The thermoswitch or coolant temperature switch is located just to the right of the throttle body (red arrow). You will need to drain the coolant level to below the switch; usually, removing the coolant from the expansion tank is enough (yellow arrow). If you need additional help please see our article on .
1. Check the thermoswitch for continuity when the engine is just above normal operating temperature (probe the connector on the thermoswitch and the engine block itself). If continuity is not present, the thermoswitch is bad and must be replaced.2. If the thermoswitch is good, check the underhood relay by switching it for one like it (possibly for the clutch interlock). If the cooling fans now work (or, if you used the clutch interlock relay and now the car won't start) then replace the fan relay.3. If both the thermoswitch and relay are good, replace the radiator fan itself.
To replace the switch you will need to drain the coolant level to below the thermoswitch, but you do not need to drain it completely. Usually, removing the fluid from the expansion tank is enough, as the radiator is below the level of the thermoswitch and will not flow back up into it. Even removing the expansion tank fluid, you should be ready for some spillage of fluid and catch and dispose of it in accordance with your local regulations. If you have not replaced or flushed your system in over two years, this is a very good time to consider performing this work as well.
The Mishimoto Thermoswitch Fan Switch replaces your OEM S2000 fan switch, allowing your radiator fan to activate at 80°C / 176°F degrees, 15°C / 59°F degrees lower than stock temperature. This will help prevent heat soak and prolong the life of all the components in your engine bay. Installation is simple with direct replacement to OEM switch.
East Peoria, Illinois, USA
1968 MG MGC GT