slcsubaru.com

From the manual
https://www.escortradar.com/pdf/8500manl.pdf

So press and hold both buttons for 2 seconds.

Press the left button and "Pilot" will appear, then the right button until it displays "V".

Leave it alone for 8 seconds and the detector beeps 4 times.

When it is just riding along it will display the current voltage, something like "14.3 V"

Below 10.5 volts it will display "LOW VOLTAGE" and gives an alarm
Above 16.5 volts it will display "HIGH VOLTAGE" and gives an alarm

Menu layout:

Wow, That is kinda cool!

So many people get in my car and say "What is that" I say the car voltage, they say "I have an Escort mine won't do that or I didn't know it would do that..

So there you go..