Check for trouble codes.
To enter diagnostic mode:
1. Turn ignition "ON."
2. Depress the "OFF" and "WARMER" buttons on the Climate Control Center (CCC) simultaneously and hold until the segment check appears on the Instrument Panel Cluster (IPC).
The following link will provide information on codes:
http://myweb.accessus.net/~090/dtcobd1.html
This may diagnose the problem.