I own a 99 Caravan se and have had a similiar problem. After investigating the instrument cover, I located my problem behind my fan and temperature control cluster. One of the connections had obviously overheated and caused the side of the connector block to melt which caused the connection to not be made. This eventually caused the instrument cluster to start acting up. I would loose the speedometer, gas gauge, engine temp indication, etc. I went to the automotive store and picked up a single connector. I then used a utilty knife to carefully cut away the plastic to remove the bad connection from the block connector. I cut the bad wire and installed the new single connector on it and then slipped the connector over the pin on the back of the cluster.
Not sure what caused the plastic to melt in the first place, but it's been good till now.
Hope this helps.