Welcome to the forums!
I would call a local mobile RV technician, you can locate them via:
https://camperfaqs.com/mobile-rv-repair
https://rvtaa.org/locate/
https://nrvta.com/
https://nrvia.org/
https://nrvia.org/locate/
It appears they are more willing to work on these RVP units than camper repair shops, plus they seem to be more knowledgeable and truthful about their capabilities.
There are a handful of us members who have repaired their unit by themselves.
Be advised Coleman Mach/RVP no longer makes the 5 different units, they were all replaced by one model with conversion kits, the 6515 model. However, parts for our old models are still widely available.
You will find your model# on the left end of the cabinet at rear cap, might have to use a small mirror to view the data-sticker
When you know your model# you can download the free service manual from the internet, it includes an excellent trouble-shooting section.
EDITED to add this how-to for removing and repairing an RVP basement heat pump:
https://www.irv2.com/forums/download...do=file&id=435
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2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA.
"We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution." Abraham Lincoln