More Greenstars are installed in London homes than any other boiler, which is exactly why our engineers see every fault they produce, week in and week out. Same-day repair on EA lockouts, E9 overheats, low-pressure faults and everything in between, by Gas Safe engineers who work on Worcester Bosch daily.
Average reply under 10 minutes. No obligation.
Call 020 3000 0000Worcester Bosch is Britain's best-selling boiler brand for good reason: build quality is genuinely a step above most of the market, and when a Greenstar does fault it's almost always a discrete component, not a terminal problem. That means fast, sensible repairs for years past the point that cheaper boilers would have been scrapped. Alongside our wider London-wide boiler repair service, we run Worcester Bosch callouts every day of the week, and the patterns are consistent enough to diagnose most of them over the phone.
The single biggest winter caller is the EA lockout, an ignition or flame-detection fault that, on maybe eight jobs out of ten in a cold snap, turns out to be a frozen white condensate pipe running out of an exterior wall, not a fault inside the boiler at all. We tell people that on the phone before charging anyone a visit. Beyond EA, we see E9 overheat lockouts (usually a stuck pump, blockage or heat exchanger complaining after years of sludge), C6 fan-speed faults, D1 sensor errors, and quiet low-pressure faults that creep down over weeks until the heating stops firing. On older Greenstar CDi combis, still very common in London flats, the classic symptom is hot water working fine while heating dies, or vice versa: that's diverter valve wear, and we carry the parts.
The one Worcester Bosch weakness worth naming is scale on the aluminium heat exchanger of older Greenstar models in London's hard-water postcodes, which is exactly why annual boiler servicing pays for itself several times over on a Greenstar. Look after it, and it looks after you.
Worcester's fault display is one of the clearest in the industry, a letter and a number that map cleanly to a component. Below are the codes we clear most often in London homes. If your Greenstar is showing something else, call and read it to us; we'll tell you what it means for free.
The classic Greenstar fault. In winter, the first check is your condensate pipe, a frozen white plastic pipe running outside will trigger EA even though the boiler is fine. Thaw with warm (not boiling) water and reset. Persistent EA in mild weather = electrode, gas valve or flame sensor, engineer required.
Read our full Worcester Bosch EA guide →Stop resetting. Repeated overheat cycles damage the heat exchanger. Usually a stuck pump, an airlock, a blocked filter or scale build-up. Book an engineer before the fault becomes a replacement.
The fan is out of spec, worn bearings or a failing PCB signal. Replacement fans are stocked; usually a same-visit fix.
A cheap sensor with a big impact, the boiler runs blind on temperature. Straightforward swap.
The PCB is reporting itself unhealthy. Sometimes water ingress from a leak above it, sometimes end-of-life. Engineer diagnosis before ordering parts.
Repressurise via the filling loop to 1.0–1.5 bar cold. If it drops again within days you have a leak, a trace visit finds it in the hour.
Our engineers work across the current Greenstar 2000, 4000 and 8000 Life & Style ranges, the long-serving Greenstar i, Si Compact and CDi Classic / Compact / Highflow families, and the older Junior units still turning over in London rentals. Parts availability across the range is excellent, even for boilers pushing 15 years, most components are still stocked or next-day from Bosch's London depot. That said, on older Greenstars facing a heat exchanger or PCB job we'll always give you the honest repair-vs-replace numbers on site rather than sell you a big repair you'd regret in eighteen months. If replacement is genuinely the smarter call, see our new Worcester Bosch installation options.
Fixed quote before any work begins, 12-month workmanship guarantee, genuine or manufacturer-approved parts throughout. Real ranges below, where a job falls depends on the model and access, and we give you the number on site before we start.
"EA at 6am, family with a newborn. Diagnosed frozen condensate over the phone, told them how to thaw it safely, followed up with an insulation visit the same afternoon."
"Hot water fine, no heating. Diverter valve on the older CDi combi, engineer had the part on the van, fixed in one visit."
"E9 overheat on a two-year-old install. Turned out to be a sticking pump; still under Worcester's own warranty so we called it in for them rather than charge."
Greenstar-trained Gas Safe engineers across all 32 London boroughs, 24/7.