I've had the "R LAMP" message on my GTA's instrument cluster for months, and it dawned on me tonight that it might be because I'm running one of GTAuto's 4th gen spoilers that uses an LED brake lamp system instead of the incandescant bulbs. If I am correct in my assumption that the status of the bulbs is checked by sending a small voltage through the system, the LED brake lamp could be my problem. An LED has an ultra-high resistance at voltages below the turn-on voltage level, so I may need to parallel a resister of appropriate voltage. Then I'll just have to figure out how to keep it from sinking the full 12 volts (or close to it) when the brakes get put on.

 

Couldn't you simply splice in a conventional incandescent bulb, and hide it in an invisible location? It's not an elegant solution, but it should work perfectly. You'll just have to replace that bulb every now and then.

 

That's an idea, but I'd need to parallel-wire however many of them were in the original housing (which might only be 2). I suspect that rigging those up so that the heat won't effect its surroundings might be more trouble than wiring up a small circuit.

 

You do have a point; it would be a hassle to hide the bulbs in a place where heat wouldn't be a problem, but you could still replace them easily.

Perhaps it would make more sense to do this: Use a multimeter to measure the DC resistance of one of the stock light bulbs. Perform the necessary match to determine the resistance of all of the stock bulbs in parallel. Purchase and install a large resistor of the same value, in parallel with the LED brakelight.

 

You could also buy a potientiometer and splice it into the light harness. Once you adjust the resistance so that the warning goes away, use a resistor of the value instead of the pot.

 

find the amperage and voltage of your LED's. Then use the formula Vt-Vl/Al Total Voltage going into system (Usually around 14) - the Voltage requirments of the LED/THe amps of all the LED's added together. That will give you the Appx value of resistor to use in series with the line.

 

To elaborate on what Chris said. You can’t really check them like that. As a light bulb filament get hot the resistance goes up. So you would have to measure the currant with the light on then calculate the resistance hot. Then use a resistor of that value or go up to a common value. But I would try a 470 ohm 1 watt resistor first. This should get that little idiot light to go off. If not try a 220 ohm 2 watt resistor. Good luck.