Overview
The 5 pulses fault on a Worcester Bosch Greenstar Ri means the boiler’s service mode switch is not set to the MAX position. The boiler is telling you it is in the wrong service setting (often used by engineers for commissioning or servicing) and will not run normally until the switch is returned to the correct position. This is generally not a dangerous fault — it’s a configuration/status message — but it will prevent normal operation or limit the boiler’s behaviour while the condition persists. Why it occurs: the service mode switch can be moved during servicing, commissioning or accidentally when accessing controls. It can also show after certain board resets or if the boiler has entered a service range intentionally. Severity and who should act: this is typically low severity and can often be resolved by a homeowner with simple checks (confirming the switch position and performing a reset). If the message remains after checking the switch and doing basic resets, or if other fault lights or symptoms appear (no heating, repeated lockouts, low pressure), you should contact a Gas Safe registered engineer or Worcester Bosch support rather than attempting internal repairs yourself.
Possible Cause: Service mode switch not in max position.
Troubleshooting Steps
Safety precautions:
- Do not open or work inside the boiler if you are not qualified. Internal parts involve gas, live electrical connections and components that can cause injury or a leak.
- If you smell gas, leave the property immediately and call the gas emergency service. Do not operate electrical switches or the boiler.
- Isolate power to the boiler only if instructed and only if you are comfortable doing so; otherwise leave power on for diagnostic information and call an engineer.
Initial checks a homeowner can safely do:
1. Look at the boiler display and confirm it is showing the 5 pulses (or flashing blue light pattern) and no other fault codes are present.
2. Check the user manual quick-info or front-panel controls for any obvious service-mode indicator. Some controls will display text or an icon telling you it is in service mode.
3. Check the visible water pressure on the pressure gauge. If pressure is very low (below about 0.8–1.0 bar), top up the system following the manual before further troubleshooting. Low pressure can cause unrelated faults.
Specific diagnostic and fix steps:
1. Locate the service mode switch: consult your boiler user manual for exact location. On Greenstar Ri models this is usually a small switch or setting labeled MIN and MAX or a service function accessed behind the front cover or via the control dial/menus. If the switch is behind a removable cover and you are not comfortable removing it, stop and call an engineer.
2. If you can safely access the control, move the service mode switch to the MAX position as indicated by the boiler guidance. Ensure it is fully in the MAX position (not in-between).
3. After changing the switch, perform a boiler reset: either press and hold the reset or tick/OK button for several seconds (commonly about 8 seconds) or follow the reset procedure in your manual. Some models use turning the temperature dial to a reset mark and holding for 3 seconds—use the method for your exact model.
4. Wait up to 15 minutes. The boiler may run a short purge or low-burn cycle for up to about 15 minutes while it returns to normal. If the message persists beyond 15–30 minutes, proceed to the next step.
5. Note any other symptoms: no flame, repeated lockouts, persistent other fault codes, strange noises, leaks, or the boiler refusing to fire. Record any additional fault codes or LED patterns exactly as shown — this helps an engineer diagnose the cause.
When to call a professional:
- If you cannot locate or safely change the service mode switch position.
- If the 5-pulse message remains after setting the switch to MAX and performing a reset and waiting 15–30 minutes.
- If other fault codes appear, if the boiler will not fire, if there is a gas smell, or if you see water leaks or obvious damage.
- If the boiler is under warranty, contact Worcester Bosch support or your installer; otherwise book a visit from a Gas Safe registered heating engineer. Only a qualified engineer should open the boiler, check internal switches, wiring, sensors or replace components.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Worcester Bosch Greenstar Ri Boiler.