It sits on 100 about 25 seconds and then starts rising up around 230.
it was going to 260 as soon as I turned the ignition switch on or very soon afterwards.
I’m not sure what changed!

 

Ok, what is the coolent level? Is this happening static or engine running?

 

Static.
I replaced the head gaskets (had oil in the coolant). Replaced the sending unit because it was broke. Added radiator flush and water. When I started it to run and flush the system, I noticed the gauge pegged immediately. I replaced the sending unit again thinking it was bad. I didn’t fill the system back up with water yet to finish flushing. Trying to figure out the gauge issue.
All that being said, the system is low and I have been checking it with the key on and not running.

 

I'd suggest refill, burp the system, then check it. If it was pegging immediatley, now takes 20-30 seconds, could be just low coolent flow. Correct that first, then go from there.

 

I flushed the system and it’s completely full.
while it was running, I plugged in the sending unit and it immediately pegged out at 260 degrees.

 

Okay, I'm really confused now.
The system has been flushed and it is now full. When I turn the key switch on, the gauge sits on 100 deg. for approximately 25 seconds and then goes to around 240 deg. Then, when I start the truck, it immediately pegs out at 260 deg. I inserted a 150 ohm resistor in the connector to ground and the gauge read approx. 155 deg., then I inserted a 210 ohm resistor and it read around 130 deg.. I believe that proves that my wiring back to my gauge, including my gauge is good. My next step, I replaced the Connector, started it up and it pegged out at 260. I bought, for the third time at a different store, another sending unit. Start the Truck and it goes to approx. 140 degrees and never moves. I ran the Truck for 2 hours and the gauge never moved.
Can someone please help!
I have bought 2 new sensors that max out at 260 degrees when the Truck is started and 1 new sensor that reads approximately 140 degrees and never moves.

 

No one has suggested a gauge stepper motor problem - I know nothing about that except it appears to be a very common problem in other threads relating to gauge problems. Smarter folks please comment on this!! If I am reading correctly the gauge is pegging on a cold engine

 

I don’t think 95 Chevrolet 1500 has a stepper gauge motor.

 

I'm sure it dose'n't, but good input anyway. Revist why you replaced the sending unit ? Is the problem now as it was?

 

The sending unit was broken off flush were the plastic goes into the housing