Change from gearbox speed sensor to wheel speed sensor-k series

[Albert Donaldson]

Wondered if anybody had changed from gearbox speedo sensor to a wheel/propshaft speed sensor on a k-series and if so what was involved.

thanks.

[Geoff Brown]

Could be technically challenging & expensive.

You would require as a minimum (at a guess):

Serrated sensor wheel for offside drive shaft or if not possible complete new offside drive shaft.

Mounting bracket.

Sensor with loom + loom to instrument cluster. New/recon speedometer acceptable for sensor input.

 

[John Vine]

Agree about the driveshaft.

Some other thoughts...

As your speedo already translates sensor pulses, it could be that it would work with a new sensor.  I guess it would depend on the characteristics of the sensor signal.  You'd need to check with Caerbont.

Connecting the new sensor to the existing loom could pose problems.  Your sensor is 2-wire,  The new sensor is 3-wire, as it includes a live 12v supply to power the (Hall Effect) sensor.  So, you'll need to lay in a new 12v supply.  You'd need to check with Caerbont whether the new signal would be compatible with your speedo. . 

What year is your car?

JV

[Richard Price]

I've done it on a 2006 car, where the speed drive gear had moved on the output shaft  

It is a 2006 car and has the Caterham branded a fully programmable speedo (which I think were introduced somewhere 05/06).

I made a bracket to hold a proximity detector to sense propshaft to diff flange bolts. The standard electronic sender uses just a 12v supply, and a switch wire back to the speedo. The proximity detector that I used also needed a 0v so I connected directly to the chassis.

[Graham Howard]

I have just done this and It is not that difficult. Richard Price set me along this path.

First you have to establish if you have a post 2005 speedo where you can set the number of pulses per mile. To check this hold the  odometer button in while you turn on the ignition. You should see a number displayed which is the number of pulses per mile. After 3 seconds the leftmost digit will start flashing. If this happens you have a speedo where you can set the pulses per mile.

The instructions here will apply to calibrate the speedo for the new sensor.

Then I used a proximity sensor which picks up from the front brake disc bolts, so the speedo will see 4 pulses for every revolution of the wheel. You will need to make a bracket to fit to the steering arm bolt.

This is the sensor I used.

The sensor has 3 wires: Sensor black connects to blue/red on the car (signal), sensor brown connects to green on tha car (+ve) and sensor blue needs to be earthed somewhere on the chassis. The sensor has flashing LED's to show that it is functioning and the gap is correct to the disc bolts.

The reason I did this was to remove the gearbox sensor which always leaked oil.

 

[Graham Howard]

Just beat me to it Richard!

[John Vine]

Very neat bracket!  What is it attached to?

 

First you have to establish if you have a post 2005 speedo where you can set the number of pulses per mile. To check this hold the  odometer button in while you turn on the ignition. You should see a number displayed which is the number of pulses per mile.

Can you not do the same thing with the earlier speedo (pre-2004? -- which the OP may have) by means of the 10 switches at the back?

JV

[Richard Price]

John,

'not sure what era has 10 switches?

My own car (2002) has just four switches, but actually only has two settings.

[Richard Price]

Graham  

[Northantsbedsbucks AR]

The bracket is made from a washer bottle bracket which I had surplus. It is mounted between the steering arm and the upright replacing the washer in that position. 

There is another document on the Caerbont website which describes setting pulses with dip switch setting but I don't know if this type of speedo was ever used by Caterham. 

[Albert Donaldson]

Thank-you very much gentlemen, it is a 2007 metric chassis K-series. I believe speedo is compatible. I am going to try picking up on the propshaft with an led inductive speed sensor from merlin and try to utilise the original piece of harness, if this fails it will be the front wheel, as the toothed driveshaft is not fitted.

Albert 

[John Vine]

'not sure what era has 10 switches?

No, nor am I.  I raised the possibility only because the Caerbont website suggests that it might be a precursor to the current programmable speedo (with the 6-digit code).

JV

 

[John Vine]

it is a 2007 metric chassis K-series. I believe speedo is compatible

When you press and hold the trip reset button and then turn on the ignition, is a 6-digit code displayed?  If so, what is the value?

JV

[Albert Donaldson]

It displays 008786.

[John Vine]

Thanks for that.  Good to have a value on record for the benefit of others.  There's loads of pulse/mile information for the driveshaft sensor (see this Guide), but very little on the gearbox-driven one.

(02Nov22: Edited to fix 404 link.)

JV

[timb2117]

Exactly as Richard and Graham have said, and not a difficult job, Caerbont massively helpful as I was 2005, and had to ge tthe later speedo that was compatible so '07 should be fine.

Only slight furphy for me was when a heavily fresh tarred and stone chipped road allowed a stone to knock the sensor out = dead speedo, then when I moved it back in (too much) it picked up 2x pulses per bolt, so apparently I can do about 200mph just spinning wheel with my hand :)

Its a great home project, good luck.