i have 4 Aaon rooftops on top of a hotel in Naples. And two of witch have no charge i spent all day Friday looking for leaks. units are 2 year old i put 200psi of nitro and 1lb of 410 as a trace gas after spending 2 hrs looking for the leaks with my crap tech mate leak detector and my psi dropping 5psi. I went out and got a fieldpiece leak detector witch cost me $305 come back and find leaks in my reheat coil valve on both units. After calling around a rebuild kit is $407 my valve $420 i need 2 and 65lb of 410. so this week i strongly dislike Aaon.
Those step valves aren't real easy to braze in the way they're mounted at the side of the unit.