Installing Brake Controller and 7-way Trailer Connector on 1991 GMC 1500
Updated 11/29/2011 | Published 11/26/2011
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Question:
Hooking up trailer, 7 pin, trailer breaks. Light hook up no problem. Power and ground in cab, also a no brainer BUT, that where my brain stops. Where exactly do I connect the others? Its a 1991 GMC 1500K.
asked by: Alan
Expert Reply:
From your question, it sounds like there is two wires on the brake controller, plus a few on the 7-way trailer connector you are not sure about, is that correct?
Take a look at our 4-pole to 7-way adapter, part # 37185. In addition to the lighting circuits, there are four additional wires. The white wire attaches to clean metal on the vehicle frame to provide a ground connection. The purple (or sometimes yellow) wire typically powers the reverse lights on the trailer (if it is so equipped). If needed, this wire would be tapped into the reverse light circuit on the vehicle. If not needed, the wire can be capped off and bundled up out of the way. The blue wire which carries the brake output voltage from the brake controller and the black wire that provides 12-volt power for any trailer mounted accessories would be extended and ran to the engine compartment. The blue wire would then pass through the firewall and attach to the blue wire coming off the brake controller. The black wire would attach to the positive battery terminal via a 40 amp inline circuit breaker like part # 9510.
This leaves the controller itself. The controller should be mounted under the dash within easy reach of the driver, according to the instructions included with the controller. The black wire runs to the positive battery terminal via a 20 or 30 amp breaker (controller instructions will state which is needed). The white wire is grounded to the negative battery terminal. The blue wire, as mentioned above, carries the output voltage from the controller and runs through the firewall and engine compartment under the vehicle to the trailer connector. The red wire would tap into the cold side circuit on the brake stoplight switch. The brake stoplight switch is located under the dash, at the top of the brake pedal. Follow the brake pedal up, until you can see the switch. The switch itself can have several wires exiting it. You will need to use a circuit tester like part # PTW2993 and test each wire until you locate the one that only shows voltage when the brake pedal is pressed. Once the correct circuit is located, tap the red wire from the controller into it.
I will link you to a few of our FAQ articles that will assist you with your installation.
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