Hey there Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
Hello…joined the forum awhile back…this is my first new post. Have been slowly semi-restoring a '78 B. Also have a '54 TF that I did a frame-off restoration back in the mid-60's and owned and drove B-GT's as daily drivers into the late '70s....so MG's have been a part of my life for a long time. Was recently sent out to pasture (a bit unexpectedly) but now have time to see about getting the two piles of English iron filling up my garage back to operating condition.
Awhile back someone asked a question about the switches located in the seat cushions. I have been chasing the seat belt system on my B...and note there is just a single driver side seat cushion switch on my car. There is no wiring from the loom to connect a passenger seat switch...but that is only the beginning of the mystery. The leads from the driver side switch connect to a pair of wires coming from the bundle behind the console (brown/purple and black). I researched the schematics for B wiring and discovered this circuit seems to go nowhere. The brown/purple and black wiring appears on the schematic in both the Haynes manual and the Bentley book... but there is no driver seat cushion switch in the circuit...one end of the pair terminates in a symbol for the typical two circuit connector...and the brown/purple wire runs apparently up to the right side of the engine compartment near the large plastic connector that joins the four heavy brown wires together...the two circuits servicing the lights and the fuse block. But there is just a plain little dot at the end of the brown/purple wire on the schematic. My car actually has a small stub of the smaller gauge brown wire protruding from the wiring loom where two of the larger brown wires emerge...but it has no voltage on it and seems unrelated to a brown/purple mate through a missing line fuse. No brown/purple stub appears on any part of the loom in the engine bay.
I e-mailed the tech folks at Moss in California about this anomaly...and they did not have any information on it. Going back to the '73-'74 North American wiring schematic published in the Haynes manual, brown/purple circuitry is indeed used for a variety of functions...two seat cushion switches, the buzzer and the seat belt warning, all serviced by a brown/purple wire originating near the fuse block through a line fuse. It was all handled by a fairly complex (12 external contacts) sequential seat belt control unit. The more simplified module (6 contacts) used in the later cars handles a wire from the driver's side seat belt switch...but there is no indication of a brown/purple wire in any of the circuitry related to the seat belt system. I'm having some trouble with the module functioning correctly and suspect some component failure...I've developed a schematic of the internal circuitry and am pursuing replacement components which I'll report on if I am successful.
So...after all that...was the post '73-'74 driver seat cushion switch connected to the car's electrical system at all or was it a hangover from an earlier design that just never got re-integrated into the new module design? Since the vendors appear to offer no replacement module for later cars, are we left to sort out problems in the original components? Does anyone care about them? My research indicated a seat-belt system recall was issued for ’77 cars onward…but the module was not involved…seemed misunderstanding of how to handle the belts was more the issue.
I would agree that ignoring this wiring and switch probably resolves any operational concerns, but from the purist's perspective, I sure am curious about what those guys in Abingdon intended.
Bill
Awhile back someone asked a question about the switches located in the seat cushions. I have been chasing the seat belt system on my B...and note there is just a single driver side seat cushion switch on my car. There is no wiring from the loom to connect a passenger seat switch...but that is only the beginning of the mystery. The leads from the driver side switch connect to a pair of wires coming from the bundle behind the console (brown/purple and black). I researched the schematics for B wiring and discovered this circuit seems to go nowhere. The brown/purple and black wiring appears on the schematic in both the Haynes manual and the Bentley book... but there is no driver seat cushion switch in the circuit...one end of the pair terminates in a symbol for the typical two circuit connector...and the brown/purple wire runs apparently up to the right side of the engine compartment near the large plastic connector that joins the four heavy brown wires together...the two circuits servicing the lights and the fuse block. But there is just a plain little dot at the end of the brown/purple wire on the schematic. My car actually has a small stub of the smaller gauge brown wire protruding from the wiring loom where two of the larger brown wires emerge...but it has no voltage on it and seems unrelated to a brown/purple mate through a missing line fuse. No brown/purple stub appears on any part of the loom in the engine bay.
I e-mailed the tech folks at Moss in California about this anomaly...and they did not have any information on it. Going back to the '73-'74 North American wiring schematic published in the Haynes manual, brown/purple circuitry is indeed used for a variety of functions...two seat cushion switches, the buzzer and the seat belt warning, all serviced by a brown/purple wire originating near the fuse block through a line fuse. It was all handled by a fairly complex (12 external contacts) sequential seat belt control unit. The more simplified module (6 contacts) used in the later cars handles a wire from the driver's side seat belt switch...but there is no indication of a brown/purple wire in any of the circuitry related to the seat belt system. I'm having some trouble with the module functioning correctly and suspect some component failure...I've developed a schematic of the internal circuitry and am pursuing replacement components which I'll report on if I am successful.
So...after all that...was the post '73-'74 driver seat cushion switch connected to the car's electrical system at all or was it a hangover from an earlier design that just never got re-integrated into the new module design? Since the vendors appear to offer no replacement module for later cars, are we left to sort out problems in the original components? Does anyone care about them? My research indicated a seat-belt system recall was issued for ’77 cars onward…but the module was not involved…seemed misunderstanding of how to handle the belts was more the issue.
I would agree that ignoring this wiring and switch probably resolves any operational concerns, but from the purist's perspective, I sure am curious about what those guys in Abingdon intended.
Bill
A friendly reminder - be careful what links you click on here. If a link is posted by someone you don't know, or the URL looks fishy, DON'T CLICK. Spammers sometimes post links that lead to sites that can infect your computer, so be mindful what you click.