Originally Posted by RogerR
Sounds like the thermostat that regulates the heating coil is toast. Try a search online for the temperature regulator or thermostat for that specific model number. It may be a simple fix. Water pressure has no effect on the temperature, it should always shut off when it hits the set max.
Only took a second to find this youtube on it but you didn't mention the exact model so you may have to look further.
The OP has a Girard on-demand WH, not a Suburban.
Originally Posted by Evans
I have a 2017 Jayco Greyhawk with an on-demand water heater that provides dangerous hot water temperatures. I have it set to 104 and it’ll run up to 120F. It appeared to be intermittent so thinking it was varying water pressure at different parks, I put a pressure regulator on. Still intermittent. Any ideas?
Are those numbers from the inside thermostat display? If not, it could be your outlet temp probe.
If you truly believe it is a pressure issue, fill your tank and try it with the pump.