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Trailer Hitch Plug

Trailer Hitch & Components

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Trailer Hitch & Components at 1A Auto

What are the trailer and towing parts and where are they located? 

Towing a trailer is a bit more complicated than just hooking the trailer onto a hitch and setting off.  The trailer needs to be hooked up to your truck’s or SUV’s electrical systems.  Once the trailer is hooked up, the trailer brakes and brake lights will go on when you hit the brakes, and the trailer signal lights will go on when you put on the blinkers.  That will help other drivers see what you’re up to and help you get yourself and your cargo safely to your destination. 

There are a couple of important parts that make the connection between the trailer and your truck.  A trailer hitch plug receptacle is where the wiring harness that carries power to the trailer brakes and lights connects.  It is usually attached to the trailer hitch or mounted near it on the bumper. 

The trailer brake control unit is what sends the signal to the trailer brakes to go on when you press the brakes in your vehicle.  It is usually mounted below the dash.  Some trailer brake control modules simply send a signal to apply the electrically operated trailer brakes.  The brakes go on at a pressure and with a time delay that the driver presets.  Others use a pendulum to measure the braking force the truck is undergoing, and adjust the signal to adjust the braking force at the trailer brakes.  

How do I know if my trailer and towing parts need to be replaced?         

If your trailer is losing sync with your truck, then you may need to replace one or more of the towing parts.  The contacts of the trailer hitch plug can corrode if it is left open to the elements or if moisture creeps in.  A bad connection at the plug might mean that your signal lights and brake lights don’t go on when they should.  That leaves other drivers guessing what you’re trying to do with that big boat or camper behind you, which is a stressful situation for them and you.  What’s worse is a bad connection might hinder the operation of your trailer brakes.  Then the trailer might start to sway when you hit the brakes.  If your trailer brake control module isn’t working, it, too, can cause the trailer brakes not to come on, or in some cases to stay stuck on.  You can check that the problem is with the control module and not the connector or the brakes themselves by checking the control modules output voltage with a voltmeter as you apply and disengage the brakes.  The control module should output 12 volts when you apply the brake and no voltage when the brake is off. 

Can I replace the trailer and towing parts myself?  

Installing towing parts is fairly easy.  Towing parts from 1A Auto replace the parts that came with your truck’s factory towing package.  Installing towing parts onto a truck that wasn’t initially set up for towing is a whole different story that involves splicing wires.  Replacing your failed factory towing parts is much more straightforward though. 

For a trailer hitch plug, you’ll just have to disconnect the wiring harness that runs to it and twist it out of the rear bumper.  Then you can twist the new one into place and connect the wiring harness. 


The process to replace a trailer brake control module is actually pretty similar.  Unbolt the control module from its position underneath the dashboard, disconnect the wiring harness, connect the wiring harness to the new control module, and bolt it on.  

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