71 Mark engine temp switch location

[1Bad55Chevy]

Currently the temp gauge is not working on my 71 mark. Looking near the factory coil location I see the temperature sending unit is connected but the connector is hooked to an additional 2 prong connector that is not connected to anything. I looked through the wiring diagrams and determined it is for the Engine Temp Switch (ATC only) which I can not seem to locate on the intake manifold. Where is this switch located? Additionally I have looked around the internet and have not found a 2 prong engine temp switch listed for this vehicle. Any help would be greatly appreciated!

[Dan Szwarc]

There should be something screwed into the intake near the upper water outlet.

[elcad70]

If your car has ATC it should have a two prong sender/sensor. What is the color of the wire going to the sender now? To my knowledge there is only provision in the intake manifold for one sender/sensor.

[1Bad55Chevy]

I can't really tell the color of the wires but I am going off this since the car is ATC.

I have both of those pig tails, the single and double wire connector. The switch in my intake is a single connector switch but the car is equipped with all the ATC components. I have not been able to locate the double terminal switch online but maybe I am not looking in the right places...

I new to the Mark iii so any help on this will be greatly appreciated!

[1Bad55Chevy]

I found this picture digging through really old post on this site.

work1.jpg (42.9 KiB) Viewed 186 times

So now I know where the switch is located but now the real questions are;
Did all mark iii's come equipped with both pigtails?
Does it matter which switch you use to make the temp gauge work? (Mine currently dosen't work but maybe the gauge is bad?)
Where do I buy the correct engine switch?

[TonyC]

The third question I can answer, with the route I took when I needed a new switch for my intake last year: E-Bay. Do a search with those key-words, there should be a lot of options pop up. The switch I ended up getting, a NOS part, was actually of a later period for later Fords, but because it was compatible with mine I took it...and I have not had one issue from that switch, no electric issues, no leaks. You may find one for a good price; many of the parts I got, I got for lower than the asking prices of the Usual Suspects...that is, unless a seller happens to be a Usual Suspect. Still, it has proved to be far more convenient for me, and 98% helpful.

---Tony

[LithiumCobalt]

The dual contact switch is also dual action. Anything below about 115 degrees, one side of the switch provides a ground signal to the ATC brain so that you don’t get a blast of cold air when you call for heat and the coolant isn’t warmed yet. The other side of the switch provides a signal to gauge and/or warning light for engine temperature. It does matter which terminal to use as they do two totally different things. Not sure about our Marks as I have not looked this closely yet, but on ‘67s, the red wire goes to the gauge/light and the white/green wire goes to the ATC.

[TonyC]

If the original (or an OE reproduction) harness plug is in place, and as long as that is connected to the car's wiring system correctly, then connecting the sensor is idiot-proof. The plug can only insert to the sensor one way.

---Tony

[elcad70]

Temperature gauge is red/white and ATC is yellow/white.