Speedo sensor not returning to zero

[Toady1]

Hi, I've got my S off the road atm as weather and roads are so ste and tax ran out in Jan, so decided to do a few fixes to it. Today I took the clocks apart to fix the perspe screen back into place as it had been pushed back into the needle. I've put it all back, turned the ignition switch on and the speedo needle dropped down to about -20mph position. Also every time I start the car now I get ECU fault code A poping up. Will this cure itslef once I take it out for a drive or do I need to take it all apart again and make sure its back together properly? Thanks in advance if anyone knows! It's currently SORN'd so I can't really drive to it check if it re-calibrates itself or not!

[S6 Devil]

I recently had fault code A come up and the speedo needle was stuck at 40 mph. I was told that it was either:

1. The micro-switch under the gold plate has failed OR
2. Check the gearbox assembly on the dash for problems, is the needle boss firmly attached to the shaft?

Mine was the second option and easily fixed without taking the speedo apart. I managed to access the boss and shaft through one of the side flaps and pushed it back together. Job done!

[JimmyZZ]

I recommend to check the simplest cause first: does the needle touch the surface of the speedo plate?
Common reason after disassemly because you might have bent the needle a little bit during repair, easy fix!

Edited by JimmyZZ on Sunday 3rd March 05:58

[Toady1]

I didn't tuch the needle or the gearbox when stripping it down, the perspex is pushed back (forwards) into place and isn't touching the needle. The needle was in the 0mph position until I turned the ignition on, then it moved to about -20mph and hasn't moved back to 0 since. I moved the car forward and back to see if the needle moved as the speed of the car went up and it did, but this was only on my drive so couldn't go too far or fast enough to see what it was, I just know it moved. I guess I'll have to strip it down again to double check everything.

[S6 Devil]

When I pushed the boss and shaft back together and started the car, my needle dropped to the bottom. On turning it off and then starting it up again and driving it, all returned to normal. Might be worth driving up and down the drive/road/round the block first.

Edited by S6 Devil on Sunday 3rd March 23:43

[Toady1]

Yep I might just leave it for now and see what it does when I get it back on the road! Diff bushes to do next! Yay!!!

[Toady1]

well I've stripped it all back down again and put it back together and no change. The needle was all attached to the gearbox fine and I couldn't move it that way. fault code A still comes up on the pod and its still reading about -20 to -30mph lower than the digi display, any ideas people?

[S6 Devil]

Sounds like either the micro-switch under the gold plate has failed or the stepper motor. I sent mine to Cath Mason when I first got the car. All tested and repaired for £150

[Toady1]

Annoyingly tho it was working before I took it apart so I might give it another go stripping it incase it's a loose connection.

[Toady1]

I don't suppose u know or have a picture of the sensor?

[S6 Devil]

Toady1 said:

I don't suppose u know or have a picture of the sensor?

Alas no!

[geoffphead]

My Tam did this when I stripped dash etc,mine went back to normal after 6-7 start stops and resets.Make sure you really push home all the dash ribbon leads.
The other thing i had was some see thru plastic discs that were lose in behind the pod screen and were jamming speedo needle.

[Toady1]

Thanks Geoff, though the tuscan is quite different to the tamora clocks, I just remembered I did move the gold speedo back whilst it was all apart to get to the perspex to push it back in to place, so maybe I've dislodged something there. I'll check that again tomorrow.

[Toady1]

Update:- I may have found the problem, in fact I'm convinced I have, just not put them back in yet to confirm it. I stripped the clocks down again yesterday and found the wire that goes to the speedo needle switch had been trapped/rubbing against the ally dash to the point where the insulation had worn down. So it must have been shorting out on it. This makes sense as to why the needle dropped to -20mph when the ignition was turned on.

I also found a wire on the right hand ribbon to be broken, just need to find my soldering iron now to fix that! That will be why the led's weren't working on the display switch!



The pictures were with my iPhone I'm afraid so not the best!

But hope these posts may help out others in the future. I'll repost when I'ce put it all back in.

Edited by Toady1 on Tuesday 9th April 10:46

[Walford]

Do you know which pin out is for the speedo signal

[Toady1]

No I don't I'm afraid, a wiring diagram would be great eh!!