Ballast Resistors

Hello, I am relatively new here and not quite sure how to pose this question so here goes. I have a 78 GMC High Sierra 3/4 ton camper special P/U. 454 ci, auto, 2 wheel drive. The truck was basically given to me so I dont know that much about it. There is a ballast resistor mounted on the firewall in the normal place but the wires from either end have been cut. Where do these wires connect to and what is the function of this resistor. Thank you in advance for reading and hopefully replying.

Hello, I am relatively new here and not quite sure how to pose this question so here goes. I have a 78 GMC High Sierra 3/4 ton camper special P/U. 454 ci, auto, 2 wheel drive. The truck was basically given to me so I dont know that much about it. There is a ballast resistor mounted on the firewall in the normal place but the wires from either end have been cut. Where do these wires connect to and what is the function of this resistor. Thank you in advance for reading and hopefully replying.
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I had a 77 camper special and it had trailer brakes controller but an older style.
The resistor was a slider adjustable type for setting the amount of brake application you got on the trailer.
Bob B

Thank you, This truck has trailer brakes as well but were ad on. The controller is in the cab and is of the modern style. This resistor seems to have been in place since the truck was new and also holds the ground strap that goes to the hood. Like I said the wires are there but have been cut off so I have no idea where they are supposed to go. I heard mention of one wire to the coil but its in the distributor cap so im a little confused on how and where to connect this thing.

Thank you, This truck has trailer brakes as well but were ad on. The controller is in the cab and is of the modern style. This resistor seems to have been in place since the truck was new and also holds the ground strap that goes to the hood. Like I said the wires are there but have been cut off so I have no idea where they are supposed to go. I heard mention of one wire to the coil but its in the distributor cap so im a little confused on how and where to connect this thing.
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Maybe the previous owner replaced an older brake controller and didn't bother to remove the resistor.
Is is quite large and has a slider on it to adjust it?

BTW GM hasn't used a separate resistor in the ignition for many years. the resistance is built in to the wire to the coil with a separate wire from the starter solenoid to bypass if during starting for a hotter spark at that time.

Bob B