l have an older 1987 Sundance and recently I've noticed that the temperature gauge never moves even after standing overnity.It does not overheat or smoke but l do not wanna cause more problems by not fixing it.

Do not try to fix a problem that ai not there mate.if the car is running well just let it be.

If it does not move, it probably means its broken by the year of the car. you probably got your money is worth. go ahead and get it fixed. that part cant cost that much.

the thermostate is broken and l dont mean the little gauge inside the cars dashboard. its under the hood. once u replace that the gauge inside the cars dash will start to move again and act normal. it should only cost about a hundred dollars total for parts and labor.

Either the sending unit, or the gauge is bad. If should not be expensive to replace either. If the gauge is bad, you can get one from a junkyard

Well, then, fix it. It may be broken since it stays at the same reading after sitting up overnight. A good operating vehicle will rise to a certain temperature during driving based on what temperature of a thermostat u have in the car, and, assuming everything is operating alright, the gauge will stay in one position all during ur operating of it. But if it stays at the same reading after resting overnight, I'd give it a thump or two with my finger, nothing so serious that you'd break the glass or otherwise damage the gauge, & if nothing happens, go get it repaired or replaced. Even if a thump or two fixes the problem, watch for the gauge to stick again & consider going for a repair or replacement. It is good ur paying attention to such matters. The life of ur car, & the health of ur budget, requires u take care of problems while they're small & relatively inexpensive.

You have either a failed guage, a failed temperature sensor, or a broken sensor wire.

Get this repaired, it is important to know engine temp in order to avoid overheating and detect a problem with the engine is thermostat.