License plate LED bulb upgrade

[-=Jeff=-]

No the flasher will not fix it but will be needed. The problem is the way the side marker and park/turn bulbs are wired


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[ZR1North]

Originally Posted by -=Jeff=-

No the flasher will not fix it but will be needed. The problem is the way the side marker and park/turn bulbs are wired


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Ah, I'll delve into the wiring diagrams further as well.

[-=Jeff=-]

Originally Posted by ZR1North

Ah, I'll delve into the wiring diagrams further as well.

I will save you the hassle. The side markers run 12v in both directions. Parking lights off, when turn signal is on the side marker is also on. Parking lights on the voltage travels the opposite way and when the turn signal it on the side maker turns off (opposite).

I have not really looked to see what can be done to keep the function the same.


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[ZR1North]

Originally Posted by -=Jeff=-

I will save you the hassle. The side markers run 12v in both directions. Parking lights off, when turn signal is on the side marker is also on. Parking lights on the voltage travels the opposite way and when the turn signal it on the side maker turns off (opposite).

I have not really looked to see what can be done to keep the function the same.


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Thanks Jeff - great analysis; no wonder the flashers and signal lights were erratic when I tried the LEDs in the front park/signal light sockets. I am going to delve into this further as well. Looks like some digital switching circuitry (to address the AND-OR functions) might be required between the lights and the control signals.

[-=Jeff=-]

This is from an 88, probably the same in later years but maybe not

GM used the filaments of the bulbs to their advantage, if I apply 12v to both sides of the bulb it will be off, but with LEDs that does not work, since the Bulb is basically a short, the new LEDs are not.

IF I were to place the LED in the front of my car and remove the front Side marker it will work in both cases

I have a 2 relay (per side) solution which might be the best I am going to get. it will change the wiring of the marker light and a ground will need to be added, But it would work.

Also in current OEM state, if you put LEDs in the front side marker, they will only with parking lights OR Turn signals, not both ( due to GM Design)

[XfireZ51]

Jeff,

I've seen LED bulbs for signal and tail lamps at AutoZone. Was tempted to try them when I did the Euro lamp conversion but w 8 bulbs needed it was going to be a bit pricey.

[ZR1North]

Originally Posted by -=Jeff=-

This is from an 88, probably the same in later years but maybe not

GM used the filaments of the bulbs to their advantage, if I apply 12v to both sides of the bulb it will be off, but with LEDs that does not work, since the Bulb is basically a short, the new LEDs are not.

IF I were to place the LED in the front of my car and remove the front Side marker it will work in both cases

I have a 2 relay (per side) solution which might be the best I am going to get. it will change the wiring of the marker light and a ground will need to be added, But it would work.

Also in current OEM state, if you put LEDs in the front side marker, they will only with parking lights OR Turn signals, not both ( due to GM Design)

I took a look at my 91 wiring this evening, and I see what you mean about the dual-side use of 12V. It's another example of how GM used bulb filaments for circuit control, a little like what they did with the fog light disable when switching from low to hi beam. I see how a couple of relays could solve the switch to LEDs for the front signals and side markers. I'll have to sleep on it - just did a relay mod to address the issue I had with fitting the HID fog lamps and need to tackle some other (non Zee) things on my to-do list before getting the wire strippers out again.