Donald Sherburn Posted February 25, 2011 Share Posted February 25, 2011 Sons speedometer dial "jumping" all over the place when travelling normally, 30mph reversing out of drive!!!etc etc. Have cleaned up speed sensor electrical connector, no improvement, taken apart & cleaned speed sensor, no improvement, replaced sensor with new part, still no joy. Speedometer instrument removed, needle moving freely with no stickyness at all. Looked at all related items on forum, only thing I found was when renewing sensor no sealing washer supplied so not fitted & "inner" drive to sensor not removed or cleaned as unsure whether it can be removed easily. Can the sensor be checked with multimeter or even hooking sensor up to an electric drill and spinning it?? Looking for answers from you knowledgeable people as I am not willing to "permanently" lend son my hand held GPS!! (He has requested it as an easy fix), thanks in anticipation. Quote Link to comment Share on other sites More sharing options...
DDO173 Posted March 1, 2011 Share Posted March 1, 2011 Sons speedometer dial "jumping" all over the place when travelling normally, 30mph reversing out of drive!!!etc etc. Have cleaned up speed sensor electrical connector, no improvement, taken apart & cleaned speed sensor, no improvement, replaced sensor with new part, still no joy. Speedometer instrument removed, needle moving freely with no stickyness at all. Looked at all related items on forum, only thing I found was when renewing sensor no sealing washer supplied so not fitted & "inner" drive to sensor not removed or cleaned as unsure whether it can be removed easily. Can the sensor be checked with multimeter or even hooking sensor up to an electric drill and spinning it?? Looking for answers from you knowledgeable people as I am not willing to "permanently" lend son my hand held GPS!! (He has requested it as an easy fix), thanks in anticipation. I would suggest jacking a rear wheel up, then with the sensor removed get someone to spin the wheel (transfer box in neutral to reduce drag) then see if the square drive on the rear output housing rotates freely and smoothly. If it does I would then look at the voltage regulator as I have heard this can cause similar symptoms. Quote Link to comment Share on other sites More sharing options...
Donald Sherburn Posted March 2, 2011 Author Share Posted March 2, 2011 Does anyone know if & how the rear output drive can be removed for checking free movement? I intend to carry out futher investigations this weekend as this seems to be the cause. Thanks. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted March 2, 2011 Share Posted March 2, 2011 I thought it was just held in with a single small bolt or screw and then just pulls out but it's a while since I had one out Quote Link to comment Share on other sites More sharing options...
DDO173 Posted March 2, 2011 Share Posted March 2, 2011 Have rebuilt 3 transfer boxes in the last couple of months so its quite fresh in my mind. As BogMonster says the collar that holds the sqaure drive/plastic gear will come out once the transducer is removed by putting a screwdriver under the outer lip and levering it out, the only resistance should be the O-ring but if its been in there a while without being disturbed in may be a bit stiffer with crud build up. It may be possible that if the original transducer had seized in some way it may have restricted the drive member and stripped the plastic teeth (just a hunch). If you want to check the worm drive collar inside the housing, that just unbolts off the back of the transfer box once the prop and handbrake is disconnected. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted March 3, 2011 Share Posted March 3, 2011 The sensor is a magnetic reed switch with a spinning magnet so it closes twice for every revolution. The sensor is driven by a short speedo cable and this could have failed. the sensor is double ended, the big hexagonal nut comes off and you can see the end of the rotor. On a small number of cars there was a mechanical speedo and an electronic speed transducer, typically these were early 14CUx EFi V8 RRC, the 14CUx needs a road speed signal (also handy on police cars with 2 speedos) You can unscrew the existing speedo cable and try spinning the sensor with a hand drill or long narrow screwdriver. Quote Link to comment Share on other sites More sharing options...
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