Thermo Switch

On P'UP models, continuity should exist when switch temperature is lower than 109-122°F (43-50°C). No continuity should exist when above 116-127°F (47-53°C). If switch does not operate properly, replace it.
On I-Mark models, there should be continuity when coolant temperature is 135-145°F (57-63°C) or higher. No continuity should exist when temperature is 127-140°F (53-60°C).

Fig 1: I-Mark Glow Plug System Wiring Diagram

Fig 2: P'UP Glow Plug System Wiring Diagram