I have a guy that I call that is an expert on ProHeats. His name is Jim and is out of Rockford, MI. His shop is called J&K Diesel. I call him frequently with my APU issues and he guides me through how to diagnose my problem(s). A couple of times I have had him overnight parts to to a truck stop that I know I can be at the next day. I send him $50 every now and again to cover the time he spends with me on the phone. I have never met him face to face.
His number is 616.813.3091