ATAG fault code 303
Fault code 303 on an ATAG boiler (including I-series) means: PCB fault. Reset the appliance once. If the code comes back, a part is usually faulty. You can check the water pressure and settings yourself; leave work on gas-carrying parts to a certified gas engineer.
After a safety alert (gas, flue gas, combustion), reset no more than once and call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.
Cause
Fault code 303 on an ATAG boiler indicates: PCB fault.
Fixing fault code 303: step by step
- Note the exact code and the type of your appliance (see the rating plate).
- Check the water pressure (1.5–2 bar with the system cold) and that the appliance has power.
- Reset the appliance once. If the code comes straight back, do not keep resetting it.
- If the code comes back, choose the matching part below or have a qualified heating engineer take a look.
Applies to
ATAG I-series, i28CZ iCon1, i28ECZ iCon1, i32SZ iCon2, i36CZ iCon2, i36ECZ iCon2.
Click a model for the parts list and exploded view of that appliance.
Fault code 303 on other ATAG series
The same code does not mean the same thing on every series. Check the rating plate to see which series you have:
- 303 on P-series, P20C iCon1, P20EC iCon1, P27C iCon1, P27EC iCon1, P35C iCon2: Control unit fault.
Matching parts
ATAG parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.
Parts per Atag-series: A Series · i Series (iCon) · Q Series · E Series · P-series (iCon) · Blauwe Engel · XL-series.
For fault code 303, the part involved is usually in the category: PCB.
This message does not point directly to one faulty part. These are the parts that most often fit this appliance:
- Atag seal gas valve 3/4" € 19.71
- Atag sealing ring pump 1" 2 pcs € 20.39
- Atag O-ring set 2 pcs 21.89 x 2.62 mm plate heat exchanger € 23.79
Fix it yourself or call an engineer?
Always consult the manual for your appliance and work safely. If in doubt or if the fault comes back, call in a qualified professional. A question about a part? Write to us at info@instalpunt.nl.
Frequently asked questions
What does ATAG boiler fault code 303 mean?
PCB fault.
How do I fix fault code 303 on an ATAG boiler?
First check the cause described above. Then restart the appliance using the reset button. If the message comes back, a part usually needs replacing or the fault needs to be repaired by a qualified professional.
Which parts do I need for ATAG fault code 303?
That depends on the exact cause. In the ATAG parts overview at Instalpunt you will find the current price and stock for each part.
Can I fix fault code 303 myself?
You can reset the appliance and check things like the water pressure or settings yourself. Work on gas-carrying parts must be left to a certified gas engineer.
All ATAG boiler faults and codes at a glance →