[gto4evr]

Hey guys, I noticed something today that I never have in 40 years of driving this car and the wiring diagrams aren't helping.

with the headlights off, both with turn signals or the hazard lights, the front side marker light is flashing in time with the front turn signals.

with the headlights on, the side markers flash opposite of the front turn signals.

I've been staring at these wiring diagrams for hours because initially I thought I had a grounding problem. on a 69, the side marker only comes on with the lights and never flashes with turn or hazard. from that bulkhead connector to the lights, the wiring is basically the same between 69 and 71. only difference is they're jumping the light feed from the turn sockets to the side markers at the connector in 69, and 71 they moved the jumper down to the sockets themselves. I know a 69 column is interchangeable between 69 and 71 so there can't be a wiring difference in the column switch. the wiring diagrams don't do a good job of showing you what's between the back side of the bulk head connector and the back of the fuse box/column so that's where i get lost on tracing the path here.

The only thing I can think of is that they're sending power to both elements of the 1157 bulbs in the turn signals so that's why the marker light comes on when you engage the turn signal. Okay, I can understand that (if it's really the case), but....when the lights are on, why would the marker light go off when the turn signals engaged? it would be pulling power from the light circuit that's powering the headlights along with the tail lights wouldn't it so why would it flash out of time with the turn signals? when the lights are on, the turn signals act just like the tail lights with the bulb staying on dim when the turn light is unpowered, then it gets brighter when the turn element lights up. I can't see it being a grounding issue since the marker light shares a common ground with the turn and headlights and they're all on nice and bright.

This is really bugging me!

[gto4evr]

update to close out the post for future viewers:

decided to check the wiring diagram on 72 which should be the same and low and behold, it's completely different than the 71 diagram. What I'm seeing on the 72 diagram makes sense as to what's happening so mystery solved, Neither wire going to the marker light is a dedicated full time ground so when lights are on, one side is powered and the other gets a ground through the turn signal circuit, when the turn signal is on, that ground wire becomes hot to power the turnsignal bulb which is why the light goes out when the turn signal is energized. weird way to force the side marker to work both ways but there it is. simply a wiring diagram error. probably a hold over from 70 which also didn't flash like 69 didn't.