How to Determine if a Brake Light Relay is Required to Flat Tow a Vehicle

Updated 04/22/2024 | Published 12/15/2014

Question:

Will the brake lights continue to operate after 15-30 min of nonuse? Will they go to sleep after a period of time thus not requiring a brake light relay, but just a brake switch to operate the motorhome dash indicator light?

asked by: Will H

Expert Reply:

To determine if your 2014 Jeep Grand Cherokee will require a brake light relay like part # RM-88400 you need to answer the following questions:

Are you using a supplemental braking system that depresses the brake pedal in your towed car?

No - You do not need a brake light relay.

Yes - You may need a brake light relay. Continue on to the next question.

Do the brake lights on your towed car illuminate while the engine is off?

No - You do not need a brake light relay.

Yes - You may need a brake light relay. Continue on to the next question.

Do your towed car's brake lights act as both the brake signals and the turn signals?

No - You may need a brake light relay. Continue on to the next question.

Yes - Your towed car has a combined lighting system. You will need a brake light relay to ensure proper activation of its signal lights.

Does your towed car have separate brake lights and turn signals?

No - Your towed car has a combined lighting system. You will need a brake light relay.

Yes - Your towed car has a separate lighting system. You may need a brake light relay. Continue on to the next question.

Are you wiring your vehicle with a six-diode kit or a TowDaddy custom wiring harness?

No - You will need a brake light relay to ensure proper activation of your towed car's signal lights.

Yes - You do not need a brake light relay.

I attached an install video for you to check out as well.