Built my house in 2005. We have a tankless hot water heater. It appears to be working fine. Plenty of hot water from other faucets.
Guest bathroom shower is all from original contractor install. Single-lever ball handle, American Standard - lift to start water flow, turn handle to adjust temperature.
About three weeks ago, I noticed that the water in the shower is either totally cold or too hot. I can't get a "warm" temperature. If it's too hot, for example, and I "nudge" the lever to the right, the water becomes completely cold. And vice versa.
The water pressure, regardless of temperature, seems fine. I do not notice a drop in pressure whether the temp is all cold or all hot.
So, before I call a plumber, I am wondering if this is possibly the sign of a bad cartridge, which I think I can replace on my own and skip the repair bill. However, I really don't want to waste my time disassembling the faucet if a bad cartridge could not be causing this problem.
Would appreciate your thoughts. Thank you!