Convotherm Combi Oven Error Code E34.0: Boiler Pump Failure

What does Convotherm error code E34.0 mean?

The steam side of a combi oven depends on a pump that moves water into the boiler. The control starts the pump when the boiler needs water and checks that the pump responds and that water arrives. If the pump does not turn on or does not deliver, the control displays E34.0 Boiler pump fault and stops steam operation, because a boiler running without water would overheat. On the older Convotherm OES, OEB, OGS and OGB ovens, the same number is described as a steam generator pump that does not turn on, so the principle is the same on both lines. The manual's first response is a power reset: unplug the unit for about 10 seconds so the control restarts and re-checks the pump. That clears an error caused by a one-time glitch. If the code returns, the pump, its wiring or its driver on the control board needs testing, and that cannot be done from the front of the oven.

Affected models and control systems

Convotherm 4 (C4) floor-standing combi ovens, from the UL / USA operating manual; the same number is also listed for the older OES, OEB, OGS and OGB ovens, whose own manual calls it a steam generator pump that does not turn on.

Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.

What you may notice

• E34.0 Boiler pump fault on the display
• No steam, or steam that stops soon after it starts
• Pump not humming when steam is called for
• Oven finishes dry-heat programs but not steam ones

Possible causes

Likely causes — what usually sits behind error code E34.0 on this control. A technician confirms which one it is before any part is replaced.

• Boiler pump seized or worn out
• Wiring or plug to the pump loose
• Pump driver on the control board not switching
• Air or scale restricting the pump inlet

Safe checks before calling for service

How a technician diagnoses error code E34.0

1. Read the E34.0 code and history to see how often the error returns.
2. Confirm that water is available to the pump and the inlet is not blocked.
3. Check the pump connector and measure the voltage on the pump when it is commanded on.
4. Test the pump itself for a seized or open winding.
5. Inspect the boiler and lines for scale that increases the load on the pump.
6. Replace the pump or the control board output only after the voltage and winding tests.

How error code E34.0 differs from similar codes

On the older OES, OEB, OGS and OGB ovens the manual calls E34.0 a steam generator pump that does not turn on. After the 10-second restart it adds a second step, disabling steam generator rinsing, before contacting customer service.

Technical reference

Maker documentation

Convotherm owner support

Edition

9761695_06 engUSA 05/22

Models / control

Convotherm 4 (C4 easyTouch / easyDial, incl. Maxx pro); Convotherm OES / OEB / OGS / OGB (older, pre-C4)

Section

6.2.1 Error codes (Errors and required responses), pp. 105

Checked

October 2026

We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.