Original Side Marker Operation

[Six862m6]

Guys,

I'm working on my front park/turns and side markers and I have a question on trucks that had factory operational side markers. My truck is a '68 which would have had reflectors only but the wiring is updated to include side markers.

Here is my question: on trucks that came with factory lit side markers, did only the fronts flash with the turn signal (opposite to the turn signal) or did the rears also flash?

I'm working on updating my front park/turns to a switchback style LED bulb (installed new clear lenses instead of the factory oranges) and I have a brand new AAW front light harness for a slightly later truck (lit side markers, which my truck had been modified for this before this). The factory wiring is NOT going to play nice with LEDs in the front park/signal location though. I've tried everything, including inline resistors but at this point my options are to either give up the idea of switchback style bulbs upfront and return to orange 1157 incandescent bulbs or rewire the front side markers with some trick relays so that they function like original (I did this with my front bumper fogs recently so that they work like a modern car; the switch won't turn them on unless at least the park lights are on, the switch will turn them off though, and when the high beams come on they automatically switch off).

That being said, I'm not going to run the extra wiring for all this if the rear side markers flashed from the factory also and I'm just looking for a definitive answer on this.

[Ol Blue K20]

Only the front markers. I believe it blinking was a 71,72 thing.

[Six862m6]

Originally Posted by Ol Blue K20

Only the front markers. I believe it blinking was a 71,72 thing.

Interesting, so 69 (when optioned with) and 70 didn't blink? Anyone else confirm on this?

[DDassow01]

My 70 GMC is original and they do not flash.

[70STOVEBOLT]

Yes, my 70 did not blink, and I bought a factory front light harness out of a 72 and it now blinks.

[MySons68C20]

On my 68 the fronts did not flash from the factory. They were reflectors only.
Once I installed the AAW harness I updated to the flashing front side markers.
The backs only function as a marker only (no blink) once the light switch is pulled.

[Accelo]

To get the blinkers to flash on when the side marker is off and the side marker on when the blinker is off the polarity is switched back and forth. So, nothing you can do, using the LED's, will fix this. As you know the LEDs require a positive on a certain terminal to function.
Now I am not certain how your particular truck is set up. But this is true for some of the trucks. I do like how the factory switched the lights on and off and considered attempting to incorporate it into my 70. I decided I liked the LED more than the alternating lights feature.
I am confident you will need to use the incandescent lamps for that feature to work.

[zosoppp]

There are 194 LED bulbs that are polarity independent, meaning they work with either polarity.

These are the ones I got for my 1970 rewire project:

https://www.superbrightleds.com/more...t-car/197/850/

They have them in various colors, including red and yellow for the side markers, for the 194 socket.

I have verified on my bench that they work with either polarity.

[Six862m6]

Originally Posted by zosoppp

There are 194 LED bulbs that are polarity independent, meaning they work with either polarity.

These are the ones I got for my 1970 rewire project:

https://www.superbrightleds.com/more...t-car/197/850/

They have them in various colors, including red and yellow for the side markers, for the 194 socket.

I have verified on my bench that they work with either polarity.

Good info to know and these should come in handy! However this won't solve my particular issue. If anything at all is in the front side marker sockets, even an incandescent, it causes the park/turns to activate the wrong circuit (orange instead of white) for the parking light feature.

[Six862m6]

Originally Posted by Accelo

To get the blinkers to flash on when the side marker is off and the side marker on when the blinker is off the polarity is switched back and forth. So, nothing you can do, using the LED's, will fix this. As you know the LEDs require a positive on a certain terminal to function.
Now I am not certain how your particular truck is set up. But this is true for some of the trucks. I do like how the factory switched the lights on and off and considered attempting to incorporate it into my 70. I decided I liked the LED more than the alternating lights feature.
I am confident you will need to use the incandescent lamps for that feature to work.

Well, I know I could get it done (all LEDs) using some relays and custom wiring but after learning that only 71/72s blinked from the factory, I think I may just do a simple modification to the side marker socket wiring for them to stay solid and call it a day. As far as how my truck is setup, it has a new AAW front light harness (as well as engine harness and main dash harness) that is unmodified. I have a headlight relay harness hooked to it to take the headlight amperage off the light switch and two splice in wires for the fog relay signal off the parking lights and high beams and that's it.

I'm not even going to cut into the marker light wiring to correct this issue; just going to leave the sockets open, cut the old sockets off my old harness and quick splice the power wire to the original sockets' power wires and the grounds to the body like they were before.

I'd like the flashing feature as well but it would mean even more custom wiring and relays in the engine bay and I think I'd rather just not.

[Six862m6]

Thanks to all for chipping in on their original trucks and how the side markers functioned from the factory!

[Six862m6]

A final update on this post as to what I ended up doing on my truck.

I ended up using the front side marker sockets/wires from my old harness (were added on at some point to the original '68 harness anyway) and connected the power side to the power side of the new front light harness side marker socket via a quick crimp and connected the ground side directly to the body via some ring terminals. Left the bulbs out of the sockets on the new light harness. I did it this way so none of the new harness's wires were actually cut. Then I installed a couple of new LED flashers for the turn and hazard circuits. All is well now. All side markers work (all LEDs, no flash in the front of course, but I decided this was ok since only '71 & '72s flashed anyway), front parking and turns work (LED switchback style so they are white during park function and orange on turn signal function), and rear tails/brake/turns work proper (Also LEDs).