toothed wheel - what is it for?

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timb2117
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toothed wheel - what is it for?

Hello, this is the rear inside driver side of 05 K series SV. The toothed wheel has a sensor with black wire attached. Am I way off in guessing it feeds in to the ECU for road speed measurement? - I know from sad experience that the speedo is driven from gearbox......Thanks for looking. Tim

Jonathan Kay
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Does it match anything in the Speedometer Guide?

Jonathan

Eccles
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Hi Tim,

You are correct in your guessing. Mine, a 2007 Sigma, uses that for the speedo and the gearbox hole is plugged up. Yours could be a mixture of bits as they changed over systems maybe?

Ivan

2007 S3 Sigma 150

timb2117
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Thanks Jonathan that's the sucker, although cant for the life of me think why they fitted it then ran the speedo direct off gearbox....

Reason I'm asking is I have effectively cactussed the gearbox feed and have just grabbed a new speedo from caerbont which is the later programmable type- and wouldn't it be so simple to use this feed?

However without tracing the wires all the way back up the car its pretty well impossible to tell where it goes or what it is feeding in its current format.

Could well be the case Ivan - I wonder if the builder fitted it "coz its in the box" then ran out of use for the signal :) so I will have a bit of a look as far as I can, couldn't be any more tucked away though, groan.

ScottR400D
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Couldn't you just put new wiring in to run the speedo from the sensor? 

Jonathan Kay
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"Reason I'm asking is I have effectively cactussed the gearbox feed and have just grabbed a new speedo from caerbont which is the later programmable type- and wouldn't it be so simple to use this feed?

"However without tracing the wires all the way back up the car its pretty well impossible to tell where it goes or what it is feeding in its current format."

That shouldn't be too hard with a diagram, the wiring colours, a multimeter and a car sized length of cable. But one of those signal injectors would also help.

Or rewire as above.

There would also be the issue of which signal and sense the sender and speedometer use. But there are some very clever and helpful people there who could design a converter if there isn't one available off the shelf...

Jonathan

timb2117
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Thankyou you good people - yup I can fairly easily run the wires and the great guys at caerbont are including a sender specific to their speedo,

Scott I am a bit loathed to pinch the signal from the existing sender if it is (long shot) doing something useful like feeding the ecu....I will have as good a look as possible at where its wires go to.

Worst case (given the less is more philosophy of our cars) I will fit the new caerbont sender in tandem with the existing one and wire it fresh to the new speedo.   

ScottR400D
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Apologies. I missed the bit where there's already a sender in place. It would be good to know what that's doing. 

 

Jonathan Kay
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Great: you've got a plan and you've got a fallback plan.  : - )

I'd test the new sender and speedo as soon as you've got both, and probably with a quick rig before you do a lot of fitting.

Jonathan

John Vine
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I'm puzzled why you would have two senders.  Some questions:

Is your existing gearbox-mounted sender one of these?

What's the history of the car? 

Does the driveshaft sender have 12v supply?

Does the LED light up as you rotate the toothed (reluctor) ring?  (My guess would be that this sender does nothing speedo-wise at the moment, so it may well be suitable as-is for your new speedo, providing you have the necessary wiring at the speedo end.)

What speedo do you have at the moment?  Can you post up a photo of the back, with Caerbont and CC part numbers?  And does it have a switch block under the black grommet?  If so, how many switches?

What model is your new speedo (Caerbont/CC numbers)?


These threads may help to shed light: here and here.

JV

Beagler
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Is it not for ABS. Those driveshafts will be for other tin tops.

2019 270S 1.6