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speedo Argh HELP
ditchlewis - 29/9/07 at 05:26 PM

Well a good and bad day

i've put the new sensor in to measure the prop shaft bolts.

all works well and the speedo moves in the lower ranges smoothly with out sticking, but above 50 there is some times a jump...

i've got the sensor to with in about 1mm of the bolts and any closer it will be hit by as the bolt turns......

help what do i do????? the SVA is on thursday 8am and i just want to throw the towel in

the speedo is the only thing left to test.

HELP

Ditch


MkIndy7 - 29/9/07 at 05:28 PM

How many magnets is there and how close together?

There could be to many magnets so the signal blurs into one.. above 50mph.

If thats all thats left how can you be considering throwing the towel in! Thursdays ages away!


NeilP - 29/9/07 at 06:10 PM

Ditch,

Mine was a bit jumpy over 40mph but he let me off as it was spot on reading 1mph faster than actual speed.

If it's an occasional hiccup then I wouldn't be too concerned - If it's seriously unstable then that is a fail.

Only locost and quick solution I can offer is this - Get some 5mm think steel plate and cut out some strips, 7mm x 40mm. Bend these over such that they will sit on the outer of the input flange to the diff and then glue on with a metal epoxy resin (making sure than you really roughen up the mating surfaces).

This will then give you a nice strong but more importantly long 12v signal to the speedo when the strip passes under the head - What the speedo is looking for is a square wave input signal and I think that just using the prop shaft bolts makes it too spiky.

Alt no. 2 is to mount the sensor parallel to the chassis rail pointing back towards the propshaft bolts (as you get more metal passing under the sensor head this way).

HTH - Best of....

[Edited on 29/9/2007 by NeilP]


ditchlewis - 29/9/07 at 06:18 PM

there are no magnets the sensor reads the bolts. the heads are aligned with the sensor.

the only thing i can think is that as the bolt turns the edges move closer to the sensor and this confuses it. the jump is only momentary, but this will be a fail i'm sure

ditch


rusty nuts - 29/9/07 at 06:50 PM

My car uses the flange bolts to operate the speedo and does sometimes jump slightly . When it was SVAd the tester made a comment about it saying the best thing to do was make sure the bolts heads are aligned. Might be worth doing ?Don't think they are too worried about jumping as long as it is accurate.


caber - 29/9/07 at 09:42 PM

Hjack alert! do you mount the sensor to the chassis or diff housing for a live axel install? `i am just putting in a new sensor as my first one got chewed by the diss flange!

Caber


mistergrumpy - 29/9/07 at 10:17 PM

Just a thought but could you use cap head bolts to secure the prop to the diff cos then you wouldn't have to orientate them. Them being circular and all.


rusty nuts - 29/9/07 at 10:37 PM

quote:
Originally posted by mistergrumpy
Just a thought but could you use cap head bolts to secure the prop to the diff cos then you wouldn't have to orientate them. Them being circular and all.


Possibly , may be worth a try IF you can get them in the correct thread?


ditchlewis - 30/9/07 at 08:35 AM

many thanks lads, i'm going to put it back on the axel stands and try the speedo out again today

if it's a rare spike i will trymy luck, but if its more then i'm going to make some noise and cut up some steel plate and glue it on.

i will also follow the eldest in his car around the block to check the calibration.

Many thanks
Ditch


martyn_16v - 30/9/07 at 09:24 AM

quote:
Originally posted by caber
Hjack alert! do you mount the sensor to the chassis or diff housing for a live axel install? `i am just putting in a new sensor as my first one got chewed by the diss flange!

Caber


It needs to be mounted so that the clearance between sensor and magnets/bolts is constant, i.e. the sensor moves with the axle.