I tried switchback LEDs, both random Amazon brand and Diode Dynamics, and they are always yellow. Never white like they should be when on as parking lights. I am talking about the turn signal bulbs in the headlights by the grill. They are 2057 bulbs.

I've done some multimetering and some stand-alone voltage regulating.

On as parking lights:
Pin A has 10v
Pin B has 12.5+ (running system voltage)

When turn signal is on:
Pin A cycles between 12.5+ and 2 volts
Pin B has 12.5+

With the voltage regulator and the LED in hand, the only way to get the white light is when only pin B has voltage. If both pins have voltage, it is yellow. Even when they both have just 10 volts. Seems like I need to get down below 7 volts before nothing lights up.

So to make the LED switchback like it should, I would have to block the voltage above 7 volts to pin A while the parking or headlights are on, but allow voltage to pin A when the turn signal is on.

How would I accomplish that?

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WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

What would happen if you used Ohm's Law and add resistors to get the resistance and current back to what circuit B would be as a 2057 Bulb?

I'm assuming the measured voltages were with the LED installed.

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Info on dropping a 92-99: Here.

I think the parking lamp power and turn signal power comes from different paths. I think if I snip the parking lamp power circuit (pin A), the LED will work as intended. I think that will also set off the bulb monitor. I think I can fix that by putting in a resistor to ground on the snipped circuit. I think maybe putting a resistor inline with that circuit instead could also work. I think I need to look at my FSM.

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WHITE WHINE - 1992 SSE Supercharged 236.26 ci (.040 Over) 15.090 at 90.2 MPH on old engine w/ slipping trans & melted O2 sensor - Gen 3 M62 and matching TB, Gen 2 Pully, Zillamotorsports Ported LIM, YT 1.72 Roller Rockers, SII FPR & Injectors, Hypertech Thermomaster chip w/ 160 Thermo, TransGo Shift Kit, Infinity/Pioneer Speakers & a 10" Alpine Type R Sub, all the watts, 140 amp Alternator, Ricepipe CAI w/ heatshield, Pilot Angel Eye Foglights, Clear Corners, '02 17" Chrome Bent 5's, Magnaflow F-Body Muffler and Hi-flo Cat, Ceramic Coated Ported Exhaust Manifolds, Fan Override, Monroe Reflex struts, red calipers
2009 G8 GT - Sport Red Metallic, loaded, SOLO Axlebacks, Rotofab Intake, Tuned, autodim mirror, removed intake manifold cover, HSV GTS triple gauge pod, two tone red-hot shifter and HSV SuperSport steering wheel, GXP rear sway bar and diffuser, 3.45 diff and various Camaro suspension bits, LED Taillights

I've just quickly cycled the power switch for the light I have them on. I have switch backs in the fogs on the Caddy. A quick cycling of the fog light switch, switches them.

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Retired Bonneville Owner and former GM Tech:
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