Speedo no-go!

[Grin-a-lot]

Speedo is wired correctly but when I plug the inductive sender in it automatically reads approximate 20mph when stationary.  When I attempt to calibrate it, I can't seem to get it to respond properly and the speed is all over the place.  I'm using an inductive sender and have stuck 2 magnets to the prop shaft to send a signal.

Is the magnet/sender set up a reasonable way of doing it or should I look at something else?  Is there a way of testing/proving the sender or gauge?

I'm at bit of a loss as to what to look for next!

['The Gaffer']

Is this any good? http://www.gomog.com/allmorgan/VDOCALIBRATION.html

[Grin-a-lot]

'fraid not!  Been through the calibration but continues to act weird.  It measures a pulse, attempts a sweep of the dial (goes a bit nuts during it) and then doesn't seem to respond to revs.

I've been spinning the wheels on stands on the driveway.

I've got the sender pointing radially at the magnets which are mounted on a coupling face so facing in the axial direction.  Would it be  better to have the sender facing axially as well or perhaps have 2magnets mounted on the prop shaft with the sender looking directly at them radially?

Perhaps I've not given it the best signal that I could have...

['The Gaffer']

Just a thought, are the polarity of the magnets correct, facing the right way?

Dont think it matters where they are as long as they are 180 degrees apart and you have the correct air gap to the sensor.

[Grin-a-lot]

Not thought about polarity to be honest!  I'll have a look when I jack the car up again.  They are 180 deg apart though and close to sender.  Thought I'd check the wiring is good and clean the face of the sender as well.  The bouncing around made me think it's receiving a signal and thefact it was reading a speed when the car was out of gear is hopefully a calibration issue so no big deal.

[mr tone]

How did you sort  your speedo in the end,having problems myself with diff and speedo Tony

[Mike the Bike]

I had trouble with a Vapor digital speedo on my car. I mounted the magnet to the side of the propshaft and the speedo worked
great up to 46mph and then went heywire everytime.
Moved the magnet to a front brake disc mounting bolt head and now the speedo is working perfectly.

[Grin-a-lot]

Speedo not currently sorted really, beginning to look like a faulty sender.  Any ideas what the resistance of a VDO inductive sender is or any other ways I can check it's "health"?

The gauge still sits at 20mph most of the time, responds ocassionally and drops to zero intermittently.

Investigations ongoing!

[Jonkoxe]

Hi,

Not sure if you have this fixed yet but I thought these instructions might help.......
http://www.greengauges.com/help/faq18.asp