GMT800 LED taillight & 3rd brake install kills cruise control

[someotherguy]

Hmmm...tried to word that subject so it would be easily searchable. I'll try to include enough different keywords in here so that helps, too.

Anyway subject is a 2006 Silverado SS that I installed aftermarket LED taillights (full replacement, not just LED bulbs in the factory sockets) and LED 3rd third brake light (CHMSL) at the same time.

Problems:

1. Cruise control no longer works. Switch on, press button to activate, nothing at all - indicator doesn't light up or flash or anything on the dashboard, and no cruise function.

2. Aftermarket remote start (Viper) no longer allows me to "remote start" with engine already running - now if that sounds funny, consider this: normally, you can take your running vehicle and press the remote start button to re-engage that mode, then take the key out. This allows the vehicle to keep running while you exit, and can lock/arm the alarm with the remote. Very handy to do something like run back inside the house for a moment or whatever.

OK. I read a bunch on the web about this and there are some well-meaning but very wrong theories on what may be causing it. I already have an LED-compatible flasher unit (Novita LM487) which cures any hyperflash you would get from LED lights in the turn signals. Also, on a GMT800 the signals and brake lights are separate circuits, so LED's in the signals are not an issue for the cruise, remote start, etc.

A few people did touch on the topic that the LED third brake light was causing the problem, and this is 100% correct. While cleaning the garage today I found my OEM piece and installed it, leaving the LED tails in place. My cruise works again and I can do the remote start trick again, too.

Crazy thing is my LED third brake light from VIPMOTOZ came with a large square module that ties in with the wiring, presumably it's a load resistor meant to cure this very problem, but unfortunately does not. Either it's rated incorrectly, wired incorrectly, or simply defective.

I'll be experimenting more with this in the coming days so I can get the LED piece back in place. I suspect it'll just be an issue of properly wiring a load resistor with the correct rating, and I'll share results as I go along.

Richard

[Distracted]

I will be watching this post. I also just ordered a LED third brake light from VIPMOTOZ.

 

Thanks

[someotherguy]

Solved it today and it's definitely a resistance issue. Added a 50 watt / 6 ohm resistor to the CHMSL circuit and this fixed the cruise issue and the related issue with the remote start. The wires I tapped into were the ones right at the plug for the light, using the black and light blue wires - the light blue appears to have a tracer, maybe tan or orange, couldn't tell for sure. The other wires are orange and blue with a white tracer so it's easy enough to tell them apart.

I used the resistor typically sold as a "load resistor for LED's" as it's contained in a large finned aluminum heat sink with tabs for mounting screws. I picked a spot on the sheetmetal support behind the CHMSL, towards the passenger top corner, hoping to be able to keep the wiring away from it. Drilled pilot holes using a piece of tubing scrap as a guard on the bit as you don't want to punch through more than just a tiny bit; the headliner board is sitting right against the other side of that sheetmetal. Applied some heat sink compound to the back of the resistor and mounted it up.

Oh, and the module that comes with the light from VIPMOTOZ is unrelated to the CHMSL. It's got something to do with the cargo lights as when I tried them with the module unplugged, only 2 of the LED's lit up. When I plugged it back in, all of them came on.

Richard

[Distracted]

What exact load resistor did you get and from where?

 

Thanks

[someotherguy]

As mentioned, 50 watt, 6 ohm - pretty much everyone has 'em. I've even seen this style at the local auto parts store but they charge at least double, if not triple what they cost elsewhere.

 

Examples -

https://www.superbrightleds.com/moreinfo/flashers-load-resistors/led-light-load-resistor-kit-led-turn-signal-hyper-flash-warning-fix/190/831/(only $5)

http://shop.advanceautoparts.com/p/sylvania-led-load-resistor-loadrbx2/11137849-P(way too expensive IMO)

 

Or just go to Amazon and enter 50w 6ohm in the search bar and you'll get nearly a thousand results, some for around $4 w/free Prime shipping. Just be sure you get the ones with the wires already attached unless you feel like soldering some wire to them as well.

 

Richard