Box Interchangeability

[DerekTheGreat]

Keep in mind the Lincolns were built in a different plant than the Fords and Mercs. "Design change" does not necessarily translate to "we used up all the old stuff".

That said, there are significant wiring differences between an 89 and a 90 (even Ford and Merc), just on that note, the cornering lamps are fed off the turn signal switch with no relays on a 90...

The body harnesses were assembled by someone, and not as a single piece. So you have different people assembling different pieces of harnesses which are then shipped to the assembly plant and put in the cars and plugged into each other. During the harness building process they will run out of the round sockets and start using the flat ones, without regard for what exact car those sockets are going into.

There has to be some consideration for it as the owners manual of a particular year says the bulbs it uses. I never thought to check if my manual actually says different bulb types for tails and front signals. Will check when I'm in that car again.

Well aware, Wixom MI to be exact Up to a certain year of course, forget when that was but beyond my interest since those things were no longer motivated by pushrods.

Manuals aren't always accurate either. The GMC one for our '88 truck wasn't in regards to bulb use.

[VicCrownVic]

Well shit in my hat and spoon feed it to me.

I thought it was silly Ford switched the bulbs for '89 with the Town Cars, considering the update that was coming for 1990 it was like, why bother?

Fuel level sending unit was changed for '89 TC as well. One year part which physically fits in place of the older stuff but behaves (same resistance range) like the newer stuff. I guess I can't say that I'm surprised they would make other changes for '89 despite the aero TC being introduced for 1990.

[kishy]

Well aware, Wixom MI to be exact Up to a certain year of course, forget when that was but beyond my interest since those things were no longer motivated by pushrods.

Manuals aren't always accurate either. The GMC one for our '88 truck wasn't in regards to bulb use.

Just coming full circle on the bulb weirdness...the 1991 owner's manual specs 3157 for tail/brake/turn, and 2357A (which is an amber, round-base bulb) for front turn signals.

It's weird, but it's factory spec.

[gadget73]

Thats probably accurate. My 91 Mark VII runs wedgie bulbs in the back, but I think its round base up front. I couldn't tell you what the manual says about it though.

[DerekTheGreat]

Wedgie bulbs, haha.
I never had to replace any of the bulbs in Ashley's TC except for the ones in the tail panel when we swapped it. Old panel had wedgie bulbs for the reverse lights and new panel ('85-'87 style) had the roundies. Harness connector was the same so that was a plus at least. Didn't even pay attention to her ditch lights when I stole the housing to replace my busted one.
I also own a '91 Mark VII. Have a spare driver's side fender you'd like to sell? Or know someone who does??? Seems to be all I need to get this damn thing on the road! Would make a cool birthday present for Ashley...