Trailer/Towing 7-Pin & 4-Pin Connections
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Joined: May 2007
Posts: 45
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From: Pittsburgh PA
Trailer/Towing 7-Pin & 4-Pin Connections
I am having some problems with the 4 pin and the 7 Pin Connectors at the hitch. I have installed Relay 05 (it was in the glovebox when I bought the truck) and have since checked fuses F105 F106 and F42 (found to check from other threads). The fuses are good and the relay was out of the bag, so to speak. I have no fucnctions at the pins though. I have battery power but no running lights, turn signals, brake lights, or the back up lights. What else should I be looking for? Could the relay be bad? Thanks in advance. 
Technical Article Contributor
Joined: Jun 2002
Posts: 10,511
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From: Under the flightpath of old ORD 22R
You are missing some fuses to check.
You have
F105 - brake controller power
F106 - trailer tow battery charge relay ( normally open contacts ).
F42 - Trailer tow left stop / turn lamp
You need to check
F36 - Trailer tow right stop / turn lamp
F10 - trailer tow parking lamps relay & trailer tow reversing lamp relay
F13 - trailer tow battery charge relay coil ( this should be Ok, you have battery )
How did you check the fuses ?
How are you checking the pins on the tow adapters ( could be a ground issue for what you are using on your meter ) ?
You have
F105 - brake controller power
F106 - trailer tow battery charge relay ( normally open contacts ).
F42 - Trailer tow left stop / turn lamp
You need to check
F36 - Trailer tow right stop / turn lamp
F10 - trailer tow parking lamps relay & trailer tow reversing lamp relay
F13 - trailer tow battery charge relay coil ( this should be Ok, you have battery )
How did you check the fuses ?
How are you checking the pins on the tow adapters ( could be a ground issue for what you are using on your meter ) ?
Senior Member
Joined: Dec 2007
Posts: 358
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From: NW Montana
In NO way can I be considered to have any worthwhile knowledge of anything electrical, 
but while reading the instructions that came with my extra relays for the 7 pin I thought it indicated that a brake controller needed to be installed in order for the circuit to be completed. In other words, you won't have complete functionality at the plug on the bumper until all parts (controller) is/are present.
SScully, I may be wrong here. If so, please correct.
but while reading the instructions that came with my extra relays for the 7 pin I thought it indicated that a brake controller needed to be installed in order for the circuit to be completed. In other words, you won't have complete functionality at the plug on the bumper until all parts (controller) is/are present. SScully, I may be wrong here. If so, please correct.
Technical Article Contributor
Joined: Jun 2002
Posts: 10,511
Likes: 10
From: Under the flightpath of old ORD 22R
Brake controller is only for the trailer brake circuit on the 7 pin trailer tow adapter.
All the other pins work without this installed ( I have my Truck-Lite back up LED lamps installed on the 7 pin trailer tow reversing circuit ).
Think of it this way, the 4 pin trailer tow adapter does not have a provision for the brake controller, and it has the parking lamps and L&R Stop / Turn lamps on it.
All the other pins work without this installed ( I have my Truck-Lite back up LED lamps installed on the 7 pin trailer tow reversing circuit ).
Think of it this way, the 4 pin trailer tow adapter does not have a provision for the brake controller, and it has the parking lamps and L&R Stop / Turn lamps on it.