Seat Belt Buzzer System on a 72 Cuda: need an explanation

[72CustomCuda]

Hey folks,

First of all, thanks to everyone for all the help ya'll have given me thus far.  The people on this forum are priceless.

Latest quest:  get the "fasten seat belts" light to work on my 72 Cuda.  72's did not have the ignition interrupt system...just the buzzer and the dash light. 

For reference, when I say butt detector below I mean the item pictured here:
http://www.cuda-challenger.com/cc/index.php?topic=68731.msg704811#msg704811
It's under the seat...

First:  The light works...connect one blue wire to one of the light prongs, ground the other prong, good solid fasten seat belt lighting. 

Second: The buzzer works...keep the same blue wire connected to one prong, GROUND the second blue WIRE that goes to the light...buzzer comes on. 

Third: I only have a harness connection to the actual butt detector that's underneath the seat on the driver's side, but I pulled the butt detector itself off my passenger seat.  Is this normal?  Am I missing a butt detector or was it standard on 72's to only have it under the passenger seat?

Fourth:  The harness connector with a blue wire and a gray wire on the driver's side kick panel area...have power coming through the blue wire...but the ground doesn't appear to be good as my test light doesn't come on when I use it to complete the circuit.  I'm ASSUMING the gray wire is the ground...yes?  From what I can tell in the wiring diagram, the gray wire simply makes a straight shot back to the seat belt relay. 

So my problem lies probably in the seat belt relay...Any tips on how to test it?

[Jamiez]

I only know the 1974, but there are 2 connections for each seat.  One of the weight detector which connects to the bottom of the seat, the other to the bottom of the seat belt clasp on the trans tunnel.   The wiring runs from the driver's side to the passenger side and the under seat connectors are fed up through holes in the carpet.  I know someone had shoved mine way down in there and it was a challenge to locate the driver components of the harness.  You might need to pull the seat and lift the carpet to get at it.

Most wiring harnesses in the e bodies do NOT have a ground wire.  The body is used for ground.  It has been a while since I messed with the seat belts, but I would be surprised if any of the wires in that harness are ground.

The relay is shared with the horn if I remember correctly.  Does the horn work?  Also a lot of people hated the seat belt lights/buzzers and would break off or bend the leg of the relay that goes to the seat belt circuit.  I'd inspect the relay itself for signs of tampering.   If it is the relay they are pretty cheap and should be available from just about anywhere (unless you're picky and need a OE penstar logo one).

[72CustomCuda]

The 72 didn't have the connectors to the seat belts themselves, just the butt detectors, but the path from drivers to passengers side makes sense. 

The car has been completely restored with the few exceptions I'm working on here, and to install the sound system I had the seats out and the carpet up, so there's not anything hiding.

The key in buzzer is shared with the horn relay.  The horn works and I also just got a brand new relay from Roseville.  The buzzer doesn't go off when the key is in, but I'm thinking that's probably related to the fact that there's no key in buzzer switch in the column...haven't checked that yet. 

The seat belt buzzer is separate and located to the right of the glove box.  If the grey wire is not the ground, then I either have a bad relay or the relay is not properly grounded.  I would lean towards a bad relay.