AccuTemp Steamer Error Code -99F: Shorted Temperature Probe
-99F on an AccuTemp Evolution electric steamer means the control sees the temperature probe as shorted. The reading is far below any real cabinet temperature, so the control cannot trust it. Cool the unit down, check power and the cabinet, restart once, and call us if -99F returns.
Medium: heating is unreliable, but the steamer can be switched off safely until it is tested.
- Code
- -99F
- Maker
- AccuTemp
- Equipment
- Steamers & kettles
- Applies to
- Evolution Electric steamer control board (E3/E6)
What does AccuTemp error code -99F mean?
On the Evolution electric steamer the control reads cabinet temperature from an RTD probe, a sensor whose resistance rises with heat. The control checks that resistance and compares it with a realistic range. A shorted probe or shorted wiring drives the resistance toward zero, which the control would interpret as an impossibly cold cabinet. It then shows -99F where the temperature belongs. Because no real cabinet sits at that temperature, the control concludes the sensor circuit is broken rather than the steamer being cold, and it stops trusting any heat decision based on it. The steamer may refuse to heat, or it may behave unpredictably until the reading returns to a normal range. The check happens constantly, not only at startup, so a short that appears when a wire shifts with heat can bring the message up in the middle of service. The message does not describe the heating elements or the water level; it describes the probe circuit alone.
Affected models and control systems
This applies to AccuTemp Evolution electric 3-pan and 6-pan steamers with the E3/E6 control board, as covered in the Evolution Electric service manual. Gas and propane Evolution models and other AccuTemp lines use different tables.
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
- -99F shows where the temperature should be
- The steamer will not heat, or heats erratically
- The message appears mid-service after running normally
Possible causes
Listed in AccuTemp's documentation
- Probe wiring pinched or burned inside the steamer
- RTD probe shorted in the cooking cabinet
- Probe connector on the control board loose or wet
- Probe input circuit on the Evolution control board damaged
Other likely causes — what usually sits behind error code -99F on this control. A technician confirms which one it is before any part is replaced.
- Probe wiring rubbing on a sharp panel edge near the cabinet wall until the insulation wears through
- Water getting into the probe connector after a heavy wash-down of the cabinet area
Safe checks before calling for service
- Power the steamer down and wait for the cabinet to cool.
- Check the power and the breaker.
- Look at the cabinet for standing water or debris you can reach safely without opening panels.
- Switch the steamer on once.
- If -99F returns, stop using it and call us. Tell us whether the steamer had just been washed down, because moisture is a common reason for a short.
How a technician diagnoses error code -99F
- Confirm -99F is steady, then power down and lock out the steamer.
- Trace the probe wiring for pinching, burn marks or a wet connector.
- Disconnect the probe and measure its resistance at room temperature.
- Measure across the wires to see whether the short is in the probe or the harness.
- Replace the probe, harness or board only after the reading isolates it, then test a full heating cycle.
- A short inside a wire bundle or probe cannot be found by eye and needs resistance readings taken with a meter.
- Checking the board's probe input means live voltage inside the control area, which is not safe for an operator.
- Damp connectors can read as a short and then dry out, so the problem can seem to vanish and return without being fixed.
How error code -99F differs from similar codes
-1F on this control is the opposite reading: an open probe circuit rather than a shorted one. The cause is in the same circuit.
Technical reference
- Document
- AccuTemp Evolution Electric Service Manual SP8026-2508 p.14
- Maker documentation
- AccuTemp owner support
- Edition
- SP8026-2508 (page footer; the PDF file name says SP8027-2508)
- Models / control
- Evolution Electric steamer control board (E3/E6)
- Section
- 3.1 Troubleshooting Table, printed pp. 14-15 (ref letter E: -1F / -99F; ref letter F: water level board LED D3, p. 15-16); flowchart p. 13
- 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 AccuTemp steamer & kettle error codes
Can I keep running the steamer with -99F showing?
No. The control cannot read real temperature, so heating is unreliable and we would not cook with it.
Could water in the cabinet cause -99F?
Yes, moisture at the probe or its connector can read as a short, but it still needs a technician to confirm and dry it properly.
Is -99F a failed board?
Not necessarily. The probe and its wiring are more common culprits, so the board is replaced only after those test good.
Need help with AccuTemp error code -99F?
A technician confirms the cause on site and gives you the price in writing before any work starts.