Potterton Suprima Orange Light Flashing

My sister asked me to look at her boiler, a Potterton Suprima, because it had been clicking on and off frequently and failed to heat the house properly on one day.

The boiler is the earlier Potterton Suprima but had the PCB upgrade kit 5111603 which replaces part number 407750 the troublesome PCB found on most Potterton Suprimas. The original PCB had two LEDs (red and green) which could be used to diagnose faults. The new PCB has a single LED which is able to produce three colours (Green, orange and red) and will flash various colours at various rates depending upon the boilers status.

The boiler was set to be on when I arrived, and had been on as the radiators were warm. When I looked at the boiler the orange light was coming on, there would be a click, the light would go out and kept cycling in this fashion at a slow pace. I checked the voltage at live and switched live which were both at 240v and steady. Looking at the fault finding guide which comes with the PCB upgrade kit, a flashing orange light on the PCB indicates that there is a problem with the temperature control and suggests to check the temperature control on the boiler is switched up which it was.

I checked the resistance of the thermistor on the yellow wires and it was within the range of 20k ohms to 4M ohms after unplugging it from the PCB. Testing it at the connector to the PCB tests the resistance of both the component and the cable at the same time. I wanted to check the resistance of the yellow wires as when the PCB was upgraded the engineer neglected to run the cables to the thermistor and overheat thermostat through the hole behind the fan housing which keeps them off any hot surfaces.

The flashing combined with the clicking from the PCB had led me to assume that the PCB was at fault rather than any other component, but wanted to check everything to be sure as they are not cheap. Replacing the PCB has solved the problem.

LED Indication Status	LED
Mains Off	Off
Mains On No Ext. Call for Heat	Continuous Orange
Ext. Call for Heat ( Temp. Control set to Off)	Flashing Orange
Air Proving & Ignition	Flashing Orange/Green
Burner On	Continuous Green
Boiler Temperature Control Satisfied	Flashing Green
LED Indicators Fault Modes Status	LED
Thermister Fault	Flashing Red every 5 sec
Wiring Harness Fault	Flashing Red/Orange 3 times/sec
Incoming Voltage <180V	Flashing Red/Orange once/sec
False Flame	Flashing Red/Orange every 5 sec
APS or Flow Switch Fault	Flashing Red 3 times/sec
PCB Fault	Continuous Red
Lockout	Flashing Red once/sec 5 flashes = Overheat 2 flashes = Ignition Failure
To establish cause press reset button for more
than 10 seconds. LED will flash Orange
once then Red, count number of Red flashes

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.