Installation of Brake Light Relay on 2017 Jeep Cherokee with SMI Stay-In-Play DUO Braking System

Question:

We ordered the SMI Stay-In-Play Duo Braking System SM99251 for our 2017 Jeep Cherokee Trailhawk. For the Tail Light wiring we got the Hopkins Kit HM56208. From the description we needed a Brake Lite Relay Kit, so we got the Roadmaster RM-88400 kit. I am getting confused about the wiring of the Brake Lite Relay Kit in combination with the Braking System. How are they both connecting to the brake pedal switch of the car? I am unclear of the sequence and best point to tap/intercept the wiring of the car. Could you provide some clarification? Thanks in advance

asked by: Frank D

Expert Reply:

On the brake light relay, # RM-88400, the monitoring wire from the SMI Duo # SM99251 and the green wire from the relay attach to the brake switch wire on your 2017 Jeep Cherokee (unless it has push button start which I will cover next). Basically what you are doing is installing the relay in line with the brake switch wire.

So you have the brake light switch on your 2017 Jeep Cherokee. You have identified the cold side wire. You cut that wire several inches down from the switch. Then you take the 2 ends of the wire you just cut along with the SMI monitoring wire and splice them to the green wire with blue butt connector on the relay.

The black wire from the relay will splice into the brake light wire on the Jeep a few inches back from the actual brake light. Red is the power wire and white is ground.

If your Jeep has push button start the process is different. The SMI Duo monitoring wire and brake switch wire is the same as above except instead of attaching everything to the green wire you will attach it to the blue wire that goes to the 87A terminal of the relay. The black wire is the same, white is the same. Red will attach to the brown wire from the tow bar wiring harness you are using. This means that the RV running lights have to be on all the time for the relay to work.

It is possible that you will also need an additional diode # RM-790. To see if a diode has been installed on the towed vehicle's tail light wire, or if one is needed, start the engine and turn on the headlights.

With a volt meter, test the tail light wire for 12 volts at any point between the splice you made for the relay red wire and the tail lights. If there is no voltage a diode is not needed. If it does show voltage a diode is needed. The diode will install after the spice from the red wire and before the tail lights on the vehicle.