This is the seatbelt warning system from my 74 XJ12. I removed it because I can't stand government tyranny. Kidding.

It seems pretty self contained, some wires to the seat belts and cushion sensor for each seat, then some lights and power and ground. The only wire (white yellow) I'm wondering about is one that goes to starter solenoid --do you think that's a no start interlock (if it's removed/disconnected)?

The seat belt system has a constant/battery voltage to the unit so maybe that wire connected to the starter solenoid is telling the seat belt system to turn off while cranking ?

need some old timers familiar with this ‘70’s tech

 

According to the manual ( section 86-57) the procedure is:
1.Sit in the car
2. Handbrake on
3. Shifter in N or P
4. Fasten seatbelt
5. If there is a front passenger, fasten their belt
6. Start engine

The wiring diagram I have doesn't show the seatbelt logic module, but the W/Y wire goes from the ignition switch to the starter solenoid/ballast resistor relay.

There are 4 pages devoted to this seatbelt logic module and apparently there was a special Smiths test box to verify the function. It seems like a fairly sophisticated unit. Basically if the transmission is not in N or P and the seatbelt not fastened, the car won't start.

If a seatbelt is unfastened after the car is running there is a warning buzzer and the warning light will come on after a 7.7 second delay.

 

holy ****, you've activated new fears. hahahahhhaahhaahah

 

Looks like you have more wiring to trace anyway.

 

Or, you could just short the seat sensor wires together, I doubt 70s era cars were given enough smarts to know the difference between that and someones rear planted there.
(';')

 

Jagboi is right. The unit is SBM1x (Pektron #) or BLT 5006 (British Leyland Tools. We have one positioned on the east coast and one on the west coast for loan. Here is the east coast one.


Good luck.

 

oh, that's a fascinating machine, thanks for showing that!

Someone before me disconnected the seat sensors, simply unplugged them and the car ran and drive. The seat belt wiring remained original and connected but the car started and ran without seatbelts connected because i test drove it several times with the interior removed. So it seems like someone before me has made some mods.

based on that info from manual, the signal from ignition switch goes through the seat belt control unit and with the starter circuit is interrupted if seat belts are not connected. that wire is white/yellow.

it seems like i could just connected the two white/yellow wires behind dash and be good to go but....

I traced the white yellow wires (there's 2) and one white wire behind dash and checked continuity between dash and the starter relay. I could definitely rule out one white wire and one white/yellow but the remaining white/yellow wire showed about 17 ohms resistance. there was some sort of connected between inside the car and the starter relay on that wire but that seems like too much resistance for a short length of wire and makes think there's something wonky that I don't understand.

thinking maybe ill just cut the bulk of the seat sensor and seat belt wiring and then connect those wires together and reinstall the whole thing as before. unless someone has some other insight

 

The wire with resistance might be powering the warning light bulb. Try pulling the bulb and see what happens..