Speedo Issue

[TVRHEAVEN]

Hi all, I took my Chimaera into a garage who after looking at my speedo told me it was the transponder. They have replaced it with a new one but now the speed doesn't register until the car is nearly at 20mph!! Does anyone know why this is the case?? Cheers

[mgaut]

sounds like you need to take it back to the garage and get them to advise ?

Mike

[S4CJO]

Check the gap between the transponder and the toothed wheel on the diff. You'll need to check "The Bible", unless someone else pickups up this thread, for the correct distance.

Mine did exactly the same so I adjusted it to approx 3mm clearance. Don't go to tight or the toothed wheel will destroy the end of the transponder.

Or as Mr Gaut pointed out..........take it back.

[Flintstone]

S4CJO said:

Mine did exactly the same so I adjusted it to approx 3mm clearance. Don't go to tight or the toothed wheel will destroy the end of the transponder.

Make sure you turn the wheel and check clearance on each tooth. If you set it based on one tooth and others are closer, ouch.

[The Dodger]

S4CJO said:

Check the gap between the transponder and the toothed wheel on the diff. You'll need to check "The Bible", unless someone else pickups up this thread, for the correct distance.

Mine did exactly the same so I adjusted it to approx 3mm clearance. Don't go to tight or the toothed wheel will destroy the end of the transponder.

Or as Mr Gaut pointed out..........take it back.

It needs to be MUCH closer than that - I can't find the figure at the moment but I'm sure it was a fraction of 1mm. Try a search for it. Or, just get it as close as poss without touching?

[TVRHEAVEN]

Thanks very much everyone

[V8 Animal]

6 thou IIRC

[peteA]

Just out of interest...how do you get to the road speed sensor to adjust it...?

Cleaned mine up recently with a spray and air gun but cant see how you would get to it from under the car...?

Do you gain access from inside via the rear of the transmission tunnel?

[spend]

Early cars with the sensor at the front of the diff, are not so easy to access You really need to drop the exhaust & propshaft, to loosen the locknut you may have to take the sensor bracket off the front of the diff. In comparison to the later 'abs' ring style the early set up is far less demanding concerning the gap required, and rarely requires any adjustment at all (it just works ).

Dave

[edward1]

Some one could actually supply a transponder! I was told reacently from a local Indie that they were currently impossible to source. I am living with a speedo that doesn't wake up until 35/40. Had a look at the clearance and tried cleaning the end, any closer and the toothed wheel would destroy it.

Access from the underside on a '98 isn't too bad as things TVR go!

[chimalsu]

changed my transponder last year set to 6-7 thou and doesnt start reading until 20mph but then bang on accurate at all speeds compared with sat nav,so quite happy to leave as it is,since this happened ive looked at my 944 speedo and that does the same

[sparkythecat]

edward1 said:

Some one could actually supply a transponder! I was told reacently from a local Indie that they were currently impossible to source. I am living with a speedo that doesn't wake up until 35/40. Had a look at the clearance and tried cleaning the end, any closer and the toothed wheel would destroy it.

Access from the underside on a '98 isn't too bad as things TVR go!

You need to gap the sensor using a feeler guage. It's no good just guessing.
As others have said the gap should be around six thousandths of an inch