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The thermocouple detects changes in temperature, but because of the short circuit it may fail to register the set temperature at the thermostat. This means the burner may not shut off. At the other extreme, the short circuit may occur in a place not shielded from the flue gases, which means the burner may shut off prematurely. These are the two conditions to look for in a shorted thermocouple. Deterioration from aging and from welding dissimilar metals together to for a junction introduces a contaminant that causes mechanical stress. Over time, five to ten years, metal fatigue from aging is certain. As a result, the temperature curve will vary. How To Replace A Thermocouple A heat shield protects the thermocouple from the burner flames and flue gases. Without the shield, the thermocouple would register flame heat to the thermostat instead of sensing the temperature of the griddle plate. To replace a thermocouple (refer to Figure 3), following this procedure: 1. Open the front panel to get access to the terminal board. 2. To withdraw the thermocouple, first remove the heat shield. It is held in place by two combination Philip and Robinson-heat size number 10 sheet metal screws. Remove the heat shield by sliding it down the wire. 3. A bayonet connector secures the thermocouple in place. Reach inside the hole and push and twist the bayonet connector a quarter turn. 4. Remove the connection to the terminal board and feed these wires through the heat shield. The thermocouple is now removed. 5. Connect the wires of the replacement thermocouple, but make sure the polarity is correct. Connect the negative red wires to terminal 7 on the thermostat and the positive white wire to terminal 8. (See schematic diagram). 6. Thread the thermocouple through the heat shield and into the plate cavity. SERVICING continued 7. The bayonet connector is spring loaded. Turn the connector so that it makes good contact with its seat on the plate, and adjust the spring so that at least 1” (25mm) of spring is available to push home. This is, it is loaded 1” (25mm) from the bayonet adapter. 8. Once this adjustment is made, remove the thermocouple from its cavity, pry the old heat sink material from the cavity and apply fresh heat sink compound (Garland Commercial Ranges part #77024). 9. Re-assemble the unit. Incandescent Lamps These lamps, similar in construction if not in shape to ordinary incandescent light bulbs, sometimes fail because of metallurgical breakdown of the light filament material. The green status light (PL1) should illuminate when the main switch SW1 is closed. • If PL1 doesn’t illuminate when SW1 is closed, replace it. • Failure of the amber lights (PL3, PL4, etc.) monitoring the zones cycle with the thermostat is not easy to detect. When on, an amber zone light is working. If it does not appear to light as part of the ‘burner on’ cycle, check. If the thermostat cycles the burner to be on, the PL amber light should illuminate. Pilot Ignition Control (Control Module) The Johnson G770 pilot ignition unit will lock out if the pilot flame is not sensed before the end of the ignition trial period and has to be reset. • To reset the ignition control, turn off the thermostat for a minimum of 30 seconds. SERVICING continued Figure 3 – Replacing a thermocouple BayonetadapterAdjust toabout 4.5" beforeinstallingAbout 1" before compressionGriddle plateProbe heatshield assembly Gas Valve Regulator The gas valve regulator (See fig 4) used on the griddle is AGA and CGA approved. The direction of gas flow is at right angles, right and left viewing the inlet. For setting the regulator: • For natural gas, Part #240510 regulator, set at 3.5” W.C. at 22 CFH air each side at 7” W.C. inlet pressure. Regulator adjustment range is 2.8” to 4.0” WC. • From propane, part # 245101 regulator, set at 10.0” W.C. Figure 4 – Gas Valve Regulator FlowFlowPressuresetting screwTurn counter-clockwiseto increas the pressuresettingTurn clockwise to decrease the pressureInlet Power Switches Dust caps fitted on the main power switch and zone switches protect them from dust and the corrosive effect of cooking fumes. If the dust caps are removed, or not replaced following servicing, the switches will deteriorate and have reduced life expectancy. Replace the dust caps following servicing. Control Circuit Figure 4 shows the control schematic for the GC-48 unit, which has two zones. The ignition and temperature controls for each zone are identical. SERVICING continued CONTROL PANEL SCHEMATIC DIAGRAM Figure 4 – Control schematic for a Model CG-48 Chain Griddle SERVICE BULLETIN #95-5 FROM – National Service Department BULLETIN NO. #95-5 TO – National Service Binder Holders DATE – February 24, 1995 Subject: Subject: Thermocouples used in the Chain Griddle Models CG-36, CG-48, CG-60 & CG-72 This bulletin supplements the chain Griddle Service Manual with a description of the basics of thermocouple theory and how to use the degree/millivolt tables issued as part of this b...

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