72 Parking & Turn Signals

[CJM72]

Hello All! I'm having issues with my front bumper mounted parking / turn signal lights in my 72 Blazer. Searched all over and most people just point back to the wiring diagram.

Symptoms:

Drivers Side bumper light and marking light turn on and off at the same time when the headlights are off. Passenger side bumper and marking light alternate. When the parking lights are turned on the both marker lights turn on and only the drivers side bumper light comes on. With the parking lights on, the drivers side bumper light no longer flashes when the blinker is turned on (stays lit)...passenger still flashes but no parking light.

My understanding is that the bumper lights should be on when the parking lights are turned on. I also believe that the bumper and marker light should alternate when the blinker is on. The front harness in this Blazer has been replaced and looks brand new.

Could I have the wrong bulbs in the bumper lights? Any pointers on troubleshooting this?

Thanks! Chris