Middleby Marshall PS360 102, Component Checks Reset System After Lockout, Check Spark Ignitor

SECTION 3 - SERVICING COMPONENTS

9.Component Checks Reset System After Lockout

If the oven enters safety lockout, the system must be reset before attempting further operation or checkout. The system will remain in safety lockout until it is re- set. Shut system OFF. (Turn Heat switch OFF.) Wait at least five minutes, then turn Heat switch ON.

10.Check Spark Ignition Circuit

The electronic module and step-up transformer in the ignition module provide spark ignition at 15,000V (open circuit). This circuit can be checked at the ignition module as follows:

a.Turn OFF the gas flow at the manual shutoff valve.

b.Disconnect the ignition cable at the ignition mod- ule terminal to isolate the circuit from the pilot burner/ignitor sensor, and prepare a short jumper lead using heavily insulated wire, such as a spare ignition cable.

c.Energize the ignition module and touch one end of the jumper firmly to the control board ground termi- nal (GND). Do not disconnect the existing ground lead. Move the free end slowly toward the stud terminal to establish a spark and then pull the lead wire slowly away from the stud. Note the length of the gap at which arcing stops.

d.An arc length of 1/8” (3.2mm) or more indicates satisfactory voltage output. Replace the ignition module if no arc can be established or if the maxi- mum gap is less than 1/8” (3.2mm), and power to the ignition module input terminals was correct.

WARNING

Do Not touch either stripped end of jumper or stud terminal. This is a very high voltage circuit and electrical shock can result. Perform the test im- mediately upon energizing the system, before the ignition module enters safety lockout and inter- rupts the spark circuit.

11.Check Spark Ignitor

If the troubleshooting procedure indicates a problem with the ignitor/sensor, check the spark ignitor and the ignition cable connections and continuity as follows:

Check Ignitor/Sensor

a.Check the ignitor spark gap to make certain it is correct, 1/8” (3.2mm). If necessary, use a needlenose pliers and carefully bend the tip of the outer electrode to the correct gap.

b.Check that the pilot flame is properly adjusted. Check Igniton Cable

a.The ignition cable must not touch metal surfaces or current-carrying wires. Use ceramic standoff insulators, if necessary.

b.Check the length of the ignition cable. It must not exceed 3 ft. (0.9 m).

c.Check the connections to the ignitor and ignition module terminals. All connections must be clean and tight. Loose connections may not conduct a flame current even though the ignition spark is sat- isfactory. Check the electrical continuity of the cable. Replace the cable if it is damaged or dete- riorated.

d.If no spark or a weak spark occurs, but the spark ignition circuit checked normally, disconnect the ignition cable at the ignitor/sensor and measure the arc from the cable end to the ignitor stud. Fol- low the same general procedures and observe the same cautions as in Step 10, Check Spark Igni- tion Circuit, above.

If the arc is correct, replace the ignitor/sensor.

If the arc is less than it should be, disconnect the igni- tion cable and use a jumper wire from the ignition mod- ule stud terminal. If the spark is normal, replace the ignition cable. If the arc is still smaller than normal, replace the ignition module.

Q. Checking the Gas Pressures

All gas pressures should be checked using a manometer at the supplied pressure taps, as follows:

•Inlet pressure can be checked at the inlet pressure tap on the combination gas valve. See Figure 72 (on Page 98).

•Regulated pressure can be checked at the outlet pres- sure tap on the combination gas valve. See Figure 72 (on Page 98).

Current PS555/570-series ovens provide an additional regulated pressure tap in the main gas line, just before the line enters the burner. This allows you to connect a SECOND manometer downstream of the modulating valve to check that the valve is functioning properly. We encourage you to use this tap to diagnose prob- lems with the modulating valve whenever possible.

•Pilot gas pressure can be checked at the pilot pres- sure tap. For ovens with a Wayne burner, the tap is located on the pilot line. For PS360EWB/WB70 ovens with a Midco burner, the tap is located on the end of the pilot orifice fitting. Refer to the illustrations on Pages 88-90.

Some older ovens (pre-1994) with Wayne burners may not be equipped with a pilot pressure tap. If you en- counter problems with an erratic pilot (see Servicing the Combination Valve on Page 98), it may be neces- sary to install a tap. Middleby offers Service Kit P/N 30185 which includes the pilot pressure tap and in- structions. A copy of the instructions are also provided in the Appendices section.

IMPORTANT: Any older oven that has a pilot pressure tap installed should have the combination gas valve re- placed with a current version at the same time. Com- bination valves used prior to 1994 are beyond the scope of this Manual and may not be compatible with the tap.

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