How to test 7-pin wiring?

[DaveR]

I just installed a new brake controller and a 7-pin wiring harness. I'm planning to buy a pop-up at the end of the season, so I don't actually own a trailer yet. Is there any way to check my work without a trailer? Or do I just wait until I buy one, and test it out then?

Thanks very much for the help!

[jroden]

there is a test box that places use who do this sort of thing, but you can do it yourself with a 12 volt test light following the pinout on the link below. If you have a helper it should go in a jiffy:

http://www.etrailer.com/faq-wiring.aspx

They also sell a ready made tester you can purchase:

http://www.etrailer.com/Tools/Tow-Ready/TR20117.html

And if you are adding it to a known good flat 4 wire you already were using, you just have to check the charge line from the battery and the blue wire you added from the brake controller.

Now that I think about it, though, I'm not sure how to test the function of your brake controller without a load attached. This forum here is pretty active and has people who can address these questions very quickly:

https://www.rv.net/forum

[DaveR]

Thanks very much, I appreciate the help!

[brian_bp]

Now that I think about it, though, I'm not sure how to test the function of your brake controller without a load attached.

Most controllers are voltage-output devices, so (for instance) at half-power they put out about six volts, regardless of what (if any) brakes are attached so that's easy to check with a voltmeter by moving the manual override lever on the controller.... unless the controller is smart enough to check for the load of a brake system and turns itself off if no current flows. In that case, it would be necessary to hook up a big resistor to simulate the trailer's brake system, and again check voltage. Typical brake magnets have about 4 ohms resistance, so a single-axle trailer is about a 2-ohm resistance... but if you hook up a 2-ohm resistor and apply full 12V braking power, that's 6 amps of current and 72 watts of power, so you would need a high-power-capacity resistor to withstand the test. You could try a headlight bulb (one is 45 to 65 watts, or 4 to 5 amps at 12 volts, which is probably close enough), but shield your eyes from the bright light! A battery load tester might work, too.

Frankly, I haven't tried any of these schemes myself, because I had the trailer to use for testing.