1.the water pump should not run when filling your fresh water tank. I can’t believe a Rv tech would say that.
2. Is the winterizing value open, it will suck air continuously into your system and the pump will continuously run.
3. Maybe your fresh water/fill valve is broken.
4. Rarely, the connection for your fresh water is kinked and doesn’t allow water in.
Believe me I’ve seen that, usually on a brand new model. They cut the PVC too long, put on the connection and screwed it in kinking the PVC tubing going to the tank.
Let me know if this helps
I would check in that order.
The fresh water/fill valve is plastic and it can freeze if it wasn’t winterized properly.
A common mistake is not to stick you finger into the fresh water connection and release the one way valve pressure.
Some people forget and it freezes and cracks. That leaves a open air entry point that will keep the water pump running.
2020 Winnebago Horizon 42Q
Maxum Chassis, 450 ISL
99 Storm 30H, 04 Southwind 32 VS, 07 Ellipse 40FD