Left Turn Signal Circuit Causes Power to Bleed Over to Brake Circuit on 2006 Ford F-350
Question:
I have a 2006 F-350 Lariat with a integrated TBC. My problem arose when I bought a used new to me 5th wheel. I hooked it up and shortly after towing it I get a TCB Fault display on my dash, followed by a Trailer Disconnected, and I had No trailer brakes. When I got the new 5th wheel home I disconnected it from the truck. However with the 5th wheel disconnected, when I start the truck the TCB Fault would display on my dash followed by Trailer Disconnected. I took the truck to my mechanic and he put it on his OBDII and it did not show an error code. I bought a used OEM TBC and took out the original one and installed it. I started the truck and I did not get a TBC Fault on my display so I thought all was good. No such luck. I tested the 5th wheel and found that the brake wire and the 12V wire were switched on the 5th wheel plug. I believe that is what ruined my original TBC. So now with my new OEM TBC installed I checked the Truck trailer receiver plug and found out that Now when I push the brake pedal on the truck i get 13VDC on the electric brake wire Blue But, I also get voltage to the Left turn and reverse posts. Can you please tell me if this is because the replacement TBC is bad? Or can the TBC cause power to bleed across lines? I have replaced Both sockets on the Truck and on the 5th wheel. I no longer have the 7 pin socket on the bumper. When I bought the truck I relocated the receiver plug to the bed. I have taken the socket off and just have bare wires so I know its not the receiver socket. I went out this morning and disconnected the on board TBC. Now when I test the wires my right turn signal does not bleed over to other wires, but the Left turn signal bleeds over to the brake blue wire but no other wires. I have taken off the wire loom off the all the wires from the plug to where the wires T under the belly of the truck. I found a wire that is labeled Center High Mount Stop Lamp the wire is not connected to anything. Can you please tell me what that goes to? Thank you for your help.
asked by: Ralph H
Expert Reply:
First, the center high mount stop lamp or CHMSL powers a third brake light. There is one under the truck for a camper shell that has a third brake light on it.
To me it sounds like there is a short somewhere, wires exposed and touching other wires, which is causing the back feeding. It is likely a problem somewhere that is difficult to access or I imagine you would have found it by now since you have done so much already.
What I recommend is to bypass the trouble circuits since they are not wanting to be found and fixed. This is actually going to be pretty easy since your 2006 Ford F-350 has the brake lights and turn signals combined on the same circuit. All you will need to do is splice in a wire to the left turn signal/brake light wire behind a tail light on the truck and run the other end to the back of the 7-Way to the 3 oclock position. you can use a quick splice connector such as # SWC501746-1 and wire # 16-1-1 which is sold by the foot.
It is hard to say if your new TBC is damaged or not. I imagine that once the back feeding is fixed then it will work as it should. The other option is to install an aftermarket controller such as the P2 # 90885 with wiring harness # 3065-P. This will cause a fault to appear on the dash which can be removed by the dealer.
Products Referenced in This Question
Tekonsha Plug-In Wiring Adapter for Electric Brake Controllers - Ford
- Accessories and Parts
- Trailer Brake Controller
- Wiring Adapter
- Plugs into Brake Controller
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Tekonsha Prodigy P2 Trailer Brake Controller - 1 to 4 Axles - Proportional
- Trailer Brake Controller
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- Automatic Leveling
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Self-Stripping Connector with Waterproof Sealant - 14-18 Gauge - White and Blue - Qty 1
- Wiring
- Wire Connectors
- Quick Splice Connectors
- 18-14 Gauge
- Spectro
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Product Page this Question was Asked From
Ford Replacement OEM Tow Package Wiring Harness, 7-Way (Super Duty)
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- 7 Round - Blade
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