Alto-Shaam Combi Oven Error Code E91: Upper Gas Blower Not at Speed
E91 Upper Gas Blower Not at Speed means the table-top or upper combustion blower is running too slowly. Press the Start icon to acknowledge it and call for service if it returns.
High: the blower is too slow for safe combustion, so the burner will not run.
- Code
- E91
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC)
What does Alto-Shaam error code E91 mean?
The combustion blower feeds air to the burner, and the control measures how fast it turns. If the table-top or upper blower runs under its required speed, the control posts E91 Upper Gas Blower Not at Speed. Without enough air a gas flame can burn poorly, so the oven stops rather than continue. 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. Pressing Start acknowledges the message and the oven then tries to return to normal operation, but the next call for heat repeats the speed check. This code is the upper twin of E90. On a table-top oven it names the only blower. On a roll-in oven it names the upper one, and a separate message covers the lower blower. Look for a connection problem before assuming the blower itself is bad.
Affected models and control systems
Gas CTP and CTC ovens in sizes 6-10 to 20-20. The number belongs to the blower of a table-top oven, or the upper blower of a roll-in oven.
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
- E91 Upper Gas Blower Not at Speed on the display
- Burner not lighting or shutting off quickly
- Blower sounding slow or labored
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 E91 on this control. A technician confirms which one it is before any part is replaced.
- A blower wheel coated with grease and dust from kitchen air
- A cable plug loosened by vibration since the last cleaning or service
Safe checks before calling for service
- Press the Start icon once to acknowledge E91.
- Make sure the area around the oven's air intake is open and free of lint or boxes.
- Do not remove panels to inspect the blower.
- If E91 returns, note whether the oven was recently moved or cleaned.
How a technician diagnoses error code E91
- Read the code and note whether the oven is table-top or roll-in.
- Check both blower cables for seating and damage.
- Turn the blower by hand with power off to find drag.
- Measure power and speed signal at the blower connector.
- Replace the blower or control board only after the cables test good.
- The blower circuit carries live voltage inside the gas compartment.
- Speed signals can only be judged with a meter.
- Combustion air is a safety item on gas equipment.
How error code E91 differs from similar codes
E90 is the lower blower on roll-in ovens, E91 the upper or table-top blower; both share the same four causes.
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)
- 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 E91 about gas supply?
No, it concerns the combustion air blower speed.
Which blower does a table-top oven have?
One blower, covered by E91.
Can dirt cause it?
Yes, a blocked blower is a listed cause.
Need help with Alto-Shaam error code E91?
A technician confirms the cause on site and gives you the price in writing before any work starts.