Fault finding
23 real call-outs, in the customer’s words
In short
These are the heating-controls faults an engineer really gets called to, weighted by how often each one happens. Every page gives the symptom as the customer describes it, the method, what the meter shows at each step, and the answer. In the simulator, each one is a live circuit you can meter.
If this is your home: this page is written for heating engineers. Mains wiring and gas appliances are not DIY jobs; call a Gas Safe registered engineer. If you smell gas, leave the building and call the National Gas Emergency Service on 0800 111 999.
No heating
The customer says“Hot water's fine but the radiators are stone cold, whatever I do with the thermostat.”
- Heating zone valve: motor failed
“It used to whirr in the airing cupboard when the heating came on - now it's silent.”
S-Plan · Obvious once you look
- Heating zone valve: end switch failed
“I can hear the valve open, but the boiler never comes on for the heating.”
S-Plan · Needs a proper trace
S-Plan · Needs a proper trace
- Room thermostat not switching
“I've turned the stat right up and nothing happens.”
S-Plan · Obvious once you look
- Programmer: heating channel failed
“The programmer says heating ON, light's on and everything.”
S-Plan · Needs a proper trace
Y-Plan · Obvious once you look
Y-Plan · Needs a proper trace
- Wireless receiver relay failed
“The thermostat shows the flame and the receiver light's on.”
Combi · Obvious once you look
Combi · Obvious once you look
No hot water
The customer says“Heating's lovely and warm but there's no hot water - the cylinder's cold.”
S-Plan · Obvious once you look
S-Plan · Needs a proper trace
- Hot water valve brown landed on the wrong terminal
“Hot water hasn't worked since another firm was in last week.”
S-Plan · Needs a proper trace
S-Plan · Obvious once you look
- Cylinder stat wired to its SATISFIED terminal
“Funny thing - the hot water only seems to heat when the tank's already hot.”
S-Plan · Subtle or misleading
S-Plan · Needs a proper trace
Nothing works
The customer says“Nothing works. No heating, no hot water, and the controls are dead.”
- Blown 3 A fuse in the fused spur
“The little red light on the switch by the boiler is still on, mind.”
S-Plan · Obvious once you look
S-Plan · Obvious once you look
Boiler will not fire
The customer says“The programmer's on and I can hear things whirring, but the boiler never fires - no heating and no hot water.”
- Boiler switched live open circuit
“Valves are opening, I can hear them, but the boiler just sits there.”
S-Plan · Needs a proper trace
- Boiler live and neutral reversed
“New boiler was fitted Tuesday and it's never worked.”
S-Plan · Subtle or misleading
Boiler never switches off
The customer says“The boiler never switches off. Everything's OFF at the programmer and it's still running - the bills are frightening.”
S-Plan · Subtle or misleading
Pump not running
The customer says“The boiler fires, makes a terrible kettling noise, then cuts out. The radiators hardly get warm.”
- Circulating pump seized
“Boiler fires up, bangs and kettles, then cuts out. Rads are barely warm.”
S-Plan · Needs a proper trace
Hot water only with the heating
The customer says“We only get hot water when the heating is on as well.”
- Y-Plan: cylinder stat call wire open circuit
“We only get hot water when the heating's on. No good in summer!”
Y-Plan · Needs a proper trace
Intermittent fault
The customer says“It keeps cutting in and out. Works for a bit, the boiler drops off, then it comes back on its own.”
S-Plan · Subtle or misleading
The 5 diagnosis challenges
Timed, on a working S-Plan, with a hidden fault and four hints that never name the part. They make up the Fault Diagnosis course.
No Power to System
Easy · 5 minCall-out: 'Nothing works - no heating, no hot water, and the programmer display is blank.' The fused spur is on and its neon is lit.
Heating Not Working
Medium · 10 minCall-out: 'Hot water is fine but the radiators never get warm. The programmer says heating is ON and I have turned the room stat right up.'
Hot Water Not Working
Medium · 10 minCall-out: 'The heating works but we have had no hot water since another firm fitted a new zone valve last week.'
Valve Stuck
Hard · 15 minCall-out: 'Heating is not working. I can hear nothing from the airing cupboard when it comes on - it used to whirr.'
Intermittent Fault
Expert · 20 minCall-out: 'The boiler keeps cutting out and coming back on by itself, every few seconds, even though the heating is calling all the time.'
Your first fault is waiting.
Three of these call-outs are in the free demo.