I just bought this used with only 83K miles on it. Runs great. Looks nice. One problem: the lights on the instrument cluster (spedo, tach, gas, etc.) aren''t working. The rest of the cluster (check engine, door ajar, etc.) does. The dimmer switch works to turn the dome lights on and off, and I''ve just finished replacing the bulbs in the dash to no avail. All the fuses are fine. I have no other problems with this truck. What could be the problem?