does anyone have an AHP 300 service manual

The 3 and 6 years maintenance are “factory” overhaul level maintenance much like your 60,000 or 120,000 miles car overhaul. Allied will not give those out as they are their money maker for service revenue. They will claim that they have provided maintenance (verification procedures) for the other years (1,2,4, and 5). I have run across this type of situations many times. Try go to your sales rep and see if s/he can cut one loose or know of someone at the factory. If that failed, then you would have no choice to send it to the factory. Tell your sales rep that you will recommend to your administration to not buy from Allied Healthcare in the future. That might work. Good Luck.