RE: HWH customer service phone number is a joke
Get used to it. There is a labor shortage, maybe/partially from stimulus checks and covid fears. Ur lucky to get a warm body let-alone an experienced tech anymore. Labor is in control. Try to do as much as u can and you may surprise yourself on how much you can actually do. Happy trails.
RE: Onan QD 7500
Do you have two start switches? One on the generator and one inside the coach? If so, try the other switch to see if it starts? The fault codes may be in your owners manual?