It has a post heat cycle for the first few minutes the engine is running. It warms the intake air to reduce white smoke from the engine when it is cold

 

Thanks! That makes a lot more sense as to why my volt gauge bounches back and forth as the pickup warms up. Is it normal for other gauges to fluxuate back and forth while this process is working? My newly installed Pyro gauge needle bounces up and down in conjuction to the voltmeter while this grid heater cycling is occuring.

 

It draws quite a bit of power so your voltmeter will drop a bit. It will be worse if your alternator or batteries are getting tired. The bouncing you are noticing in your pyro guage may be caused by it not getting enough power when the grid heater comes on.