Water Temperature gauge not working/what is this?

[Lazerwolf]

Been struggling to get my factory water temperature gauge working in the 74 Charger. One option I'm exploring is adding a secondary after market gauge in addition to the factory one. Reading through several older posts, if seems there should be a "plug" in the top of the water pump to remove by the heater hoses. However, looking at mine, it looks almost like there is a vacuum ports there. Guessing this wasn't factory in the 400 engines and someone added it in the last 40 years. Anyone know what this is and/or if it can be removed as a place to add a temperature sensor.

 

[Dennis H]

Can't help but get a laser temp gun in the meantime so you know what is going on.

 

[Icecobra]

I know that's a temp control for a vacuum switch. I don't know what it hooks to but that's what it is and uses water temperature to open and close the port...

 

[Meep-Meep]

What you see is a thermo vacuum switch to control vacuum advance. It's for emissions reasons. Your actual temp gauge sensor is right under that facing the radiator.