Coolant Temperature Lower Than Switch Rating

1. Disconnect negative battery cable and thermo time switch connector. Connect an ohmmeter between terminal W of thermo time switch and ground.
2. A very low resistance (continuity) should be measured. Apply 12 volts to terminal "G" of thermo time switch.
3. Measure time delay between applying voltage and the ohmmeter reading changing from low to high resistance. Time delay should be as specified. See XJS THERMO TIME SWITCH DELAY  table in this article. Replace switch if it does not meet specifications.

XJS THERMO TIME SWITCH DELAY

Coolant Temperature °F (°C)	Switch Rated 59°F (15°C)	Switch Rated 95°F (35°C)
14 (-10)	5.7 Secs.	6.5 Secs.
32 (0)	3.5 Secs.	5.0 Secs.
50 (10)	1.2 Secs.	3.5 Secs.
68 (20)	N/A	2.0 Secs.
86 (30)	N/A	0.5 Secs.
95 (35)	N/A	0.0 Secs.

Fig 1: Location of XJS Engine Sensors & Components of "P" Type Electronic Fuel Injection System

Courtesy of JAGUAR CARS, INC.