1981 Triumph TR8 Automatic TransFACTORY OEM SERVICE PROCEDURE

THERMO Time Switch

  1. Using a thermometer, check engine coolant temperature. Compare coolant temperature with value stamped on thermo time switch body. Connect an ohmmeter between terminal "W" on switch and ground.
  2. If coolant temperature is higher than switch value, a very high resistance denoting an open circuit should be obtained. If coolant temperature is lower than switch value, a very low resistance denoting a closed circuit should be obtained. If switch does not respond as outlined, replace thermo time switch.
  3. If switch passes resistance test, allow coolant temperature to cool below stamped value on switch. With ohmmeter connected, connect battery power via an isolating switch to terminal "G". Using a stop watch, check delay time as ohmmeter changes between high and low resistance. Delay period should be as shown in Coolant/Delay Time Relationship chart. If not, replace thermo time switch.
Coolant/Delay Time Relationship

Temperature (Coolant) Delay (Seconds)
-4°F (-20°C) 8
32°F (0°C) 4.5
50°F (10°C) 3.5
95°F (35°C) 0
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.