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

[SeventyOne]

How do the fender mounted marker lights operate? Same symptoms as the bumper blinkers lights?

[CJM72]

I believe they are working correctly. They blink when the parking lights are off. They light up when the parking lights are turned on. Still blink when the turn signal is engaged.

[SeventyOne]

Stock wiring harness?

This makes me think it's a ground issue on your bumper lights if the fender lights work correctly. They are tied together in the wiring.

I believe the brown wire controls the parking light and the light/dark blue control the blinking.

I have an American auto wire wiring kit in my blazer but it should be the same:

[CJM72]

Hmm. I think you might be on to something. I also think there might be 2 issues here. The drivers side parking light didn't light up until today when I was messing with the bulb and wiring. I could get the parking light to come on solid by moving the bulb around or touching the housing to the bumper, but nothing reliably. If both the bumper light and side marker are flashing at the same time, is the bumper light grounding through the side marker ground? How does the bumper light ground? Through the housing and bumper? I'm not sure how the alternating flashing works.

I'm wondering if my non functional parking lights are related to the wiring in the headlight switch. Could be wired up the pre 68 way and the parking lights are not getting power with via the light switch.

Guess I got some more messing around to do!

[CJM72]

One more clue to offer. On my gauge cluster, when I turn the parking or headlights on, the left turn signal indicator lights up solid green. It will flash when the turn signal is turned on but after it will stay on. The right cluster indicator only flashes green when the turn signal is on.