|Adventures Under the Hood|
The Coolant Temperature Switch is located forward in the intake manifold's water jacket, on the side. It is a normally open switch that closes when the coolant temperature reaches a nominal 135° F.
Be aware that the computer will not go "closed loop" and assume control of the carburetor stepper motor until this switch closes and the Thermal Electric Switch (TES) in the air cleaner opens.
There is an easy and quick test (though not foolproof) for this switch.
If there is no change, the switch may not be closing.
If you are certain that the switch is good, but there is no change in engine speed when it's unplugged, there may be a broken wire in the harness somewhere. This needs to be attended to, since the computer will not operate until this circuit closes.