I have an 02 TJ 4.0 sport the other day after starting the jeep i noticed my right blinker was lite up on cluster. I got out of the vehicle and found that both side marker running lights were inop. when turning the blinker on the blinker would illuminate but at half the brightness as normal. i took the bulb out and checked it it seemed fine. when i put the same bulb back and tried to turn the blinker on it just illuminated both running lights that previously were not on but the blinker would not blink it was a solid light and when i turn the blinker off now the marker lights on the right side turn back off . if i use my 4ways all 4 WAY lights work. i checked for corroision near the lights and found none any ideas
Here are a few steps you can take to diagnose and hopefully fix the problem:
A poor ground connection can cause the lights to dim or act erratically. Make sure the grounding points for your lights are all clean and tight. You can also use a multimeter to check for continuity between the light socket and a good ground point on the vehicle (not a bad idea to start with).
I know you mentioned it, but I'd also check the light sockets for corrosion or damage very thoroughly. Sometimes oxidation can prevent good contact, leading to dim lights or changes in behavior when the blinker is activated.
While you mentioned the bulb looked fine, it might be worth trying a brand new bulb or a bulb known to be working. Sometimes bulbs can have issues that aren't easily visible. I've encountered this issue more than once.
Check the relevant relays and fuses for the turn signals and running lights. A malfunctioning relay could cause the blinker to behave erratically. Also, ensure the fuses are in good shape.
Look for any damaged or frayed wires in the harness leading to the lights. It’s possible that there’s a short somewhere that’s causing the issue.
The turn signal switch itself may be faulty or have internal corrosion. If all else fails, you might consider replacing the turn signal switch.
If you can isolate the problem to one of these areas, it should lead you closer to a solution. Keep us updated on your progress! Good luck!