Alto-Shaam Combi Oven Error Code E28: B10 Point 3 Probe Failure
E28 B10 - Point 3 - Core Temperature Probe Multipoint Fault means sensing point 3 of the multipoint core probe, B10, is defective or disconnected. Press the Start icon to acknowledge it and have the probe checked if the message returns.
Low: sensing point 3 of the core probe is out of use; cooking by time is unaffected.
- Code
- E28
- Maker
- Alto-Shaam
- Equipment
- Combi ovens
- Applies to
- Combitherm CT PROformance (CTP) and CT Classic (CTC)
What does Alto-Shaam error code E28 mean?
The control can read each sensing point of the multipoint core probe B10 separately. If the third point gives an open, shorted or absent signal, the control posts E28 B10 - Point 3 - Core Temperature Probe Multipoint Fault. The manual lists two causes, a failed probe or miswired or disconnected wires, so the work is to decide whether the problem lies in the probe itself, the cable or the oven's receptacle wiring. Pressing Start acknowledges the message and the oven then tries to return to normal operation, but any program that cooks to core temperature will test the probe again. A single point message with other points reading normally points at one broken line in the probe, not at the oven. If all points fail at once, the receptacle or its wiring is a more likely place to look. This message applies only to the CT PROformance and CT Classic tables.
Affected models and control systems
This is a CT PROformance or CT Classic code, covering the 6-10, 10-10, 7-20, 10-20, 20-10 and 20-20 combis in electric and gas.
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
- E28 Point 3 message on the display
- Core probe cooking not available
- One probe reading dropped while others display
Possible causes
Listed in Alto-Shaam's documentation
- B10 probe malfunction
- B10 probe miswired or wires disconnected
Other likely causes — what usually sits behind error code E28 on this control. A technician confirms which one it is before any part is replaced.
- A wire inside the probe cable broken from repeated bending at the strain relief
- Mineral residue on the plug contacts from steam and rinse water
Safe checks before calling for service
- Press the Start icon once to acknowledge E28.
- Unplug the probe, check the plug, and push it back in fully.
- Do not use the probe if the cable is cut or the tip is bent.
- If E28 returns, report which point numbers have appeared and cook by time.
How a technician diagnoses error code E28
- Read the code and note any other point messages.
- Examine the probe and cable; clean and reseat.
- Check continuity of the third sensing line with a meter.
- Inspect the receptacle and its wiring to the control.
- Replace B10 once a broken line is confirmed.
- Meter tests on probe lines need the probe isolated.
- Receptacle wiring is near live control voltage.
- Probe accuracy affects food safety.
How error code E28 differs from similar codes
E26, E27 and E29 are points 1, 2 and 4 of the same probe; E22 reports B10 as a whole.
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
Does E28 mean the whole probe is bad?
It points at sensing point 3; other points can still be fine.
Can the probe be repaired?
Not by an operator; a failed line normally means replacing B10.
Will the oven still cook by time?
Yes, the core probe is not needed for time programs.
Need help with Alto-Shaam error code E28?
A technician confirms the cause on site and gives you the price in writing before any work starts.