Alto-Shaam Combi Oven Error Code E90: Lower Gas Blower Not at Speed
E90 Lower Gas Combustion Blower Not at Speed means the lower combustion blower on a roll-in oven is running too slowly. Press the Start icon to acknowledge it, and have the blower and its cables checked.
High: combustion air is too low, so the oven cannot run safely on gas.
- Code
- E90
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC) roll-in models
What does Alto-Shaam error code E90 mean?
A gas burner needs a steady supply of combustion air, so each burner has a blower whose speed the control checks. On a roll-in gas oven the lower blower serves the lower burner. If it runs too slowly, the control posts E90 Lower Gas Combustion Blower Not at Speed and does not allow combustion to continue on weak airflow. The manual lists four causes: the power cable is not connected to the blower motor, the speed control cable is not connected, the blower motor is blocked or has failed, or the control board has failed. The first two are connection problems, which are often cheaper to fix than a motor. Pressing Start acknowledges the message and the oven then tries to return to normal operation, but the speed check repeats at the next call for heat. Low airflow can leave a burner burning poorly, so the control treats it as a stop.
Affected models and control systems
Alto-Shaam Combitherm CT PROformance and CT Classic roll-in gas combi ovens, such as the 10-20 and 20-20 sizes. E90 refers to the lower blower only.
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
- E90 Lower Gas Combustion Blower Not at Speed on the display
- Lower burner not lighting
- A weak or uneven blower sound near the base
Possible causes
Listed in Alto-Shaam's documentation
- Power cable not connected to the blower motor
- Speed control cable not connected
- Blower motor blocked or malfunctioning
- Control board malfunction
Other likely causes — what usually sits behind error code E90 on this control. A technician confirms which one it is before any part is replaced.
- Lint, grease or debris drawn into the blower inlet and loading the wheel
- A worn blower bearing that slows the motor as it warms up
Safe checks before calling for service
- Press the Start icon once to acknowledge E90.
- Look at the air intake near the base of the oven and clear any visible lint or boxes.
- Do not remove panels or touch the blower.
- If E90 returns, tell the technician whether the burner lit at all before the code appeared.
How a technician diagnoses error code E90
- Read the code and confirm this is a lower blower on a roll-in oven.
- Check the blower power and speed control cables at both ends.
- Spin the blower by hand with power off to find blocking or binding.
- Measure supply to the blower motor and its speed signal.
- Replace the blower only after the cables and control board output are proven.
- The blower is in the gas combustion path with live voltage on its wiring.
- Speed control signals are checked with a meter.
- A failed blower affects the safety of combustion.
How error code E90 differs from similar codes
E91 is the same speed check for the table-top or upper blower; E90 is the lower blower.
Technical reference
- Maker documentation
- Alto-Shaam owner support
- Edition
- MN-35949 Rev 08 03/22
- Models / control
- Combitherm CT PROformance (CTP) and CT Classic (CTC) roll-in models
- Section
- Error Codes, pp. 25-31
- 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.
Related Alto-Shaam combi oven error codes
Is E90 a gas leak?
No. It is an airflow check, but combustion should not continue on weak air.
Can I run the upper burner only?
The control does not allow the oven to carry on with the lower blower in error.
Could it be a loose cable?
Yes, two of the four listed causes are cables not connected.
Need help with Alto-Shaam error code E90?
A technician confirms the cause on site and gives you the price in writing before any work starts.