Wanting to add additional brake lights... Can I just tap the existing circuit?

[Fredrickson]

I want to add another set of brake lights to the truck, but I read changes in the resistance of the brake light circuit can affect torque converter lockup.

Is the lockup issue only when a bulb is burned out or missing, or will additional bulbs also affect the circuit?


As far as a solution:

Can I tap directly into the existing tail light's wiring and add the lights in parallel?

Should I use a 12v relay to trigger the additional light?

or should I get one of those trailer light conversion kits?

Or is there another, better method I am completely overlooking?


Thoughts?


This is on a 1994 E350

 

[MtnHaul]

The only "resistance" related brake light info I am aware of has to do with the RABS system. Basically if there isn't enough resistance in the brake light circuit the "brain"(?) seems to think that the tail lights are out and at 36-37mph the ABS light comes on and the RABS is deactivated. Lots of small skids during wet weather. My issue was caused by the LEDs on my flatbed as they draw so little so I had to wire in a resistor to the brake light circuit and problem was gone.

If you are still using standard bulbs then I would assume you are ok to add more. If you're just adding I would advocate for LEDs since they should last much longer than standard and since they draw so little it should be safe to just tap into existing wiring.

 

[franklin2]

Have at least one set conventional bulbs, and you can use conventional or LED for the additional bulbs. You need to load down the circuit with the current that a conventional bulb draws. You run into trouble when you use only LED lighting.

 

[ifrythings]

Highly recommend you do NOT add lights onto the factory wiring, these trucks have enough issues with switches burning up from just the stock lights I wouldn’t add anymore to it. Use the relay and run a separate fused wire from the battery for your lights.

 

[Selahdoor]

I ran a 10ga wire to the back of my truck. Directly from the battery. Fused at the battery.

I put a relay on that, in the back.

I added some good LED backup lights, and powered them from that relay. Switched the relay with the existing backup lights.

Later I needed a third brake light on the canopy. So I added another relay to the 10ga wire that I had run back there. Switched the new relay with the brake lights. And ran the third brake light from the relay.

10 gauge should supply all the power I could need for several relays, and light systems.

And the 'extra load' put on the existing system, by using it to switch the relay, is almost nothing.