground plane to the nearby nut on the rear of the car.
while this is a common issue, I'd think it'd create a few more issues but it's a fast check (melted wire, obviously compromised connection).

Frankly since this is just a 12v ground, you could safely pull off the rear light plate like you were going to changethebulb, take a bare wire and touch 1 end to bare metal on the car by the lights (unbolt 1 of the nuts a few turns for connection point on car?) the other end to the silver plate around the lights (the big metal trace is a ground plane). Make a good connection by scraping around a little. Does light brighten? Yes = that's the issue. No? Wiggle the wires, move the bulb around. Any change?
How clean are the bulbs contacts? The socket?

Let us know. John

 

Thanks for the quick reply. I'll check out the wiring today. Currently, they are both illuminating correctly after I changed out the other bulb....so now have 2 new bulbs in.