Turn and Brake Lights Do Not Work Using 6-Diode Kit and Converter for Towing a 2012 Cadillac SRX


I wired this up as per instructions but the only thing that works is the tail/clearance brown wire lights. Neither the brake nor turn signal lamps, right or left work. What could I have done wrong? Cant believe all my connections are loose. Used 6 diodes as required. one for each tail, turn and brake light left and right. The ground wire from the converter was wired to a separate ground connection. self tapping screw into frame. Scaped away paint before connecting wire. The lights all work on the SRX without the connection to the M/H so fuses are not blown. I did install the #118158 converter in the front of the SRX rather than the rear since there was more room at the front. Is this a problem? ie longer length wire from the converter to the lamps The 2 way from the M/H turn signal and brake combined had already gone thru a converter within the M/H since the M/H wiring uses clearance, turn and brake light all on the same bulb but come separated out on the 7 way connector as a 2 way wiring. Could this be the problem? ie 2 converters Could the 118158 converter be bad? Help please.

Expert Reply:

It sounds like you have a good grasp on the installation of the Roadmaster 6-Diode Universal Wiring Kit, # 154-792-118158, and you have already gone through a few troubleshooting steps, so I would recommend troubleshooting the converter box from the # 118158 wiring harness.

Installing the # 118158 wiring harness at the front of your 2012 Cadillac SRX instead of closer to the tail lights is not a problem. To troubleshoot the converter box of this wiring harness, I would first recommend using a circuit tester like # 40376 and test the green and yellow wires for proper function on the input side of the converter box. This will tell us if the left and right turn and brake signals are reaching the converter box from the 7-way connector on the motor home. If the green and yellow wires are not working properly, then the issue is between the # 118158 converter box and the 7-way connector from the motor home.

If the wires are working properly on the input side, then you will want to move to the output side. Sever the green, yellow and red wires completely and test each wire for proper function with a circuit tester. As you may know, the yellow wire is for the left turn signal, the green wire is for the right turn signal and the red wire is for the brake signal. If you do not have a signal on the output side of the converter box, then the converter box will need to be replaced.

If the green, yellow and red wires on the output side of the converter box are working properly, then the issue will be further down. If this is the case, then I would suggest checking that the diodes are wired correctly and functioning properly. It would be highly unlikely, but if you ensure that the diodes are wired correctly per the diagram in the installation instruction and there is power going into the diode, but not coming out, then the diodes may need to be replaced.

If you follow these troubleshooting steps and are unable to find the cause of the problem or a solution, then let me know what you come up with and we can take further steps.

expert reply by:
John H

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