Is there any VDO experts out there!!!
I have a VDO electronic speedo that will not read above 40mph.It is all wired correctly with the sender picking up on the driveshaft bolt heads on the diff. flange.According to the instructions the speedo can be calibrated using a known value of pulses/mile which i have worked out and entered into the speedo,but it will only read upto 40mph( which is wrong considering i have had it sat on axle doing 12000 rpm in 6th!)
Has anybody used the VDO speedo and had the same problems?

You don't pick up from the driveshaft bolt heads. You should have got a magnetic sender which should be mounted to the wheel or something similar. 1 rev of the wheel = 1 rev of the magnet.

The circumference of the diameter is then entered into the headset (readout). For an outside tyre diameter of a 15" wheel and tyre combination (481mm diameter) the reading you enter into the headset should be the circumference around the tyre which would approximately be 1511mm.

If you're still having problems it sounds like the unit you have will only read upto 40mph. You need a Cytec C10 which accurately reads up to 120+ guaranteed with a certificate which the SVA man will like to see.

Hope this helps.

[Edited on 21-8-04 by Hellfire]

Cheers mate,i will try mounting a magnet on the drive shaft. I throught the sender would have picked up from the bolt heads as it is magnetic,but seems it is not strong enough to get a pulse when the bolts as spining around above 40mph!

i had same problem using 4 magnets on the prop. speedo got only to 50mph; phone ceabont the manufacturers who said the pickup is not sensing the gaps between the magnet at high speed, so try using only 1 or 2 magnets instead- that fixed it for me.

I've got a VDO speedo on my Westfield and it picks up from the driveshaft bolt heads.

The key is to get it within 1-3 mm of the heads.

The gap on mine is about 1.5 mm and it works fine.

Cheers
Simon