Circuit board voltage limiter test

Greetings,

I am in the process of replacing the circuit board on my 76 dart.I wanted to test the voltage reducer and the multimeter kept flashing anywhere between 0 and 5 volts.So I grabbed a second one and the same thing happened.Should it read a steady 5 volts?Or is it o.k. to fluctuate as long as it doesn't go over 5 volts? I thank you in advance for your help.:-P