Frymaster PROB Error Code

What does Frymaster PROB mean?

The controller has detected that the temperature probe (RTD) is reading outside its valid range or has produced an implausible value. This code appears on older Frymaster digital controllers and is functionally equivalent to a probe fault. The fryer shuts down heating and will not restart until the probe circuit is verified. Both a failed probe and a failed controller board can produce this code.

Symptoms

• Display shows PROB and the heat indicator light may be on without actual heating.
• Temperature readout is frozen, zero, or shows an extreme implausible value.
• Fryer enters lockout and will not resume heating.
• Error may reappear immediately after power cycling if the probe is open or shorted.

Common causes

• Failed RTD probe — open or shorted resistance element (most common cause).
• Loose or corroded probe harness connector at the controller or at the probe body.
• Damaged probe wiring — pinched, cut, or oil-soaked insulation causing a short or open.
• Controller board failure causing incorrect probe signal interpretation.

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Diagnostic steps

1. Power down the fryer

   Switch the fryer off and disconnect power before inspecting probe wiring. Allow oil to cool to a safe temperature before reaching into or near the frypot.

2. Inspect and reseat the probe connector

   Locate the probe connector at the controller terminal block. Pull the connector, inspect the pins for corrosion or oil contamination, clean with electrical contact cleaner, and firmly reseat. Restore power and check if PROB clears.

3. Measure probe resistance with a multimeter

   Disconnect the probe from the controller. Set the multimeter to Ohms and measure across the two probe leads. At room temperature (~70°F), an RTD probe should read approximately 113–115 Ω. Zero Ohms indicates a short; OL or infinity indicates an open — both require probe replacement.

4. Replace the probe if out of specification

   Install an OEM replacement RTD probe. Apply Loctite PST56765 thread sealant to the probe fitting before installation to prevent oil leakage into the conduit. Reconnect the harness and restore power.

5. Test the controller if the probe tests good

   If the probe reads within spec but PROB still appears, the controller board's probe-input circuit has failed. Document the probe resistance reading and contact Frymaster service for controller diagnosis and replacement.

When to call a professional

Contact Frymaster technical service at 1-800-551-8633 or fryservice@frymaster.com if PROB persists after installing a confirmed good probe. Controller board replacement requires a factory-trained technician for proper programming and calibration. Do not operate the fryer with an active PROB error — unmonitored oil temperature is a fire hazard.