Are the terminals on the cartridge burned or they are just greasy?
If they are not damaged then just clean them (do not forget to turn off the circuit breaker).
Remove the cartridge, take it apart and check both heating elements for continuity (Here are the complete instructions
How To Check Continuity With Ohmmeter ).
- The part number for the large heating element is
AP2027820
- The part number for the small heating element is
AP2027821
Gene.