It doesn't say the IVR puts out an average of 5 Volts. It says the effect is the same as steady 5 Volts. Good info for testing the gage but not directly useful for verifying the IVR. When I tested the IVR in the '67 rally cluster you can see the voltmeter needle swings practicaly to full scale (8 Volts). Its not a true square wave or perfectly consistant in frequency. (link to video below) https://www.forabodiesonly.com/mopa...ltage-5v-or-6v-nominal.514919/post-1973864067Scroll through that thread ^^^^^^
You'll see several ways the gage and sending units can be checked.
Begin with a simple check of resistance in the gage and the sending units
Then you can input a 3 to 6 votls of dry cell power
and/or hook up some resistors or a potentiameter to simulate the range of resistances for the sender and input battery power through the IVR.
pdf version of the Master Tech Conference posted at MyMopar.com