Gas boiler error codes (E01, F5, F.28…): the complete guide and when to call a technician

When your gas boiler shows an error code, it has detected a problem and put itself in safety mode. The code isn't the fault — it's the safety system telling you something needs attention before heating can safely resume. This guide covers the most common codes on the brands sold in Morocco (Ariston, Vaillant, Saunier Duval, Bosch), what you can safely try, and when you must call a technician right away.

How to read a boiler error code

A code usually starts with a letter (E, F, A or d) followed by a number. The letter tells you the category:

• **E** or **F** = blocking fault, the boiler is stopped until repair
• **A** = warning, the boiler runs but something needs attention
• **d** = diagnostic mode (showing readings, not a fault)

The number identifies the type of problem. Different brands use different numbering for the same fault — check the model manual, or send a photo of the code on WhatsApp to be sure.

The six main code families

Most codes belong to one of six families. Recognising the family already tells you whether you can act yourself or not.

1. Flame and ignition errors

The most common in Morocco. Examples: **E01, E1, F1, F.28, F.29, A01** depending on the brand. Means the boiler tried to fire but didn't detect a flame, or the flame went out mid-run.

Possible causes:

• Gas supply cut off (check the gas valve or the butane bottle if you use one)
• Low gas pressure in the network
• Fouled or failed ignition electrode
• Faulty gas valve
• Carbon build-up on the burner

What you can try: make sure the gas valve is open, then press the Reset button once. If the code returns immediately, don't repeat — call a technician.

2. Water pressure errors

Examples: **E10, E11, F22, F.22, A02** depending on the brand. The boiler monitors heating-circuit pressure (usually between 1 and 2 bar). If it drops or climbs too far, it stops.

Possible causes:

• Small leak on a radiator or pipe
• Water top-up needed (natural loss over time)
• Safety valve draining continuously
• Deflated expansion vessel

What you can try: check the pressure gauge. If it's below 1 bar, slowly open the filling valve until it reaches 1.5 bar, then restart. If pressure drops again quickly, there's a leak — call a technician.

3. Sensor and temperature errors

Examples: **E20, E28, F.75, F76** depending on the brand. A temperature sensor (flow, return or DHW) is sending an inconsistent value.

Possible causes:

• Sensor fouled by scale (common in hard-water areas)
• Loose electrical connector
• Faulty sensor that needs replacing

What you can try: nothing safely — these faults need instrument measurement. Call a technician.

4. Fan and flue errors

Examples: **F32, F33, E15, F.75** depending on the brand. The fan drawing combustion air, or the flue path itself, is blocked or faulty.

Possible causes:

• Balanced flue outlet blocked by leaves or a bird's nest
• Faulty fan
• Failed gas pressure switch

**Safety warning:** if the flue is blocked, there's a risk of carbon monoxide (CO) building up inside the home. Don't override the safety system and don't repeat restart attempts. Call a technician immediately.

5. Combustion and heat-exchanger errors

Examples: **E36, F.62, A07** depending on the brand. Problem at the heat exchanger or with combustion quality.

Possible causes:

• Fouled heat exchanger (carbon deposits)
• Pierced heat exchanger (must be replaced — expensive)
• Incorrect gas setting

What you can try: nothing. These are specialist faults.

6. Control board errors

Examples: **E99, F.85** or codes very specific to the brand. The control board doesn't respond or returns inconsistent values.

These faults usually require replacing the board, which is an expensive part. Sometimes the cause is simple: a loose connector or moisture. Nothing to do yourself.

Quirks of the brands sold in Morocco

Each brand uses its own numbering. The list below summarises the families, but the exact number varies by model:

• **Ariston**: codes starting with E (E01, E02, E10…). Errors 1-9 usually mean flame/temperature, 10-19 water pressure, 30-39 heat exchanger.
• **Vaillant**: codes starting with F (F.22, F.28, F.75…). F.22 = low water pressure, F.28 = flame not detected, F.75 = pressure switch or pump.
• **Saunier Duval**: same system as Vaillant (same industrial group) — F.22, F.28, F.75 mean the same thing.
• **Bosch**: codes starting with E or A (E9, A2, E3…). E9 = exchanger or sensor, A2 = flue.

In every case: send the photo of the code to your technician on WhatsApp. A clear image saves an hour of diagnosis.

What you can safely try before calling

Safe steps for the end user:

1. **Check water pressure** on the gauge (should sit between 1 and 2 bar).
2. **Check the gas valve is open** and that the bottle (if you're on butane) isn't empty.
3. **Press Reset once only**. If the code returns, don't repeat — the safety system is protecting you.
4. **Photograph the code** and the model reference (plate on the side of the boiler) and send them on WhatsApp.
5. **Watch for any gas smell** — if the odour is strong, cut the gas, open windows, leave, call from outside.

When the danger is real and can't wait

Call a technician immediately (don't restart yourself) in these cases:

• Clear gas smell or hissing leak sound
• Burning smell or smoke near the boiler
• Headache or dizziness when standing near the appliance (possible CO)
• Hot water leaking heavily from the boiler
• The code came back immediately after two consecutive restarts
• Any code related to the flue or exhaust path

How to request an efficient intervention

When you call, this information speeds up the visit:

1. **Brand and model** (on the silver plate next to the boiler)
2. **The code shown** (WhatsApp photo preferred)
3. **How long since the fault started** (today, last week, since winter…)
4. **Is there hot water?** Is heating partially working?
5. **Last annual servicing** (if you remember the date)
6. **Exact address** (neighbourhood and street, especially in Ouarzazate or Agadir)

These points let the technician bring the likely parts on the first visit and often prevent a second call-out.

Prevention: annual servicing

Most faults that trigger error codes can be avoided with good annual servicing before winter (September-October): burner cleaning, heat-exchanger check, combustion tuning, gas-safety tests and CO measurement in the flue gases. These operations significantly reduce breakdowns and extend appliance life.

If your gas boiler in Morocco hasn't been serviced in more than two years, faults are likely to appear soon. Message us on WhatsApp to book a service before the cold season — better that than an emergency on a cold night.