SYSTEM TESTING See Figures 1, 2, 3 and 4 Fig. Fig. 1: Glow plug system schematic Fig. Fig. 2: Dropping resistor and glow plug relay locations Fig. Fig. 3: Thermo switch location Fig. Fig. 4: Dropping resistor check To test the dropping resistor, check for continuity across the terminals as described in the illustration. If no continuity exists, replace the unit. 1. To test the thermo switch, first remove the switch. Submerge the end of the switch in water and raise the temperature gradually. The switch should be off at 126-140°F (53-60°C) or lower. The switch should be on at 134-145°F (57-63°C) or higher. If not, replace the switch. 2. REMOVAL & INSTALLATION See Figure 5 Fig. Fig. 5: Location of the glow plugs The glow plugs are located under the injection nozzles, and are threaded into the cylinder head. Disconnect the negative (-) battery cable. 1. Disconnect the glow plug and unscrew it from the engine. 2. To install: Lubricate with anti-seize compound before installing the plug. 3. Install and tighten the plug to 65 ft. lbs. (88 Nm). 4. Reconnect the plug wiring. 5. Connect the battery cable and check operation. 6.