Here is a good one. The RT blinker would flash fast like bulb out, but both filiments OK. Naturally you may think bad ground or wiring. Here is what I found. The newer (cheaper made) bulbs have harder tip/contacts than in the past. So everything looks right untill you look very close at the terminals and see one of them is taller than the other. Replacing bulb fixed it-but had I tested the bulb (which is good), and not swapped bulbs I would still be looking. The older (quality bulbs had much softer contact/ tits to contact the socket terminals.Jeeps vibrate/ride rougher and this is what can happen.SO if you have an issue like this try a new bulb before getting out the test light, or electrical meter and spending hrs checking.