Can the 12 Volt Circuit on Trailer Connector be Turned Off when Vehicle is Turned Off

Question:

is the smaller 40 amp post switched. On when ignition is on. Off when ignition is off. There by separating the rv battery from the starting battery? I have tried mine and it appears not switched. Do I need to install a solenoid to separate the 2?

asked by: Jim S

Expert Reply:

Once connected, the 12-volt circuit on the trailer connector on some vehicles could be hot all the time. You can check this by using a circuit tester, such as # PTW2993 if needed, to test the 12-volt pin on the vehicle side trailer connector. If it shows power with the vehicle off, then you know it is hot all the time.

Adding a switch is not necessary if you just disconnect the 2 when not towing. The other option, like you said, is to add a solenoid. In this case it would be a battery isolator, # PK5231201. I have included a picture showing how this solenoid wires in. When the vehicle is turned on, the solenoid will allow power to go back to the trailer connector. Turn the vehicle off and it does not allow power to go back. If you do need it to shut off with the vehicle not on then the solenoid is the way to go.

expert reply by: Michael H