AccuTemp Steamer Error Code -1F / -99F: Probe Reading Lost
On an AccuTemp Evolution gas or propane steamer, -1F means the temperature probe reads open and -99F means it reads shorted. Either way the control has lost its temperature reading. Let the unit cool, check power and water, restart once, and call us if the number returns.
Medium: the steamer cannot regulate heat, but shutting it off removes the risk and nothing else is affected.
- Code
- -1F / -99F
- Maker
- AccuTemp
- Equipment
- Steamers & kettles
- Applies to
- Evolution Gas/Propane steamer
What does AccuTemp error code -1F / -99F mean?
The Evolution gas steamer watches cabinet temperature with an RTD probe, a sensor that changes resistance as it heats. The control checks that resistance continuously and expects a value in a believable range. If the circuit is broken, the reading runs off the top and the display shows -1F. If the circuit is shorted together, the reading collapses to the bottom and the display shows -99F. The control prints -1F / -99F in place of the temperature, and from that moment it is managing the burner without any picture of how hot the cabinet is. The owner's manual says to call for help when either number appears, and that is the right call, because the steamer cannot regulate its heat and may not heat normally. Both numbers point at the same circuit: the probe, the wire that carries its signal, and the input on the control. What differs is only how that circuit has failed. The burner, the gas valve and the water supply are separate systems and are not what this message reports.
Affected models and control systems
This applies to AccuTemp Evolution gas and propane steamers covered by the Evolution Gas/Propane service manual. Electric Evolution steamers use a separate manual and control board, and older controls number their messages differently.
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
- The temperature area shows -1F or -99F
- The steamer heats poorly or not at all
- The cabinet never reaches working temperature
- The reading returns after each restart
Possible causes
Listed in AccuTemp's documentation
- Probe wire connection at the control loose or broken
- Probe failed, with its resistance outside the expected range
- Control board probe input failed
- Probe lead damaged by heat
Other likely causes — what usually sits behind error code -1F / -99F on this control. A technician confirms which one it is before any part is replaced.
- A probe lead near the burner compartment that has been baked brittle, so the conductor cracks and then touches the shield
- Condensation in the probe connector that bridges the two contacts and reads as a short
Safe checks before calling for service
- Switch the steamer off and let steam release and the cabinet cool.
- Confirm the unit has power and the water supply is open.
- Switch it back on once and watch the display.
- If -1F or -99F appears again, stop and call us.
- If you ever smell gas, step outside and phone the gas company before anything else. Tell us which number showed, since it tells us whether to hunt for a break or a short.
How a technician diagnoses error code -1F / -99F
- Note which number shows, since -1F and -99F send the technician toward different failures.
- Check the probe lead and connector for heat damage, moisture or a pinch, with the gas and power off.
- Measure the probe resistance against the manual's table at a known temperature.
- Test the board input by substituting a known resistance.
- Replace the probe or board only when the test points at it, then confirm normal heating.
- -1F and -99F come from one circuit, and telling a break from a short takes meter readings.
- The probe lead runs near the burner compartment, so testing it means working around gas and live voltage together.
How error code -1F / -99F differs from similar codes
This page covers the gas and propane Evolution. The electric Evolution lists -1F and -99F as separate entries, and its manual page differs.
Technical reference
- Document
- AccuTemp Evolution Gas/Propane Service Manual SP8026-1902 p.23
- Maker documentation
- AccuTemp owner support
- Edition
- SP 8026-1902 (current revision 1902, prior revision 1201)
- Models / control
- Evolution Gas/Propane steamer
- Section
- 3.1 Troubleshooting Table: -1F / -99F printed p. 16; Ignition (Spark) Module LED indications (ref letter L) printed p. 24
- 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
Does -1F mean something different from -99F on a gas steamer?
Yes. -1F means the probe circuit is open and -99F means it is shorted, but both mean the control cannot read temperature.
Can I cook while the number is showing?
We advise against it. With no temperature reading the control cannot manage heat, so results and safety are not dependable.
What if it comes back after a restart?
Then the cause is still in the circuit. Stop using the steamer and have the probe, wiring and board input tested.
Need help with AccuTemp error code -1F / -99F?
A technician confirms the cause on site and gives you the price in writing before any work starts.