VDO Speedometer and ETB sensor

[Quinten]

This may be one for @Welly Jen, but I'm not seeing any movement on my VDO speedometer now I've changed the sensor (from gearbox to wheel sensor).  The VDO gauge is the standard Westfield supplied one which has 8 terminals on the back.  The (inductive?) sensor from ETB has 3 wires: power / ground / signal.  I connected the signal wire to terminal 8 as per diagram 3 as that seems the closest match.

But as said, I'm not seeing a signal.  How should it be wired up?

[Kit Car Electronics]

An ETB 3 wire sensor is a powered Hall effect one, so diagram 1 should apply...

[Quinten]

Cheers @Kit Car Electronics, just to confirm then, the ETB sensor has 3 wires

blue = ground to pin 3 (I have this currently to another ground point, would it matter if I left it?)
brown = 12V to pin 2 (I assume that pin 2 is 12V, so if I have this to a separate 12V, would it matter if I left it?)
black = signal to pin 6 and 8

 

[Kit Car Electronics]

You might need ETB to confirm the colours of the sensor. Google thinks the VDO Pin 2 is 12V - check with a multimeter - if so, you can use the separate 12V you already have. 

[Quinten]

Thanks again Mike, ETB helpfully included a little piece of paper identifying the colours, and they are as above.  I think the bridge with pin 6 is the missing link.  Not allowed to go anywhere near my car today, so will give that a go tomorrow 

[Kit Car Electronics]

7 minutes ago, Quinten Uijldert - Northants AO said:

Thanks again Mike, ETB helpfully included a little piece of paper identifying the colours, and they are as above.  I think the bridge with pin 6 is the missing link.  Not allowed to go anywhere near my car today, so will give that a go tomorrow 

yes, the bridge is to a pin that has a pull-up resistor attached to it inside the speedo

[Quinten]

Alas, bridging 6 and 8 together and leaving power/ground separate has not made any difference.  Will have to try feeding the sensor from the gauge, but if that doesn't work I am a bit at a loss.  I did check the wheel sensor and it lights up yellow when the bolts pass.

[fossett]

I did the same job, but had no speedo,

So as an additional step I glued rare earth magnets to my front hub bolts (where the sensor picks up in my case).

It has worked fine ever since!

 

[Quinten]

I've spoken to ETB who confirmed that I should only need to connect to terminal 8 for this sensor and that power/ground can come from another source than the terminals on the gauge.  They did (rightfully) remind me to check the configuration of the gauge, as the default number of pulses is something ridiculously high that you'd have to drive at 300+ mph for it to register on the gauge.  So I checked it when home and yes, the number of pulses was set to 16260 (I have no idea why!) so I changed it to the more appropriate value of 3550 (4 bolts on 185/60R14 tyres = 3548 according to http://awooga.nl/stuff/vdo.html).  This time the odometer is at least increasing, but the needle does not move much.  I've still got the bridge in place (as to remove it I need to remove scuttle again, not a quick 5 min job), so I will remove that tomorrow and try again.

I still need to ensure the gap is 2mm on all bolts, but quite how I am going to be able to check that is still the case when driving, I'm not sure...  Maybe mount a camera near it and see if it sees the led?

[Kit Car Electronics]

hmm. So the ETB hall sensor must already have the pull-up fitted internally. In which case, the bridge to Pin 6 wouldn't be needed, but I can't think why it would actually be a problem when it is fitted. You should be able to spin the wheel to 10mph easily by hand - does that read reliably? If you had an oscilloscope you could check you have a good signal at the speedo. Obviously make sure the speedo and sensor grounds are good, too.

[Quinten]

I don't know what it was that fixed it, but after removing the link to 6 and ensuring the sensor itself was definitely picking up the bolts, even when the bracket flexes a little bit it all worked 

Now I just need to verify that 70 == 70, as 100 came up rather quick this time  

Cheers Mike!

[mattstone79]

Sorry to resurrect an old thread but I am also having some issues with the same setup as above. Although my issue is slightly different, when the sensor is over a bolt the speedo shows a constant 70mph until the wheel is turned and the sensor moves off the bolt, the speedo then drops to zero. The sensor lights up yellow when over a bolt.

Playing with the pulse settings just changes the speed that shows on the speedo when the sensor is over a bolt.

I've probably done something stupid but all appears to be wired up correctly, (Signal wired to pin 8)

Anybody have any ideas?