1987 DT150 - Water Flow Sensors

[TGFish]

Good Day,

I'm slowly working through my inherited DT150SS and had the cover off the rear ignition coil holder and noticed two male connectors loose. I determined they were one each from the water flow sensors. Both were the short, black ground wires. The female connectors where the male grounds should be inserted, were the violet/white wires from the left and right flow sensors. According to the service manual, the '87 sensors had only two wires (Left: G/R and Black Ground, and Right: G/Y and Black Ground). So I suspect the sensors were replaced at some juncture. The two-wire units appear to have been replaced by the the three-wire sensor -the v/w wire sending a temperature signal incorporated into the sensor. Additionally, the v/w wire, as seen in the attached image, looks like it has a variable resistor symbol which makes sense for the temperature reading part of the unit. Looking for a second opinion: Am I thinking right to believe I can leave the v/w wire disconnected and connect the black from the sensor to the black ground?

[Solarman]

That variable sensor is a temp sensor for the powerhead, it should be connected just as the diagram shows, there might be one for each side (right and left cylinder banks) located near the thermostats. If the powerhead sensors are wired to other wires (to computer) then the v/w wires may not be needed. Your specific yr/model motor wiring diagram may have been revised, or the exact parts weren't available, maybe changed to available parts? I don't know the history of your motor?

The powerhead sensors should indicate the motor is running hot, before the cooling water sensors open.

The cooling water sensors only open if the temp gets too high.

Good luck, post back on what you find out.

[TGFish]

Thank you. A little further reading in the service manual on the "L" Models (1990) has a note that the temp sensor was incorporated into the flow sensor. Sometime after 1990 I'm guessing the previous owner changed out the sensors with the available parts, but attached the male end of the temp sensor wire (V/W) incorrectly to the black female ground. I'm going to follow the service manual wiring diagram and hook up accordingly. Appreciate the help.