truck is a service vehicle that has had timely service its entire life

I would first try getting the battery tested.
This could be a problem with your alternator belt as well. You should inspect it. See if it is nice and tight.
Check your battery cable connections. They should be clean and tight.
I don't know how the alternator was checked but it should be "load tested". This is a specific test that is more reliable than simply checking to see what the voltage is when it is charging.

ok one more time the battery and alt cheked good what else could it be I wouldnt be here if it ha dtured out to be either and they were properly tested and the battery cables and connectors are in good shape so whats next on a priority list im not an expert but is there something after those have been found to be good.

OK. What is the battery voltage when the truck is not running? What is the voltage when it is running?
Let me know and I can help you more.

ok while the engine is running the voltage from the battery reads 12.42 with engine off it reads 12.06

OK. The first thing that needs to be addressed is that your battery needs to be charged. It should have a minimum of 12.65 volts with the engine off.
The second thing is that your alternator is not working at all. With the engine running it should read a minimum of 13.5 volts or so. This may be because the alternator is bad, or it might be because the belt is slipping or it might indicate that there is a wiring problem in your charging circuit.