speedo sensor

[scott672003]

hi,, speedo,, was jumping about alot, and now sits at zero,, with occasional jump into life, then nothing,, have removed sensor/cleaned and put back on,, nothing at all now,,have read all the old threads and people mention that they need a particular gap set,,, anyone know what that is ??

cheers
scott...

[Big Al.]

Had this on mine a couple of months ago, I was doing 170mph at one stage in a 30 zone.

Sounds very much like the pod will have to come out and go back for repair! Mine fortunately was done under warranty.

[UpTheIron]

Does your digital mph readout also jump around / read 0 mph?

1mm rings a bell for the correct gap, but that could be complete rubbish.

[lady topaz]

Big Al. said:

Had this on mine a couple of months ago, I was doing 170mph at one stage in a 30 zone. Sounds very much like the pod will have to come out and go back for repair! Mine fortunately was done under warranty.

In your case Al you probably were doing 170 in a 30 zone, no change there then!!

Di
xx

[rogerhulks]

Hi Scott, really difficult to say, the sensors tend to be at fault, mine comes and goes, you could get a new sensor and try that first, cheaper than the pod repair. Chat up your local dealer and they may do it FOC. Don't remember anything about a set gap.
Roge

[scott672003]

thanks..
no the digital speedo bit also does not read anything,,,,unless the needle is moving also,,,

the sensor was replaced but that was a couple of years ago.....

there must be a gap to set to,, as there is quite a bit of space between the shaft and the sensor housing

cheers
scott..

[rogerhulks]

bugger ! sounds like time to chat up the dealer, do you have trusted one near you.

[yzf1070]

I have a theory about this unit, but can't prove it at the moment.
The speedo pick up is essentially a proximity sensor. I suspect it is a reed switch type (not inductance type) which typically have an operational life of upto 5 million switch operations. if it is a reed switch type a simple check to prove the device, would be to lift the rear wheels off the ground. Set the gap to 1mm from a tooth and hook up a meter to the sensor. With the sensor on a tooth and the meterr set to ohms find a closed circuit (will be 2 of probably 3 wires). Rotate the road wheels (very slowly) so the toothed wheel switches between a tooth and a gap across the sensor and look for a pulse to open circ on the meter.(Don't rotate the wheel too fast or the meter will not be able to respond fast enough to a change).
Of course if your sensor is goosed this doesn't help prove anything. But if your sensor is ok and it is of the reed switch type its likely your pod is goosed.(Normally I would not suggest such a thing with out first trying it myself as I could be way off the mark but I don't have my car to test this theory as its away on vacation in Salisbury).

Best of luck
Regards
G

[simon t]

Hi
I think its a hall effect sensor, whatever, it runs off the ABS ring on the inner nearside drive shaft CV joint. Its very sensitive to the air gap, if you move it back or forth you may get it working again. Mine speedo was jumping about, moved it closer and it was worse moved it further away and now it's fine

Give it a try

Simon

[J.P]

As the pod readout can be a bit flakey at the best of times - mainly due to sensor input/cables....Is there a possiblility of over-revving the engine (that is if you drive at the limits) i.e if the sensor in charge of the revs is stuffed then how will the car know when to kick the limiter in ?? Or am I being thicko and the limiter is controlled by something more fundamental...

James..

[gudgeon]

i am now on the 3rd sensor the same sort of problems i would get them to change the sensor first as this has cured the problem for a time and the pod i was told could take weeks to months to get back after being fixed. its about time they found a more robust sensor it seems to be a problem, the gap from what i can remember was 30-40 thou about 1mm.

[yzf1070]

simon t said:

Hi I think its a hall effect sensor Simon

Hi Simon
I considered the hall effect principle as that is what is conventionally used for electronic ABS systems. These probes are extremely reliable with their only let down being that iron fillings and rust chips collect around the sensor and interfere with the loop. Often this is the only fault on such like fitted cars when the red light on the dash illuminates. By simply cleaning the debris away normal operation is resumed.

If it is a Hall Effect probe then a small steel screw driver will stick to the probe head. But I discounted this method as they are in my experience such reliable simple semi conductor devices.

Perhaps the sensor is made by TVR as well.....