Re: Water Temperature
How old is the shower faucet itself? Do you have a whole house filter after the well pump?
The reason I ask is due to calcium build up inside the shower cartridge. If you have another show does this also happen there?
Also, there should be an expansion tank just after the well pump. This creates the pressure build up for the house itself. If the bladder inside the expansion tank is bad (it should sound hollow)(if it is broke it will be full of water), replace it. There is also a pressure switch and a check valve off the pump. but, that is another story.
Process of elimination. Good luck.