XJ6 & XJ12 Series I, II & III 1968-1992

Speedometer Test? Gauge or sensor?

 
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Old 09-21-2014, 11:18 PM
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Default Speedometer Test? Gauge or sensor?

Hey there...

Just bought this car 2 weeks ago. Speedometer stopped working on the drive home. When I was searching the net trying to find out how to test the actual problem, it mysteriously started working again! Only to have stopped and started multiple times in the past few days. Does anyone know if a way to test it and see what the cause is??

Thank you in advance for any help!!
 
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Old 09-22-2014, 12:11 AM
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Check the connections at the back of the speedo. If they're clean and tight then the problem is likely the speedometer transducer on the transmission. Common culprit.

Your cruise control and trip computer use signals from the transducer as well. If all 3 act up at the same time it even more strongly points to the transducer.

Cheers
DD
 
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Old 09-22-2014, 01:14 AM
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Is it easy to get to the back of the gauge? I haven't tried the cruise control, I've had a bad experience in the past and shy away from this luxury feature. However, when the speedometer stops, the mileage stops counting. (Understandably so...) When you say trip computer, do you mean the unit in the center that has the average MPG, etc?

Thanks so much for your help!
 
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Old 09-22-2014, 07:14 AM
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Originally Posted by SouthernGal View Post
Is it easy to get to the back of the gauge?

Remove the under-dash panel and you can reach the speedo easily.

From slightly foggy memory....

Remove one screw from the end cap at the extreme end of the dash. This will expose two screws screws holding the under-dash panel. Now look for one or two more screws roughly where the under-dash panel meets the console.



When you say trip computer, do you mean the unit in the center that has the average MPG, etc?

Yes.

Set it on 'average speed'. If the display goes wonky at the same time the speedometer goes wonky, it more strongly points to the transducer being at fault

Cheers
DD
 
 
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