How to Test 12 Volt Trailer Accessory Circuit to See if its Carrying Voltage to Trailer Battery

Updated 07/25/2018 | Published 07/24/2018

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Question:

I have a lance 825 - the previous owner cut off the 6 pin from lance and wired a 7 pin. all of the truck camper lights work, but the batteries wont change. I know the 12v on my truck plug is hot - but am unsure how to test the truck camper plug side. I am able to charge the batteries on shore power - so that leads me to believe its strictly an issue with the truck camper plug?

asked by: Dave

Expert Reply:

Easiest way would be to use a circuit tester like the part # PTW2993 which comes with a needle and hook setup to allow you to probe a wire to test it. Use a tester like this to probe the circuit for the 12 volt accessory circuit that should be charging the battery to know if the circuit is carrying voltage. You should note that this circuit does not carry enough amperage to really put a decent charge on a battery. It can hep keep a charged battery topped off but it won't charge a depleted battery.

You can also look for corrosion or ben pins on the trailer connector to see if that's why the circuit might not be functioning.

expert reply by: Jameson C