[ray_mcavoy]

Seeing as this problem started after you replaced the gauge, I'd recommend double checking it's ground connection to the cluster.

The temp gauge has 2 coils inside. A "hot" coil that pulls the needle to the hot side and a "cold" coil that pulls it to the cold side. Both coils share a common power feed connection.

The "cold" coil is grounded to the cluster housing through a resistor located on the back of the gauge. So a bad connection between the gauge and/or resistor and/or cluster housing (or an open circuited resistor) will prevent any current from flowing through the "cold" coil and pulling the needle to that side.

However, the "hot" coil is grounded through the variable resistance sending unit so current can still flow in that coil. And without any influence from the "cold" coil, that will result in the needle pegging to the hot side.