Temperature gauge not working.

[99MMountaineer]

Hi, I just bought this vehicle, V8 engine. Seller said loose wire.

I think... there are two temp sending units?
One is above t hermostat on left side of engine when looking from the front.

And another is on the right, My Haynes book says the one on the right is a EEC IV sending unit? What does that mean?

I took some pics under the hood, the one on the right, is this is? looks like it is only one wire is that right?

Which one, left or right, causes the gauge not to work?

How would you troubleshoot, repair?

Any advice is appreciated.

 

[BrooklynBay]

The single wire sending unit is for the gauge/light.

 

[BrooklynBay]

Ground the single wire on the sending unit to see if the gauge moves to the overheating range. This will help you determine if the gauge or the sending unit (or both) are bad. Did you check the fuses?

 

[99MMountaineer]

I found a drawing online, not eactly our engine but it shows ETC or engine coolant temp sensor on left, and a Water Temp sensor on right... I guess those are the two I am looking at?

Brooklynbay said the single wire unit was for the gauge/light, I um... do you mean that is the one that goes to the gauge? so that is the issue? Can you explain more please?

Which one would be the cause of the gauge not working?

And any idea why there are two? What is the purpose of the other one?

 

[99MMountaineer]

Ground the single wire on the sending unit to see if the gauge moves to the overheating range. This will help you determine if the gauge or the sending unit (or both) are bad. Did you check the fuses?

Sadly, no... there is a fuse it could be?

I used to work on cars a lot when I was young... I am out of practice. Thanks for the help.

 

[BrooklynBay]

The engine coolant temperature sensor has a couple of wires. It's a temperature controlled variable resistor to tell the computer what the coolant temperature is. This will provide feedback to adjust the air/fuel mixture. The single wire variable resistance sensor varies the resistance to ground which is the engine block.