Hi I have a VW Polo ,2001yr, and the rev needle is not working as it should, when you turn the key it does not zero its self and then when the engine is working it works but the needle is well below where it should be, I dont really mind but its kinda anoying if you know what I mean.
2001 VW Polo Rev clock working but not as it should be.
- Thread starter wilki
- Start date
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I would think you would need to ask an auto electrician for a definative answer, I only speak from past expierence with a Escort td, alternator failed, rev counter would not work correctly.
Wotan
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M
Mickymoody
If the gauge doesn't centre itself, then the earth is faulty, or the gauge itself is faulty.
Rev counter pickup is traditionally from the coil, not the alterator. So a faulty coil could cause a fault.
Rev counter pickup is traditionally from the coil, not the alterator. So a faulty coil could cause a fault.
A lot of cars pick up engine revs from the alternator. The engine speed device for the emissions tester in my M.O.T station clips on to the battery exactly for this purpose.
M
Mickymoody
Well - obviously a diesel car wouldn't have a coil...so the signal couldn't be picked up from it. So 'traditionally', as cars are petrol powered, they have coils, and 'traditionally' the rpm is collected from that.
On a more modern car the rpm is picked up from the ECU.
The older petrol cars yes, sensed from the coil, known as an impulse tachometer, but even then there were exceptions, jaguars had a tacho generator driven off the end of one of the camshafts.There were also mechanically driven tachos driven by flexible cable, as per speedo.
Wotan
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