LED Tail light/Turn Signal conversion

[truckintim05]

I work at a truck upfitter shop, where I've been working on a 2020 GMC 3500 flatbed.  The truck had an OE pickup bed on it which I removed. This truck had incandescent tail lights, however the flat bed has all LED lighting. I'm plenty familiar with using load resistors on the circuits to stop the "hyperflash" issues. In the past few months I've installed plenty of flatbeds on the 2020 HD Chevys. Typically I can use two 50w 6ohm resistors wired in parallel on each turn signal circuit to stop the hyperflash. That is not working on this particular truck. I'm not sure if there is some difference between the GMC and the Chevy circuitry, or it's something else entirely. I tried adding two more per side, which measures about 1.5ohms total. Seems like a lot of resistance, but aparently it's futile (yeah I said that) as I still have a hyperflash. Any 12V nerds out there that can give me any ideas?

[carkhz316]

I have encountered this a few times. I don't know why it is, but I feel like the big resistors are barely within a tolerance of what the vehicle expects to see for a voltage drop across a particular turn signal circuit, hence the fickle behavior. The last one I encountered, I ended up wiring a third resistor to one corner, so that I had the two in parallel and the the 3rd one in series to one of the first two. I only had to do this to one corner for whatever reason, as it was just the one corner doing it. It effectively made that corner ohm out at 9 ohms instead of 3. It cured the hyperflash in this instance.