Vulcan Hart PROB

What does Vulcan Hart PROB mean?

The PROB display indicates the fryer controller has detected a fault in the temperature measuring or control circuit. This means the RTD temperature probe or the controller board itself has failed, and the unit can no longer reliably monitor frypot temperature. Heat demand is disabled and the fryer will not operate until the fault is resolved.

Symptoms

• PROB appears on the digital controller display and the fryer will not heat.
• Continuous alarm sounds from the controller.
• All cooking cycles are cancelled and operator buttons are disabled.
• Frypot remains cold regardless of setpoint selection.

Common causes

• Failed RTD temperature probe (open or shorted circuit).
• Damaged or disconnected probe wiring harness.
• Corroded probe connector pins causing intermittent signal loss.
• Faulty controller board unable to read probe resistance.
• Probe positioned incorrectly or dislodged from frypot bracket.

Diagnostic steps

1. 01

   Power cycle the controller

   Press the ON/OFF switch to power down the controller, wait 30 seconds, and power it back on. A transient electrical surge can sometimes trigger a false PROB fault; a reset clears it if no hardware failure exists.

2. 02

   Inspect the probe wiring and connector

   Shut off power and follow lockout/tagout procedures. Unplug the temperature probe connector and inspect both the connector and wiring harness for corrosion, burnt insulation, or loose pins. Clean corroded pins with electrical contact cleaner and reconnect firmly.

3. 03

   Test probe resistance with a VOM

   With power off and probe disconnected, measure resistance across the probe leads using a digital multimeter. At room temperature (77°F), the RTD probe should read 90,000–110,000 ohms. A reading of zero or infinite resistance confirms probe failure.

4. 04

   Verify probe seating in the frypot

   Drain the frypot and confirm the probe is fully seated in its mounting bracket inside the tank. A dislodged probe will read an erroneously low temperature equivalent to an open-probe fault.

5. 05

   Replace the temperature probe if out of spec

   If resistance values fall outside the acceptable range, install a replacement probe of the correct part number for your fryer model. Tighten the compression nut securely and reconnect the lead wire connector before restoring power.

6. 06

   Replace or service the controller board if probe tests good

   If the probe tests within specification but PROB persists, the controller board itself has failed. Contact an authorized service center — the board is a factory-configured unit and is not field-programmable.

When to call a professional

If replacing the probe does not clear the fault, or if multimeter testing indicates the probe is functioning correctly, the controller board has failed and requires replacement by an authorized Frymaster/Vulcan-Hart service technician. Controller boards are model-specific and factory-configured; incorrect board substitution can result in uncontrolled overheating. Call your authorized servicer before attempting board replacement.