Shower hot water goes to trickle

[beuermant]

Specs:
Price Pfister single knob shower control, no tub.
Price Pfister Avante cartridge (S74-292)

Symptoms:
With knob on cold, full (and good) pressure. As knob is turned towards hot, the pressure maintains and the water gets warmer, until a certain point, when the pressure slowly goes to a trickle. The trickle is hot water. Turn back to cold and pressure picks up back to full. Hot water comes out at full pressure everywhere else in the house including the faucet in this bathroom.

Troubleshooting:
I have taken the cartridge out, ensured no blockages in it or the valve assembly. Same results. Replaced the cartridge with a new one. Same results. Took cartridge out and turned water on to try and break anything loose that may be in the hot water line. Nothing changed. At the point the water pressure goes down to a trickle, the valve is almost blocking the cold water inlet completely.

I don't know what else to do other than cut pipes and replace the entire valve assembly, hoping that that fixes it, but it doesn't seem that there is anything wrong with the current one. I'd rather not have to do this anyway.

Any other suggestions? Thanks.

 

[Matt30]

Some of those price pfister valves have almost like a balancing spool mechanism behind the cartridge. If yours has one, try taking it out, soaking it in some CLR and see how that helps. Or contact price pfister for new guts of your shower valve

 

[journeyman]

Do you loose pressure on hot side throughout house

 

[beuermant]

I've replaced the internals of the valve with the same effects.

Nope, no lose in hot water pressure anywhere else in the house.

 

[journeyman]

How old is heater

 

[journeyman]

What kind of valve is it

 

[beuermant]

Type of valve in specs above.

Water heater is 7ish years old

 

[journeyman]

Try turning on two hot fixtures and see what happens to them both