Temp Gauge Reads Low

[flatsix]

I thought the previous owner intalled a 160 thermostat so I installed a new 195 but the gauge still reads about 170 deg. It stays fairly constant when warmed up but does go up slightly then back down fast. Could I have a bad gauge or could something else be going on. I also changed the temp sender with no change. Truck is a 98 Tahoe 5.7 with 48K

 

Any ideas?

 

thanks

[greyghost03]

It could be a bad gauge or maybe the sending unit you just bought might be defective? My temp gauge went out in my truck recently- dealer had to replace sending unit.