68 Barracuda........ Temp and Gas Gauge Issue.

If your meter was reading just mV (millivolts) at the end of the temp sender or fuel sender wire, then the IVR is kaput or your connections are bad somewhere. Testing at the end of the tmep sensor wire is the quick way to check; your meter should be pulsing from 0 to some voltage up to 12 volts about once per second (but this will vary a lot from meter to meter).

If the 'this' circuit' that you are referring to is from the gas gauge to the temp gauge on the circuit board, then yes, you should see the pulsing voltage there.