Coolant Temp Not Reading

1991 S10 4.3L (Z) automatic, 4x4.

So, I have a digital dash panel (sucks!) and the coolant temperate never registered. (Bought the truck about 2 months ago and didn't notice it at first).

Anyway, I checked the plug and it was broke and corroded. So, I replaced the coolant temp sensor itself and tried cleaning the plug (rusted/corroded). Well, it didn't help but about a week later the coolant gauge started working but said the temperature was at full and overheating but it was not. Then it went really low (couple of bars) then back to blank again. Has done nothing since then.

So, I pulled the plug and replaced the connector with my own connectors. Instead of the pigtail connector I used 2 small wire connectors that would attach to the 2 connectors on the sensor. I made sure they did not touch and short out. They are separated with a silicone sealant. Well, that didn't do anything either.

Any ideas why this gauge does not work except for the one random time that it did work?

By the 'pegged hot' reading, dried out broken wire too.