Temp Guage Not Working

[BIGFOOT]

Just changed my thermostat on my 1995 Tahoe 5.7l. Now the temp guage doesn't work, but was before.

There are 3 wires that are grounded to one of the studs on the thermostat covering. They had to be replaced because the nut was frozen to the stud. I put nice new eye connectors on, even tested them directly to the ground and the guage still won't work (but I do not know if these grounding points are related to the guage).

So, how do I diagnose why my temp guage isn't working? All of the other guages are working properly.

Thx.

BF

UPDATE: I realizzed that the heater is not getting hot. So I am starting to believe I have an air bubble in the system. What is the best way to bleed the bubble out?