apu wont start.

I have a proheat apu. It currently wont start. It was starting but would die after 5 minutes or less. I brought to a local shop who said it keep tripping a relay, then they tried to replace it but that relay tripped, so they said its a bad board. I got fed up and took the truck back, now the apu wont start at all since they had it. (outside temp is colder too). I just bought the truck so i do not know the apus prior history. Any troubleshooting suggestions?

 

Why is it not a apu? It most derinately is.... i did not say bunkheater

 

Bad capacitor to genenator. glowplugs board and relays work great.

 

Also fuel was not primed to bleeder screw