Speedometer,odometer, and trip counter shuts off if sitting in rain 1988

Hi, I have recently noticed on my T-Bird that when the car sits out in the rain and is not being run that the speedometer, odometer, and trip counter will not move at all, but after running for a bit all of it seems to kick on at the same time. The check engine light has not come on about this, so I was just wondering if anyone has had this problem or knows how to fix it, is it something as easy as removing the connection at the firewall and putting some dielectric grease in it, or replacing the ground wire or is their some more serious work that needs to be done? Any help would be very appreciative
 
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