I have a 1990 Plymouth Sundance, bought it new, have had it for 16
years, it's getting a little long in the tooth but I've kept it up
mechanically and it's a good "running around town" car.

A couple of weeks ago, the air conditioning cut out. I took it to my
mechanic and learned that what had happened ... since he found this
part laying on the engine where it had come off ... was the plate
that's the front part of the clutch assembly (you have this plate, then
the clutch, then the coil, if that gives folks a better idea of what
I'm talking about) had broken.

Of course you can't buy just that plate. You have to buy the entire
clutch assembly. I tried the recyclers and they wouldn't sell the
clutch assembly separate from the compressor, which is understandable.

However, I found a clutch and compressor assembly from a recycler, with
a one-year guarantee, for a very good price and ordered it. I figured
"what the heck," my mechanic could take that plate off to replace my
broken one and if the rest of the clutch and compressor go out ... and
they're all in good working order, FYI ... I'll already have the parts
in hand.

The clutch and compressor arrived today ... and it's not going to work,
at least from the standpoint of being able to take the clutch plate off
and replace my broken one, because they're two different plates, even
the shaft that goes through from the A/C to the clutch is different. On
mine, there's a nut that holds the plate onto the shaft, along with one
other part that I'm going to discuss later. On this one, there's an
actual bolt that connects into the shaft, looks like it literally
screws in. I imagine what the deal is, this compressor/clutch is not
out of a 1990 Plymouth Sundance but will work on one if you replace the
whole unit.

I'm sure the next question is "why not replace the whole unit?" My
mechanic, who I trust completely from him working on my cars for years,
says he would prefer not to do that except as an absolute last resort,
because of the trouble in doing it, the fact that I'd have to recharge
the unit after just recharging the Freon in my current unit, and
because in his judgment it could touch off other problems elsewhere in
my A/C system.

So, I sat that aside and went to the local parts store and purchased a
new clutch assembly ... cost significantly more than the
clutch/compressor I got from the recycler, but I'm trusting my
mechanic's judgment on whether to change the whole thing or not ...
took it to my mechanic and he said it will work fine, but there's one
problem.

I mentioned that there's a nut that holds this plate onto the shaft
coming out of the A/C in my car. There was one other thing, a little
rectangular looking black metal pin, almost like a key pin or
something. You can see the notch for this pin on the clutch plate. My
mechanic says it fits onto the shaft to keep the plate steady. He says
if you don't have this, all the parts will wobble, etc., and the end
result will likely be tearing everything up.

The problem is, this little pin broke when the plate broke off on my
car. And there was not a new one included with the clutch assembly.

I'm sorry to be going so long in getting to the point on this ...
basically, can anyone tell me what this pin is called and how I might
go about getting another one, or if it's not possible to get another
one what might work as an acceptable substitute?

Because as I said, I'm trusting my mechanic's judgment in his opinion
that the best course of action here is just fixing the plate instead of
changing out the entire clutch and compressor. But if I can't find a
replacement for this little pin, I may have to change out the whole
thing and just keep my fingers and toes crossed and say a prayer.

Thanks in advance for any help.