As our shower is running and the water pressure goes from high cut out to low cut on the water temp changes. With the higher pressure the temp is hotter and gets cooler as the pressure drops. There seems to be about a 10-15 degree change from high to low pressures. My tank switch is set from 35-65 psi and is working correctly. Any idea where this change is coming from? My hot water heater is new and the bladder pressure in my tank is set about 5 psi below the start pressure on the switch. Thanks for any ideas.

Do you have a pressure balancing valve in the shower faucet? What brand of faucet do you have?

I don't know. I have not been able to get any info on the valve. It is an American Standard that I think is about 10-12 years old. Attached is a picture of it. I cannot figure how to get it apart if it does have a cartridge. Ideas? Thanks, Robin.5826

I don't know. I have not been able to get any info on the valve. It is an American Standard that I think is about 10-12 years old. Attached is a picture of it. I cannot figure how to get it apart if it does have a cartridge. Ideas? Thanks, Robin.5826

There should be a small indent somewhere on the backside of the 'crystal' of the handle.

If it's as old as you say, thoroughly drench the handle and 'crystal' with vinegar and let sit for a good forty five minutes or so before attempting to slide a small bladed screwdriver or automotive pick behind the indent to pry the 'crystal' out.

Is this a new problem since you got a new water heater?