Worcester Bosch Boiler Locked Out, How We Helped (and How You Can Too)
Location: Wolverhampton – Greenstar Combi, Low Pressure Fault
We were called out to a customer in Wolverhampton who’d been left without heating or hot water, and wasn’t quite sure what was wrong. No leaks, no banging noises, just a flashing code on the boiler screen and a cold house.
The display was showing EA, and the pressure gauge was sitting well under 1 bar.
What was going on?
The boiler had locked itself out because the pressure in the system had dropped too low. It’s a built-in safety feature on Worcester Bosch combi boilers. If the system loses too much water (even a small amount), the pressure drops, and the boiler shuts down to prevent damage.
The customer had tried pressing reset, but the boiler wouldn’t fire back up. They weren’t sure what the code meant or what to check next.
What we did on this job, and what you can try too
We spotted the pressure issue straight away and talked the customer through topping it up safely. Below is a full guide showing the steps for the most common Worcester Bosch filling loop types, whether you’ve got a newer Greenstar 4000 or an older CDi model.
1. Built-in white filling key (older models)
Found on models like the Greenstar i or CDi Classic.
Steps:
- Insert the white plastic key underneath the boiler and twist to lock it in place
- Turn the grey tap next to the key slowly
- Watch the pressure rise on the display
- Once it reaches 1.3 bar, turn the tap off and twist the key back out
- Press reset on the boiler
2. Blue lever filling loop (keyless – newer models)
This is common on the Greenstar 4000 and some 8000 Life/Style models.
Steps:
- Find the blue lever underneath the boiler
- Flip the lever to allow water into the system
- Watch the gauge rise to around 1.3 to 1.5 bar
- Flip the lever back to its original position
- Press reset if needed
3. External filling loop (silver braided hose)
These are fitted on the pipework, usually under or next to the boiler.
Steps:
- Open both small valves at either end of the silver hose
- Water will enter the system, watch the boiler gauge
- When the pressure reaches 1.3 bar, turn both valves off
- Press reset on the boiler
Why does boiler pressure drop?
Boiler pressure can drop for a number of reasons, and most of them aren’t serious:
- You’ve recently bled your radiators
- A towel rail valve or radiator joint is slowly leaking
- The expansion vessel inside the boiler needs recharging
- Cold weather has caused pipework to contract
- Your system has lost water naturally over time
It’s completely normal to need a top-up once or twice a year. But if your boiler is losing pressure more regularly, it could be a sign of an underlying fault.
What to watch for before the boiler locks out
Often, your system gives you a few signs before pressure gets too low:
- Radiators not heating fully
- Gurgling or bubbling noises
- A warning symbol on the display
- A gauge that’s sitting near or below 1 bar
- Fault codes like EA, 118 or 1017
If you spot any of these, it’s worth checking your pressure and topping it up before it drops low enough to shut everything down.
When to call WLV Heating
If the pressure keeps dropping, even after topping up, it’s time for us to take a proper look.
During a pressure fault visit, we’ll:
- Inspect radiator valves, towel rails and joints
- Check all visible pipework around the boiler
- Test the expansion vessel and pressure relief valve
- Make sure the filling loop is secure and not leaking
- Run a pressure test to identify any slow loss in the system
In most cases, we can fix the issue the same day. And if not, we’ll always explain your options clearly so there are no surprises.
What happened with this customer?
In this case, the cause was simple, the customer had bled two radiators upstairs the week before, but didn’t realise they needed to top the pressure back up. We topped it up, checked the system over, and labelled the filling loop so they’d know exactly what to do next time.
No damage, no parts needed, no fuss.
Need help with a boiler that’s not firing up or flashing fault codes?
We’re happy to guide you through the steps, or pop out and take care of it for you.
Call us on 01902 283124
Or message us on WhatsApp 07395 088121
Visit our website: wlvheating.co.uk
WLV Heating, serving Wolverhampton, Walsall, Dudley & Birmingham
#WLVHeating #WorcesterBoschHelp #BoilerNotWorking #LowPressure #EAError #118Code #1017Code #CombiBoilerTips #WestMidlandsHeating
