Tepid Water - Control Board Code "ur"

[imnotaplumber]

Hi Guys,

My PulsaCoil A class is now only producing mildly warm water for a few seconds then cold.

It has the following code displayed on the Control board.

"ur"

Note: The left period is flashing but indicating "Normal Operation" but could not capture it in photo.

Referencing the Gledhill manual this seems to indicate "S5 Sensor (bottom) calling"

I have checked the header tank, power cycled the appliance (switch off on the appliance as well as the two main power switches on the wall), which unfortunately has not helped.

Anything I can do personally to try and kick it back into life/diagnose further/clear the codes? Or does this sound like a job for the pro's?

Cheers
Simon