2006 t600 a couple problems I need some help on

I bought a 2006 t600 with 600k on it a month ago..truck started out as a good truck then for the last couple weeks I've started having a couple unrelated problems . The first problem I noticied the lighter jacks stopped working and fuse is good then all the dome lights quit working and while all this started happening I noticied the voltage gauge would read 14volts then a half later I'd look down and it would be at 9 or 10 so I stopped at a ta stop and they talked me into buying a alternator which did nothing different so they checked that alternator was putting out 14volts and also at the starter which it was but said I needed 3batterys which still test good with a load tester so I'm lost .also I noticed a buzzer alarm sound the day the dome lights went bad which I'm assuming is the low voltage buzzer?? Could the low voltage module cause all of these problems?? The other problem is I'm noticing antifreeze forcing itself out of the overflow tank so I replaced radiator cap and still didn't fix it sorry for any typos I'm typing this from my phone otr

 

Ok I'll look for it but didn't see it in there also the radiator cap fits but not as tight as one would think I can still move it a little but the kenworth dealer said this is the one so idk

 

found it thanks