Installed the converter in my travel trailer. Input connected to tow vehicle 7-pin connector and my dvm reading on the input to the converter i 14.2 volts with the vehicle running. Want to adjust the output voltage to 14.4 for my Lithium house batteries. When I connect my Digital voltmeter to the output, however, the reading jumps all around. No steady output voltage reading. No load on the converter, no battery connected to output. Is the unit defective or am I doing something wrong? Thanks for your help!