Got a call from a customer, their SCM125zj outdoor with 5 x SRK 25 Zj indoors had stopped working, with indoor run light flashing continually, timer light flashing four times.
Discharge pipe thermistor faulty! I ordered new thermistor set, popped down, fitted, ran, tested, fine no apparent problems, cool suction and suction pressure about 110psi which seemed ok. All 5 units running and rooms down to temp.

Next working day, system ran for a period and stopped with same fault flash code.
Refrigerant charge seemed ok when I fitted thermistors, could a very slightly low gas charge give high discharge pipe temp causing the thermistor to go in to fault, Will the new thermistor be damaged and need replacing again? Any other ideas ???