This one bit me, so here’s a tip on replacing an Intermec PC43 printhead.
The printhead comes out very easily, you just move the blue catches on each side outward and it pops right out out.
There’s one connector that attaches the printhead to the printer and you need to remove that. The thing that bit me was getting the replacement printhead inserted properly. This is a side view of a correctly placed printhead:
What is critical here is that the body of the printhead has to be positioned inside the gap of the two plastic holders. A more obvious photo of one holder:
I would always line up the printhead with the guide posts and would miss getting the printhead inside of the gap.
If you get the printhead inside the plastic holders the guide posts will automatically line up. Press the printhead up against the springs until it clicks. Close the printhead assembly. If it’s difficult to manually pull on the label, you’ve done it correctly. If the label moves easily, you’ve missed the plastic holders; try again.