'92 GTP, LED upgrade issues with turn signals

[crazyd]

Hey all,

Years ago I worked my way through an LED upgrade to all the cars that needed it. When I did the GTP I guess I stopped at the turn signals and forgot why, so I gave it another go.  The sidemarker ones in the bumper were already done, as well as those in the rear taillights, and I had upgraded to the Astro flasher solenoid to deal with the hyperflash.  But I had left the incandescents in the front and still had hyperflash. 

So I ordered a set of switchbacks from Amazon and put them in, only to find out why I hadn't before: they stop flashing when I hit the brakes. 

I had also found out the hard way that replacing the CHMSL bulbs with LEDs trips the ABS computer into an error condition that it thinks they're burned out, so I can't replace those either.

Has anyone found a solution to this?  Is there a switchback bulb that works for retrofits like this?

[crazyd]

Yeah, I already topped up the blinker fluid

[Schurkey]

40 minutes ago, crazyd said:

Has anyone found a solution to this?  Is there a switchback bulb that works for retrofits like this?

Yes.  Throw the headaches in the trash, switchback to the correct bulbs.

Edited January 13 by Schurkey

[GnatGoSplat]

I tested switchbacks in my 89 Cutlass.  Got them free and was under obligation to test them in something.  They exhibited some odd behavior.  Can't remember exactly what they did wrong, I think the bright (amber) filament would come on with the park lamps and they wouldn't blink.  Anyway, I tracked it down to GM's unusual system where they used a single filament bulb in the sidemarkers which ground through the turn signal bulb.  This allowed them to save money by not using a dual filament bulb in the sidemarkers and it also does that neat alternating trick at night, where when the lights are on, the front and sidemarker bulbs flash alternately, but during the day with lights off, they flash in unison.

Long story short, the solution was to replace the little sidemarker bulbs with LED bulbs.  Being diodes, this would block current flow when the park lamps were on,  which made the switchback bulbs in the front turn signals work properly.

Your GTP is likely wired similarly.

 

[pwmin]

The red GP with switchbacks worked fine (I know, wrong generation), but the black one only the right one comes on when remote started.  I went to single "filament" white LED's, but I was annoyed by the indicator arrows showing up green all of the time.  The red one does have aftermarket assemblies, though.

[crazyd]

7 hours ago, GnatGoSplat said:

Long story short, the solution was to replace the little sidemarker bulbs with LED bulbs.  Being diodes, this would block current flow when the park lamps were on,  which made the switchback bulbs in the front turn signals work properly.

Already did the sidemarkers with LEDs. 

[GnatGoSplat]

31 minutes ago, crazyd said:

Already did the sidemarkers with LEDs. 

Sorry, didn't catch that the first time.

Only schematic I have is for the Cutlass which has combination stop/tail/turn for the rear bulbs, so it's going to be a bit different.  Might try reversing some of the bulbs.  They're advertised as being able to work any direction, but I actually had some work one direction and not the other.

[crazyd]

Maybe I was too wordy.  TL;DR is the front turn signal LED switchback indicators work, they just stop flashing when I get on the brakes.