Pulled out the Tach to replace bulbs now only working occasionally
 

Searched the threads on Tach issues but none like the one I'm having. All I did was pull it out to replace the bulbs put it back in and now it works sometimes and other times it sticks in one place, other times not at all. When the weather is warm and the inside of the car is hot it will take some time for the tach to work this is common, but with cooler tempertures it always worked. Where do I start to look?
________
1981 SC

ground see if it came off the common ground connection under the dash, Kevin