Just bought a new car and had a hitch installed at the dealer - they claim that the wiring harness was properly hooked up, too. Problem is that the boat trailer lights don't work at all -

Took back to dealer and they swear that the trailer light connection (on the car) has power, etc. They say the trailer lights must have all burned out which I find to be unusual at the least.

Can I go to an auto parts store and get some type of light meter to see if there is indeed power to the car light connection - like when the headlights are turned on? What kind of device should I buy?

Should I take the car (with the boat trailer attached) to a boat repair shop - or to my car dealer to have fixed?