Check the connector at the back of the gauge cluster. Sometimes merely pressing
moderately hard on the gauge cluster with your thumbs will reconnect things, but
be careful not to crack the clear plastic lens. Otherwise, you'll have to remove the
cluster and clean the connector and put it back.
Also, check the ground wires on the passenger side of the engine block, to the left of
the oil check dipstick tube. Those wires are short and taught and, over the years,
engine vibes will often fatigue the wires and cause them to break or fall off of the
ring connector end.