Shower won't stay hot

[AKSilvers]

Helping my elderly dad with his shower. Water would get cold then scalding hot. When I went to shut off valves behind wall found cold water valve throttled almost shut. When opened fully checked water in shower and it got hot then cooled off within 5 seconds. When turned to hottest position it got hot then again cooled down. Water doesn't cool down to temp of water entering the home, but too cool to shower. I replaced cartridge, but same results. All other faucets work fine. The shower is a single handle type. The shutoff valves in wall have a threaded screw going into body, not sure what this is for.

 

[Jeff Handy]

You need to show pics of everything.

The shower valve, handle, and trim.

Then pics showing the whole valve behind the trim.

It might just be an old style valve that will never get better.

Or it might be an anti scald pressure balancing valve that needs more servicing.

 

[AKSilvers]

pics in order of disassembly

 

[SHEPLMBR]

What is up with all of the electrical? This is not your standard set up. Might want to call Kohler and see if they could help trouble shoot.

 

[Jeff Handy]

That wiring with loose goofy receptacles looks like cousin Moe or uncle Joe did it, while hooking up the spa pump.
Not safe around water, even if one or both are gfci, if it is even wired right and grounded.

 

[SHEPLMBR]

That wiring with loose goofy receptacles looks like cousin Moe or uncle Joe did it, while hooking up the spa pump.
Not safe around water, even if one or both are gfci, if it is even wired right and grounded.

yeah you are right I think. I just saw the name and went right to some over-engineered stuff.

 

[Jeff Handy]

You might have changed the mixing cartridge, but did not change the pressure balancing unit which is behind it?