I have a 740 automatic estate(wagon ?)in the UK. The Haynes manual says that the sender unit is mounted on the back axle. This sender unit sends pulses to the electronic speedometer.
How does this sender unit work? Are there magnets in the axle inducing pulses in a coil on the sender unit? Or is it an optical unit reading rotations of gear teeth? Or some other method?
Secondly, Where does the cruise control get its pulses from? The Haynes manual says from the back of the speedometer. Does anyone know the correct connection?
I have a kit cruise control that has been on the last 5 cars, various makes, all manual gear change. The pulses were taken from the ignition coil. I had it on my last 740 which had manual gearstick. The ignition coil pulse cannot be used on an automatic. Instead the kit has magnets which are strapped around the prop shaft, together with a pickup coil. I was wondering whether I could use the speedo connection mentioned above, instead of crawling under the car etc.
Many thanks guys for your help.