erratic speedo.
Author
Discussion

clive f

Original Poster:

7,259 posts

254 months

Sunday 21st July 2013
quotequote all
the sag developed a strange problem today, once car was warmed up, well hot actually in this weather, I noticed when on tickover that the speedo flickers up and down on the needle on the clock, and the digital readout goes from 12mph to 250mph throwing a bit of a hissy fit, once you start moving the speedo settles down to record the actual speed no problem.

got off the ferry coming home this evening, speedo again throwing a fit on tickover, and found when I dropped my son home that you then cannot open the doors as the funny speedo reading is telling the ecu that the car must be moving so hence it wont let you out!

anyone had this experience, the car must be female to throw a few toys out of the pram like thishehe

Ant.

5,254 posts

302 months

Monday 22nd July 2013
quotequote all
Is it charging ok?
I know it seems unrelated, but when my speedo started acting funny soon after the battery went flat I found the 100a fuse by the alt had corroded connections, all ok since I sorted it.
If it's not that , then maybe there is crud on the sensor?

If the interior buttons don't let you open the door anytime, I wind the window down and hit the mirror button.

clive f

Original Poster:

7,259 posts

254 months

Monday 22nd July 2013
quotequote all
hi Ant, charging is fine, however I was running with aircon and fan on full blast yesterday, so perhaps this has drained the battery? charging not sufficient when this is on drawing a lot of juice?

will check fuse by alternator, however that was new last year and coated in grease.
opening doors can easily be solved but obviously tied in to this fault as the car thinks its moving.

Whitenoise1

197 posts

160 months

Monday 22nd July 2013
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The tolerances for the speedo sensor are minute. It has to be very close to work properly. You can see it from the left rear wheel arch. Could be that this has moved. Try readjusting to see if it fixes it. Could just be a duff sensor if you are getting strange readings.

Andy

jonesy

333 posts

305 months

Monday 22nd July 2013
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it will probably be the sensor. I've had 3 go, its fairly common, check the clearance or renew.

J.

clive f

Original Poster:

7,259 posts

254 months

Monday 22nd July 2013
quotequote all
wondering if the aircon is causing the faulting readings on tickover? it does get very cold in the dashboard when the aircon is on.

if it is the sensor, would it not show a faulty reading all the time? when the car is moving there is no problem whatsoever.

jonesy

333 posts

305 months

Tuesday 23rd July 2013
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when mine failed it would give random results, from reading 250 when stationary to flicking from actual speed to 180 on the move.

J.

Luckey

345 posts

231 months

Thursday 25th July 2013
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Hi

I've recently observed the same randomness but only whilst moving. One day all would be fine but then randomness would return .... then all ok again.......
Finally, I observed that the running battery voltage dropped a little and the erratic jumps became more pronounced. Car ended up with my local independent who diagnosed a failure of the alternator voltage regulator. All fuses were OK when checked first.

Car is back with me now and all has been fine since ...... paranoi dictates that I keep looking for randomness.


Edited by Luckey on Thursday 25th July 07:31