Lost hot water to shower

[Edneedshelp]

I have a single knob tub/shower faucet that has worked for the past 20+ years. It has not been used since this past winter. When my wife tried to soak in the tub there was no hot water. I changed the Delta 1600 series cartridge but that did nothing. I had my wife in the basement turn on the water after I removed the cartridge. Water only came out the right side of the valve (if that is the proper name of the unit that the cartridge fits in)
The pipes are copper and the house is about 22 years old.
What do I do next . Everywhere else in the house has hot water?

 

[Jadnashua]

Some valves have a separate pressure-balance spool valve. It adjusts the hot/cold mixture when the pressure changes (say when someone flushes a toilet) so that you don't get scalded. Yours may have a separate one of those. IT can get jammed to one end when you shut off the water supply. It normally prevents any water from flowing. It may need to be disassembled and lubricated, or replaced, assuming that's the issue...but, read on.

The other, potentially more likely situation is that you need to adjust the hot limiter of the valve...IOW, you can't turn it far enough to mix in enough hot to make it your desired temperature. Look in the tutorial section - I put a thread in there that describes the problem, and has links to adjustment procedures for at least some of the different brands. The instructions for the cartridge may also show how to do it on yours. This is either a screw, cam, or tab that must be adjusted to allow it to mix in more hot.