Mustang007

Hi, I own a 1995 mustang V6 and I am having some probs with my speedometer. The speedo is electric driven and sometimes just doesn't even budge and sometimes works like if it never had problems. I checked under the car for the connection near the driveshaft and the was one. I unpluged it and pluged back went in my car and my speedo didn't work right away but after a bit he worked better than ever. But now he jammed again. Is there a way to fix that once and for all.

Thanks.