Attached to gray case containing control circuit board (shot, heater relay burned hole in circuit board) is a ceramic part with two posts attached. Is this a thermal fuse or is it a current fuse? . I am not an expert, but this piece appears to contain a diode (one end pointed and green. ) One wire attached is black and the other, going to door switch, is black and white. In removing leads I did not pay attention to which lead went to which post. Does this part have an electrical direction and if so which wire goes to which lead? Also, if this is a thermal fuse, is its purpose to cut power if circuit board overheats or catches fire?
Thanks.

The original fuse did not blow when heater relay failed.. Is it okay to install original fuse back by "clipping" fuse into gray box containing new control board? Is there a reason to replace fuse and wiring harness when new control board installed. I ordered control board, but not a new fuse with wires as original still works.