Temputure gauge fluctuates when car is at operating temputure

An accurate temperature gauge will always fluctuate because the temperature in the engine fluctuates.

Usually the only time this is really noticeable is when the engine has been working hard and suddenly has to wait at a junction or similar and the gauge can rise considerably.

You didn't mention by how much the gauge fluctuates?
As long as it remains approximately in the normal zone it is acceptable but if it climbs into the hot zone or falls into the cold zone it is not acceptable and the cause should be investigated as soon as possible.

poor coolant flow water pump? air lock in system? bring to operating temp shut down than open air bleed screws.

have a mechanic test the oil pressure with a mechanical gauge
it is more than likely that the electric sender unit has failed and is sticking internally
the tic noise could be a relay working from an intermittent power supply or bad ground

The rough running is the cause of the voltage gauge movement.. As the engine speed increases and decreases the voltage output of the alternator goes up and down. So the gauge is a symptom not a problem.

no,,, fluctuations mean =low oil pressure,oil level low,oil old or too thin viscotly,oil pump loosing or not develloping the correct pressure
pressure release valve spring weakened

possn u have bad fan motor or relay or bad therostat

My 2000 chevy s-10 starts fine and I get 14.5 on my batt. gauge.after driving it a bit it drops to 10.5 to 11.0. when I am at a stop light the batt. gauge goes to 10.5 to 11.0....When I go down the road again the batt. gauge goes back to 14.5.What could be the problem?

did you ever resolve this. mine is doing the same thing exactly

I'm thinking the coolnat level is low, and this might be caused by a bad head gasket - At least $800 to fix - sorry.

The sending unit for the oil guage will cause the oil guage to fluctuate this is caused from some sludge build up that is more than likely stuck in the sending unit tube. Use Gunk motor flush on your next oil change this should help the oil guage problem.( make sure you read the direction on the back of the bottle)
As for the check engine light you can take it to Auto Zone and have them scan the computer. Sometimes the EGR valve will build up with carbon causing the valve to stick slightly open which will make the idle on the car fluctuate up and down. Its also possible you need O2 sensors.