Voltage at the HCV will only ever be vehicle voltage, 12 or so, or 0v.
Temperature is regulated using pulse modulation, ie. solid 12v for cold, long pulses of 12v with bits of 0v for cool, shorter pulses of 12v for hotter and constant 0v for full hot.
So you need to wait to see what you have, not just a case of a measurement straight away.
That said, you should have constant 12v for cold and constant 0v for hot on demand.
If that is not the case then suspect the panel. In the first instance sweep the heat dial back and forwards a few times to clean the potentiometer, if you still have voltage other than the above then its time to replace.
Incidentally analogue meter is far better for this job as you can see the pulse width more easily. As is the driver's side indicator repeater in the wing as that's the same plug and will give you a nice bright visual indication of what is going.