Talk Morgan Forums Thread Like Summary - 1998 +4 4 Seater - Speedo

Hi all,

I wonder if anyone can help with an issue I am having with the speedo in my 1998 +4.

The speedo occasionaly reads the right speed but more often than not it is swinging wildly around from 0 - 100 mph.
I have had the speedo sent to Speedy Cables who have bench tested it several times and confirm it it working correctly and have replace the inners one one occasion but it still does not show the right speed all of the time, when it does it appears to be quite accurate when compared to my GPS speedo that I have to have in the car.

Do anyone have any idea what I can check next to see if I can resolve the issue?

Thanks

Laurie

Hi Laurie

There is a component connected between pin 8 (sensor signal in) and pin 3 (earth) on the plug that fits into the back of my instrument. Unfortunately I don't know what it is because it is contained within a piece of sleeving. It could well be a resistor and if that is the case it would be a 'pull down' resistor but this depends upon the type of sensor fitted. My sensor is fitted in the vehicle's gearbox, I suspect your sensor is near the front wheel hub and they may be different electrically. I have not heard of failures of this component.

I followed the cable from my sensor and it arrives at a three pin connector, hanging in the cables on the drivers side (see photo). The steering column shaft is just under my hand. The three pins carry earth, plus 12 volts with the ignition on and the third pin is the signal back from the sensor. I jacked one of the rear wheels up, monitored the voltage on the signal pin with a volt meter, got my wife to spin the rear wheel and watched the signal volts changing from high to low as the wheel rotated. You might be able to do a similar test if you can find your sensor connector but in your case it will probably be one of the front wheels. Obviously the ignition needs to be on during this test.

I have posted the details of the VDO speedo test rig within another post, see here

https://www.talkmorgan.com/ubbthrea...er-not-working-on-2008-plus-4#Post817814