Fresh Water Pump Start Up

[Swagman]

Hi Guys. Couldn’t work out how to delete this from General Repair thread so repeating it here.
We’ve a 16 yo International and can’t resolve what seems to be a small problem. Hoping someone can help.
Our 12v water supply switch has 3 choices. Internal, External, and Fill.
The pumps work fine on External and Fill, but not when switched to Internal.
The two pump fuses I can find (on the power supply / charger) , appear ok.
Is there another fuse somewhere that I’m missing?
Could the switch itself be faulty?
Is it common for a pressure cut out in the pump itself to fail - perhaps stuck in the ‘pressurized’ mode?
Any guidance on where’s best to start sorting this would be much appreciated. Thanks in anticipation….

[STREMN]

Hi - I removed the other thread so you won't have duplication.

I'm no help with your problem...our water pump is strictly for using the internal fresh water supply. External or "City" water supply is pressurized from the incoming water source at the "City Water" inlet. To fill the internal fresh water we manually open the "Fresh Water Fill" door and put a water supply hose in it. So we've got separate "Water Fill" sources, where yours sounds as if it runs off one for the same chores.