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Occasionally, a burner may appear to be operating correctly, but it shows a slow recovery rate (discussed
on Page 1-18). The primary causes of this are low burner manifold pressure and misaligned or missing
deector targets. In some cases, the cause is a gas valve regulator that is out of adjustment. Refer to
Section 1.3.2 for instructions on checking the burner manifold pressure and Section 1.3.4 for adjusting
deector target positioning.
Improper Temperature Control
Temperature control—including that for the melt cycle—is a function of several interrelated components,
each of which must operate correctly. The principal component is the thermostat (in units equipped
with thermostat controls) or the temperature probe (in fryers equipped with other types of controllers).
Depending upon the specic conguration of the fryer, it may also include an interface board and
controller. Problems with improper temperature control can be categorized into those issues concerning
melt cycle malfunctions and those concerning a failure to control at setpoint.
Melt Cycle
In fryers equipped with thermostat controls, the melt cycle is controlled with a solid state melt cycle
board and a melt cycle switch on the control panel. In all cases, replace the defective component.
In fryers equipped with other types of controllers, the problem may originate in the controller, the
temperature probe, or a malfunctioning heat relay on the interface board. For problem isolation techniques,
refer to the troubleshooting guides, Troubleshooting the Thermostat and Troubleshooting the Temperature
Probe, in Section 1.7, Troubleshooting.
Failure to Control at Setpoint
In fryers equipped with thermostat controls, the problem will be in the thermostat. Refer to Section 1.3.5
for instructions on calibrating the thermostat. Possible causes are that
• the thermostat is out of calibration,
• the knob or exible shaft is loose on the thermostat shaft,
• a thermostat wire is disconnected or broken, or
• the thermostat is defective.
Refer to Section 1.3.5 for instructions on calibrating the thermostat. In fryers equipped with other types
of controls, the problem may originate in the temperature probe or probe circuit, the interface board, or
the controller. Refer to Troubleshooting the Temperature Probe, Section 1.7.4., for problem isolation
techniques.
Gas Valve Malfunction
Occasionally, a gas valve may malfunction. Use Section 1.7.2, Troubleshooting the Gas Valve, to
determine if the valve has failed.
Computer Malfunction
Before diagnosing problems related to a computer controller, it is important to understand the use and
signicance of sensitivity and recovery.