Volvo: Temperature Gauge on a 1970 240 DL Volvo

Question
Driving on the interstate, the temperature gauge will go almost to red line, and with no change, just with continuing driving, it will drop back to halfway, and then a little while later it will go back up to almost red line again, and then it drops back down to halfway. Sometimes it will go a long time without ever moving. It seems sporadic. But the car is NOT overheating. I open the hood, etc, and there is no steam, it's not overheating and it's not using any antifreeze. What now? What should I check? What should I do? Please help.

Answer
old car like that there are a few things but it seems electrical.I would check the wiring to the temp sensor which should be under the intake manifold ,if it is good i would replace the sensor .If that does not take care of it we will move on to the instrument cluster itself which is a bit nitorious for this condition .There are a few people out there that overhaul them and can be found on line .Usually things like dry joint and that kind of thing .Hopefully this helps ..later rob ..