98 Z3 2.8 Roadster
- Thread starter StephenK
- Start date
- Joined
- Dec 8, 2011
- Points
- 145
Just a quick one on the probable reason why everything stopped when the brake was pressed. It's the same reason for how the alternator warning light works on the dashboard...
12v to one side of the motor makes it work, as there is a 12v difference across the motor.
12v to both sides of the motor stops the motor, as the difference across the motor is 0v.
In the case of the alternator warning light...
12v from battery through bulb and through non-charging alternator to earth = bulb illuminated (12v across the bulb)
12v from battery through bulb and 12v generated by alternator = bulb extinguished (0v across the bulb)
When something stops if 12v is applied, it's usually caused by this effect.
12v to one side of the motor makes it work, as there is a 12v difference across the motor.
12v to both sides of the motor stops the motor, as the difference across the motor is 0v.
In the case of the alternator warning light...
12v from battery through bulb and through non-charging alternator to earth = bulb illuminated (12v across the bulb)
12v from battery through bulb and 12v generated by alternator = bulb extinguished (0v across the bulb)
When something stops if 12v is applied, it's usually caused by this effect.
Thank you. This totally makes sense.
I really appreciate your input on this. Fingers crossed there is no other underlying cause for the wire having been cut and spurious feed applied.
to the forum from me too in Stafford. Sounds like you've sorted out your roof
There will be a video on the roof shenanigans as I got a reasonable amount of footage of seat and carpet removal to route wiring front to rear, even though I didn’t need to, thanks to my ‘pilot error’. In actuality, it wasn’t in vain because I also ran the new wire from instrument housing to diff speed sensor as someone had run that outside of the vehicle. All part of the journey so best to include it, warts and all as it’s not all puppy dogs and kittens 