OK.

I removed the passenger side door check and compared it with my new one. They looked identical, with the exception being that the new one came with a plastic cover over the mechanism to keep dirt, debris, bugs, etc out.

I switched the passenger check over to the driver's side. Fit fine, and the door now closes.

Installed the new check on the passenger side. Fit fine, and the door now closes. The ONLY thing I did was remove the plastic shroud from the new door check before installing. The plastic shroud does not affect the mounting or operation of the door check in any way, it should not matter if it is left on or removed.

I have no explanation for this, but since my door checks are all now functional and I have no more nasty noises or unchecked doors, I will accept it.

Thanks for all the suggestions.

I know you are a big rivet advocate, but I've never used them on cars.. I've got a decent pop rivet gun, but have only used little aluminum rivets for small metal fabrication projects and fabric, what size and material of rivet do you recommend for auto-body repair? I've got a few non-structural locations that are a bit tricky to access that might be good candidates for riveting.

peace,
sam

__________________
"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)