I worked for an Ins. Co. inspecting manufactured homes for many years. The HVAC system is usually located in the hall near a bathroom. I would look closely for additional leakage from the plumbing system in the hall bathroom and washing machine plumbing. Crawl under the house and look at the bottom of the subfloor where the underbelly/insulation has probably fallen out due to the water damage. The bottom of the floor will usually give you a better idea of where the leak is and the condition of the subfloor.