troubleshooting turn coordinator

I have a brand new turn coordinator on my panel that just quit working. Less than 25 hours. The supplier told me they would replace it, but to make sure it was getting power before sending it back. I didn't wire my own panel and don't know all that I should about electrical stuff, so please be kind with your answers.

Here's what I did. I used a voltmeter. The turn coordinator connection has two pins housed in a small coupling that is secured to the back of the instrument. First I got a 12V reading by checking the power and ground wires just behind the coupling. 2nd, I touched the voltmeter leads to the pins housed in the coupling. no reading. reversed the leads, no reading. then I touched the pos. lead to the positive pin and the neg lead to the airframe and i get a 12v reading. Shouldn't this mean that the ground wire connection at the coupling could be bad. and not the instrument? Before I try to take the coupling apart and rewire it, i wanted to double check. thanks

You've got 12v where you should. Sounds like the instrument is bad.
Steve

Jack,
If you don't get 12v between the pins, it sounds like the ground pin is indeed open. The instrument doesn't provide a good ground through the case. Sounds like you need to resolder the ground pin connection.
Mel...DAR