cooling issue or gauge/sender issue - temp guage reads high but car isn't hot

[RichMason]

dear group,

I'm chasing a temp issue and need some help. About two months ago, my car started reading hotter and hotter with the gauge moving between above the middle to the top mark and back down again, depending on how fast the car is moving/accelerating and the fans. I replaced both thermostats twice, flushed the system, replaced the coolant, then the radiator and a pressure test resulted in a replaced aux. water pump. I still have the same problem. My mechanic has been all over it with a digital thermometer, testing hose pressure, etc and he says it isn't getting hot anywhere on the engine. The fans kick on when the temp hits the highest white mark and the temp drops rapidly when they do about an eighth. I think the sender or the gauge are bad but I am also tempted by the voltage stabilizer, as my oil pressure guage flucutates (has a new sender) and my gas guage fluctuates, though not nearly as much as the temp gauge. Any suggestions?

[UconnTim97]

Cleaning the grounds behind the dash might help.

[1.2gees]

Those should help, but the engine bellhousing/batter grounds will help a whole lot more. Don't forget to stuff a rag in the inspection hole by the bellhousing before you go taking bolts off, caus eyou don't want to drop one down there.

Also another suggestion, don't replace parts that aren't proven to be faulty, unless you have no other options. This practice will be cheaper in the long run.
Ahmet

[RichMason]

Gauge was bad. I replaced the instrument cluster and it solved the problem. Also finally have my cruise control working. Mechanic was using a defective brain to test it! Somebody owes me some labor...