Power Fuse Blows on T-One Vehicle Wiring Harness # 118544 When Running Lights are Engaged

Question

Question:

I recently purchased a T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part number 118544 for a 2012 Chrysler 300. It installed just fine, but when I went to test it the Tail light wire for the trailer didnt work. The turn signals did. I then removed the fuse from the yellow wire that goes to the fuse box and replaced it. The trailer light wire became live. When I turned the headlights off and back on, the tail light wire was dead until I once again removed and replaced the fuse. I have a few questions: 1. Do these symptoms indicate there is a problem with the wiring harness? 2. The directions said to hook to the wire coming to the fuse box. This connection is always on. Should I find one that only comes on with ignition? 3. Is there any chance that if this harness is hooked up to an always Hot connection that it will run the battery down over time? Thanks

asked by: Bob J

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Expert Reply:

The two most likely causes for the blown 12V power fuse that feeds your TowReady T-One Vehicle Wiring Harness # 118544 are a short within the trailer wiring for its running light circuit or excessive current draw from the clearance/marker lights on your trailer.

If you happen to have access to either another tow vehicle or trailer you can try substituting one in place of yours to see if the issue remains. This is the easiest way to isolate the fault to either the vehicle or trailer.

If you have a circuit tester such as the # PTW2993 you can test the pins on the T-One harness 4-pole connector with your trailer disconnected. You can have a helper activate the taillight function on the vehicle while you apply the tester to the 4-pole. Please refer to the photo provided which shows where to ground the tester and apply the probe for the running light circuit. If you detect a correct steady signal when the vehicle lights are on (and no fuse blows) then you know the issue is in your trailer. If there is no running light signal at the 4-pole and the vehicle running lights work properly then the converter may be damaged.

Next you can move on to the trailer. With your trailer disconnected from the harness, trace the trailer wiring for the running light circuit (this will usually be the brown wire) from the connector at the front of the trailer all the way back to the running lights. (Also check that the white ground wire is affixed to a clean metal surface.) Inspect the condition of the wire insulation all along its length, paying particular attention to points that bend and that might touch the trailer frame. Even small cracks or wear spots in the insulation can lead to a short; if any parts of the running light wiring show damage repair them with electrical tape or replace the wire. Also, if any of the wiring is loose it is a good idea to secure it to the trailer frame with zip ties to help prevent future damage from abrasion. Next check the tail light wiring at the lights themselves to be sure there is no damaged, loose or pinched wiring there.

The other possibility is that the clearance/marker lights on your trailer are drawing too much current through the harness causing the fuse to blow. If additional lights were added to your trailer or if they are all the incandescent type rather than the more efficient LED-type then there may simply be too much current demand. This harness is rated to deliver 5.6 amps to the running light circuit. This capacity must feed all of the clearance/marker lights on the trailer.

It is important to follow the manufacturer installation instructions, including that for the 12V power connection. The harness will not drain your battery since it only draws significant power when the lighting functions on your vehicle are activated.

expert reply by: Adam R

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