One shower loses heat, but every other shower/faucet ok

[MarlaK]

Hi. I have a tankless water heater in my home. We have no issues with hot water in any faucet except one. In our master bath, the shower constantly loses heat. If you turn it off for awhile, it’ll start running hot again, but then will run cold again after a few minutes. Any ideas what would cause this in just one faucet?

 

[Terry]

What brand and model of shower faucet is giving you problems?

 

[Sponsor]

 

[MarlaK]

It's an Aqua Star Model 240FX.

Link added by Terry

Replacing an Aquastar 240FX with Bosch Therm 830ES

The Aquastar model 240FX was a unit that was distributed by Controlled Energy Corporation (CEC) many years ago. The 240FX was manufactured...

bosch-therm-tankless-water-heaters.blogspot.com

 

[MarlaK]

Oh, sorry, you said faucet. It's a Santec faucet, but not sure what model. It's old.

 

[MarlaK]

I took a pic. Here you go.