The sender on the side of the thermostat has a wire that goes to a switch over valve behind the brake booster. pull the wire off the sender and ground it with a piece of wire. you will hear the switch over valve click. not sure what it was connected to, there is a rubber vac connector that had a line that went some where

before I improved on things

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There are 2 sensors on the left side of the engine. one between #1 & #2 injector and the other between #2 & #3 injector. the first one is for the temp gauge, and second one I believe is for the glow plug relay.
the sensor on the top of the thermostat housing has a wire the goes over to the right side, and posibly to the EGR modual behind the right foot well kick panel.
Charlie ☺