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Seatbelt Modules

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Ronzi,

Thank you for your response, but it is not exactly what I wanted. I'm looking for the wiring schematic of the module itself.

Kimberly
 
PAUL161 said:
Kimberly, check out this site. Maybe you can find what your looking for. I've never seen a diagram or schematic for a seat belt module. Your car must be a late model, right?

https://books.google.com/books?id=b55_ZAs...wF-0fEA#PPP1,M1
MGB Electrical Manual - Google Book Search
Click to expand...

I'm looking for module schematics for all years seat belt modules were used. The preview section of Rick's book does not cover the modules. I checked with my local public libraries to see if they had a copy of Rick's book. They only have the factory service manuals available for the MGB.

Does anyone know if the same modules were used on other British cars?
 
Isn't there a little diagram in the Bentley manual - back where all the big wiring diagrams are located? I'm not near one of my manuals but I sem to remember a little diagram on a page full of print.
 
There's nothing available for the guts of the module itself, sadly.

I'm in the process of troubleshooting/fixing one of these seatbelt delay units from a late Spitfire. My father-in-law is an ex-Bell Labs guru and has reverse engineered the circuit for me. Seems like a crude time-delay switching circuit.

A 555 timer IC could have handled this in a heartbeat, but instead there are some forty odd transistors/caps/resistors jammed inside the box. At least one of the transistors was leaking, so that got replaced. Buzzer is acting funky after 25 years in the sun so that will get a Digikey replacement.
 
Kimberly-

Did you find what you were looking for? Which module do you have? If is is a small black cube labeled "Pektron", I might be able to help.

My seat belt/dash warning light would not switch off causing the battery to drain every other week. I traced the issue back to this little black box. There were a couple of leaking transitors and a pair of bad electrolytic caps. All were replaced and it works as good as new.

Here is a schematic and a little test rig that my FIL build to help diagnose issues with the little devil. The test strip has switches to similate the door and buckle switches and a tiny light on the side for the dash.

I'd be happy to send you a copy of the schematic if you have the same type of module.

Seatbelt001.jpg


And the schematic; ignore the lower right bit, it is a subset.

Seatbelt003.jpg
 
Scott-

Thank you for the schematic.
I'm looking for any information on all the seatbelt modules, specifically the one used in the mid '70s interlock system.
What does the gearbox switch do? When is it open and when is it closed?

Happy holidays
Kimberly
 
Kimberly-

There are "interlock systems" comprised of individual switches/buzzers and then there are seatbelt modules.

I believe BL switched from discrete components to modules in about 1974 to meet US laws.

My 73 MGB has switches for the seats, seatbelts, gearbox and the drivers door. I also have a dashligh and a buzzer. Somewhere I have a wiring diagram for how this is wired, but I can't find it at the moment.

Modules were introduced in 74 with a starter interlock, and then relaxed in 75.
 
Kimberly said:
I'm looking for a schematic for the module shown on diagram 17 in the following link.
https://www.advanceautowire.com/mgb.pdf
Click to expand...

Can't help with that one specifically. Can you share any more details of what you're trying to do?

I believe that module has a single logic IC inside that controls the various functions. It was shared with the TR6 and probably a whole bunch of other British stuff of that era. I think this one actually controls the ignition as well = the car won't start if the belts are not buckled and the seats are occupied.

I believe the gearbox switch is normally closed and opens when the car is in any gear.
 
Scott-

I want to know what the power inputs and outputs are on the mid seventy's module.

Does the car have to be in neutral in order to start?
Are the seat switches momentary on or momentary off switches?

Ultimately I'm going to have to aquire a module and check it out.
 
Hi all.

Firstly thanks to Scott for his hard work and for posting the schematic. I am still trying to make sense of it. I suspect the diode at Pin 1 must be a zenner, or no current will flow when cranking, and there seems to be no path for the capacitor between pins 5 and 6 to discharge. Photos of the board would be helpful.

I have a '78 UK GT with a simpler two pin PEKTRON module. After breaking the glue and cracking it open I reverse engineered this schematic for it. It seems it is a 2.16Hz astable BJT flip flop driving a Darlington pair to cause the Fasten Seatbelt lamp to flash and catch the driver's attention. I assume the lamp is 2.2W, though it may be 1.5W. There is no buzzer.

PECKTRON_MGB_UK.gif

If you were talking of the interlock system with more than 6 pins, try this link:

https://www.mgexp.com/article/mgb/TSB/TSB 14 Pektron Seat Belt Interlock.pdf

Graham.
 
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