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Overdrive inhibitor sensor

Inhibits engaging overdrive if too slow a gear wheel or in this case broken wires to the sensor. Looks as though transmission fluid makes the wiring sleeving go hard and brittle then vibration completes the job. No I don't know what its from , built into a 3/8 UNF stud though so localises it a bit I suppose . Is the system passive or active.? Magnet as a pole piece inside a coil probably, 330 ohm, 60nH. Spinning a steel cog in a drill , passive output is about 10mV sineish pk-pk 5mm from gear and about 100mV if 3mm from the gear. But also a lot of EMI from the drill motor so are these things used actively ?

Reply to
N_Cook
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From what make and model vehicle? And yes, they are active, feeding an amplifier and pulse shaper to provide a final RPM value to the TCM.

Reply to
Peter2

don't

output

I was not told what its from. Googling I only found references to overdrive inhibitor switches not tachometer type sensors. So a standing 12V across them ?

Reply to
N_Cook

I think you should ask this question in uk.rec.cars.maintenance instead. Lots of very knowledgeable people there.

Gareth.

Reply to
Gareth Magennis

Your description is an inductive tachometer pickup coil... I don't think you will find any biased with 12 volts across them either.

Reply to
Peter2

you

I hope gearboxes make good Faraday screens against ignition EMI, there is no braid screening around the signal wires though.

Reply to
N_Cook

Generally twisted pair is used (at least on the ones that I work with), and I've had little problems with EMI (though I do work primarily with diesel trucks so EMI won't be ignition based at least). These same transmission (for me) are used with gas engines however, so it appears to the designer that EMI won't be an issue.

Reply to
Peter2

Used in a Land Rover

Reply to
N_Cook

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