Carver Cascade 2 water heater

Camper van, camper, caravan, motor home , RV water heater repair or fix.
My heater wasn't working properly seems I got , may be it turned on 3 times max , the other attempts failed . Because of that I got a new unit over the eBay, the seller claimed its new but i don't think so. I could see some discoloration from heat on the gas burner. May be it was just tested, may be I'm wrong. It was never unsealed before me, i pulled the seal. I am planning to fix the old unit anyway. Its not working anymore and I think its because of the remote being "fixed" to last. I have a new PCB board for both : the main unit and the remote. Waiting for some parts from china. Mouser website have good quality electronic parts but really expensive and the most expensive is the postage . It is not worth to buy unless you making a lot .
The bad think about these things is the fact that no electronic schematic diagram can be found on the internet. Which make the trouble shouting way easier. I had to figure out how the unit actually work. Takes time, well for me anyway.