Ravenheat F73 Fault Code: Causes, Fixes & Repair Costs
What does the Ravenheat F73 fault code mean?
The F73 code appears on Ravenheat boilers when the control board detects a problem with the heating circuit pressure sensor. Either the system pressure has genuinely dropped to an unsafe level (typically below 0.6 bar), or the sensor itself has developed a fault and is feeding the PCB misleading readings — causing the boiler to believe there is a pressure problem when there may not be one. In both scenarios the boiler enters a lockout state, cutting off both heating and hot water until the fault is resolved. The closely related F74 code shares the same pressure sensor circuit and is often seen alongside F73 on the same models; if you see F74, the diagnostic approach is identical. Code 08 can also appear in conjunction with these codes when low pressure is the root cause.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Genuinely low system pressure Common
The most common trigger. Ravenheat boilers require system pressure of around 1–1.5 bar to operate correctly and will lock out when pressure falls below roughly 0.6 bar. Pressure can drop gradually through micro-leaks in radiator valves, pipe joints, or the boiler itself, or more suddenly if a component has failed. Check the pressure gauge on the front of the boiler — if the needle is in the red or below 1 bar, low pressure is almost certainly the cause.
- Faulty or failing pressure sensor Sometimes
If the pressure gauge reads a normal level (1–1.5 bar) yet the F73 fault persists after a reset, the pressure sensor itself is likely defective. The sensor may be sending an out-of-range voltage signal to the PCB even though actual system pressure is fine. A Gas Safe engineer can confirm this quickly with a multimeter test across the sensor terminals and its wiring loom.
- Wiring fault or poor connection to the sensor Sometimes
Corrosion, vibration, or a loose connector at the sensor plug can interrupt the signal between the pressure sensor and the PCB, causing the board to log the same fault as a failed sensor. Engineers will inspect the wiring loom and connector during any sensor investigation.
- PCB fault misreading sensor input Rare
In rare cases the PCB itself is unable to correctly interpret a perfectly healthy sensor signal. This is usually only suspected after the pressure sensor and wiring have been confirmed to be in good order.
How to fix it
- Check the pressure gauge and top up via the filling loop if pressure is low DIY safe
Find the pressure gauge on the front of the boiler. If it reads below 1 bar, locate the filling loop (usually a braided silver or grey flexible hose beneath the boiler with one or two valves). Open the valve(s) slowly until the gauge reaches around 1.5 bar, then close them fully. Do not overfill — 1.5 bar is the ideal target. If you are unsure where the filling loop is, consult the boiler's user guide or look for a label near the boiler.
- Reset the boiler DIY safe
Once pressure is restored to a normal level, press and hold the reset button (usually marked with a flame or restart symbol) for around 3 seconds. Allow the boiler a minute to restart. If it fires up and runs normally, monitor the pressure gauge over the next few days to check it holds steady.
- If pressure drops again, look for visible leaks — but do not re-pressurise DIY safe
Check around radiators, towel rails, visible pipework, and beneath the boiler for damp patches, drips, or corrosion staining. If you spot an active leak or the pressure falls repeatedly within a short period, do not top up the pressure again. Instead, turn off the cold water supply to the boiler and contact a Gas Safe engineer. Repeatedly topping up while a leak is present can mask the problem and cause further damage.
- If pressure is normal but F73 persists after reset, stop attempting DIY fixes Gas Safe engineer
When the system pressure gauge shows a healthy reading yet the fault code returns after one or two resets, the pressure sensor, its wiring, or the PCB is almost certainly at fault. Further DIY attempts will not resolve this — a Gas Safe engineer needs to test the sensor output with a multimeter and inspect the wiring connections before deciding whether to replace the sensor or investigate the PCB.
- Call a Gas Safe registered engineer to test and replace the pressure sensor or carry out further diagnosis Gas Safe engineer
A qualified engineer will test the pressure sensor electrically, check the wiring loom for damage or corrosion, and verify the PCB is responding correctly. If the sensor is confirmed faulty it will be replaced — a relatively modest repair. Be aware that Ravenheat Manufacturing ceased trading in 2025, meaning spare parts are becoming increasingly difficult to source. Your engineer may need to source parts through specialist suppliers, and lead times may be longer than usual. If a major component such as the PCB is also implicated, discuss with your engineer whether the cost of repair on an ageing Ravenheat boiler is worthwhile compared with fitting a replacement boiler from a manufacturer that still has full parts availability.
Parts you may need
- Heating circuit pressure sensor · from £22
- Pressure sensor wiring loom / connector · from £18
- PCB (printed circuit board) · from £280
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £100–£280, depending on the underlying cause.
Frequently asked questions
Can I fix the Ravenheat F73 myself?
The only DIY steps that are safe and useful are checking the pressure gauge and topping up via the filling loop if the pressure is low, then attempting a reset. If those steps clear the fault and pressure holds steady, the job is done. Anything beyond that — testing or replacing the pressure sensor, inspecting wiring, or touching the PCB — must be carried out by a Gas Safe registered engineer.
What is the difference between the F73 and F74 fault codes on a Ravenheat boiler?
Both codes relate to the heating circuit pressure sensor and are often seen on the same models (CSI and RSF). F73 typically signals a sensor fault or a signal outside the expected range, while F74 is sometimes associated with the sensor reading being stuck or implausibly low. In practice the diagnostic steps and likely repairs are the same for both codes, so treat them as closely linked faults requiring the same investigation.
Ravenheat has stopped trading — can I still get parts?
Ravenheat Manufacturing Limited was dissolved in 2025. Spare parts are still available from some independent heating parts suppliers and online marketplaces, but stock is dwindling and prices for items like PCBs are rising. If your boiler needs only a pressure sensor, parts are still fairly accessible at the moment. For more expensive or complex components, the cost of repair may approach or exceed the cost of a new boiler from a current manufacturer — it is worth getting an honest assessment from your engineer before committing to a major repair.
How much does it cost to fix a Ravenheat F73 fault?
If the fix is simply topping up system pressure and the pressure holds, there is no repair cost. A professional pressure sensor replacement typically costs around £100–£280 including labour. If the PCB turns out to be the root cause, that can add significantly more to the bill — PCBs for Ravenheat models currently cost in the region of £250–£400 for the part alone, and sourcing them is becoming harder. For boilers over ten years old, many engineers will recommend weighing up the cost of repair against a new boiler installation.