What would cause temperature gauge bouncing ?

my 2003 buick century did that. It was the battery!!

Popular Mechanics - Jan 1961 - Page 139 - Google Books Result

https://books.google.com/books?id=XNsDAAAAMBAJ
Vol. 115, No. 1 - ‎Magazine
Right, plates of full depth and weight ... Loose hold-downs - bouncing arounddamages a battery several ways ... Excessive loads - using the starter to move thecar should be only a ... ask for a temperature-corrected hydrometer reading, which should be 1.260 specific gravity. ... All this is dependent on the individual car.

Ask the Experts - USA Today

temp gauge bouncing around before going to center? ' Yahoo Answershttps://answers.yahoo.com/question/index?qid...Sep 28, 2013 - I called my mom and we switched cars and she didn't see anything ... Best Answer: If the temp gauge is literally "bouncing around" this is more ...Why is my temperature gauge jumping?Jan 1, 2013Temperature gauge bouncing.?Dec 18, 2008What does it mean, when my coolant temp needle jumps up and ...Oct 3, 2008My car temperature gauge keeps bouncing around from cool to red ...Dec 12, 2006More results from answers.yahoo.comTemperature Gauge Jumping Around an

There is a small voltage regulator on the back of the instrument cluster. Getting at it requires taking the dash apart. Not an easy job.

Either that or the gauge itself is at fault. I don't know your car specifically but the temp sensor on an engine is usually near the thermostat housing.

Might be. Could also be dropping because of the low RPM before the engine stops. What happens if you shift to neutral when you come to a stop ?

I would check that the battery terminals are tight as they may have been removed to do the switch If they have been removed then I suggest a cpu reset

definitely change it as soon as possible. maintaining your vehicle is important. the engine wears down faster without proper oil. Also just because it has oil doesn't mean its ok. old oil carries metal shaving from your engine. that's why you need to change it regularly.

only this link will help you to fix your problem http://toolsnyou.com/

have batterie and alternator tested

Probably the sending unit, and cost about $30.
The test of the gauges is to remove wire from sending unit and watch gauge go to lowest, then ground the wire and watch it go to highest.
If it does, then not a problem with gauge. So must be sending unit.