While in the shower this morning the flow of water suddenly stopped completely. No hot or cold water flow at all. I still have normal water pressure and available water flow to bathroom sinks and the rest of the house. Checked for leaks under the house, none. What would cause my Shower faucet 1324 to suddenly stop? Turning the valve left and right there is no available flow.

your not making sense with you question --state it goes cold in middle of shower --but state it will stay hot or cold forever ----if its the latter continued hot till you shut off water that normal working if the unit shuts down during shower then you have a problem ----unit is set at one temp and runs at that temp and you use shower 1 handle / 2 valve what ever you own to adjust temp their are really only 4 reasons stops making hot water ----2 are usually well water supply --incoming water pressure /flow or to cold ----other are gas valve -or sensor so i would look into your shower handles since almost all have adjustments and anti scold safety

Lots of shower valves have pressure balancing cartridges nowadays in order to get full flow out of hot or cold you have to have both the hot and cold hooked up to give even pressure on both sides of the cartridge that should fix your problem and give you a full flow

when he soldered the connections on these pipes.. he may have partially blocked the flow with solder inside..if its restricted up to 50% then its a hell of a pressure loss..hot water is always lower in pressure anyway..also take the shower head and dunk in a clr solution it may have calcium deposits inside the small plastic orafices in it..

Its a tankless heater. It will heat water as long as it senses a large enough flow of water. Either the flow sensor is bad, or not sensitive enough, or you are using less water than it is set to work at. Try keeping a large flow running. Instead of a trickle, shut it off entirely.

Could be the pressure on the hot water flow is insufficient, you really need a 5/6 feet head of water from the shower head to the bottom of the storage tank for sufficient pressure.

I had the EXACT same problem (installed my tankless last winter and worked fine, now this summer it fluctuates, have to turn the shower completely off and then on again to get any hot water and then it only lasts for a couple of minutes!) Argh - it is frustrating!

Here's what I found: the demand for hot water is lower during the summer (hot) months because the "cold" water coming in is already quite warm. You don't need as much hot water to make the shower temp comfortable. SO, my tankless was shutting off due to low flow demand. I've removed the flow restrictor from my shower head and it helped alot but didn't completely solve the prob. Next step is what has been recommended to me by several people but is much more expensive - change the pressure valve on your shower to a temperature valve. Or just wait til winter and it should work ok again :)

The way anti-scald valves work is there is a slide tube inside the faucet which requires pressure from both hot and cold or else it will cut off the flow. As for temperature adjust I do not believe there is an adjustment screw but more so there are these white plastic toothed stop rings which prevent the handle from turning 360 degrees. When your adjust the stop ring, it adjusts how much hot water is allowed to mix with the cold water. My wife likes her showers a lot hotter than I, so I gave a good allowance with the stop ring. The "adjustment screws" which you are viewing are not for adjustment of temperature, they are remote cut-off screws to stop the water entirely to change the washers in the unit if needed. SO open those all the way and leave them open. Think of them as not having to go all the way into the basement to shut off the water supply just to change a few washers.

Does it happen to any other fixture? If not, it's most likely your shower valve and not heater.

sounds like you may have a little debri on hot side stem or kinked hose between valve and spout turn off water to house remove handle pull bonnet and remove stem turn water back on with stem removed see how water flow is be careful turning water on you could make a mess i am assuming the low pressure is in shower only

you need to change the cartridge