Speed sensor

[Robbo D]

Hi guys. I think I need a new speed sensor. I have had the old one off and cleaned everything up and refitted with a slightly smaller are gap 0.8 thou but still the Speedo dosent start to work until around 20-30 mph then works fine until I stop then the cycle starts again. I’m sure I saw someone one here was selling a compatible sensor at sensible money. Please advise.

Rob

[Adrian@]

Amazon ...Msp6724 here is the link. https://www.pistonheads.com/gassing/topic.asp?h=0&...
A@

Edited by Adrian@ on Wednesday 16th September 18:02

[Robbo D]

Yes seen that. Any further updates on how this is working out. The other thing is they all seem to be coming from china so worth be delivered for a couple of weeks

Rob

[Adrian@]

Here goes, it even has the plug on (I bought a sensor way back, for the spares box, as I have two cars running it, and ordered the plugs that cost me more than the sensor)!
https://motaclan.com/product/speedo-transducer_tvr...

[BritishTvr450]

It’s long since been known that often the Speedo doesn’t register until around 20 mph, so don’t be surprised if a new one makes no difference.

[Robbo D]

Ha ha £16 or £150 so just purchased the Chinese version. Hopefully be here next week so will report back when it’s fitted.

Rob

[Robbo D]

BritishTvr450 said:

It s long since been known that often the Speedo doesn t register until around 20 mph, so don t be surprised if a new one makes no difference.

Can’t recall the car doing this when I got the car so think this is a recent problem. I did notice on Sunday the car was slow to drop to idle when coming to a stop again a recent thing.

Rob

[sixor8]

My last Chimaera and my current Griff both do this, nothing till about 20 mph and then drops to zero once you go under 20 mph again.

[Loubaruch]

You can easily check the speed sensor on the bench.

Connect it to a digital voltmeter on the lowest DC voltage range and just flick a steel object close to the sensor you should notice a very small deflection.

No deflection indicates a duff sensor any deflection its OK.

[PabloGee]

My speedo didn't really register below 20mph.
It would also show around 3-5mph faster than the speed my mobile phone satnav would read - most notable at motorway speeds, as though the degree of inaccuracy increases the faster the car is travelling.
Not that I know which of those would be the correct reference of course.

I recently took my diff out, and when I refitting I moved the speed sensor a little closer to the toothed wheel - but still not 8 thou, more like 12-15 thou.
I have the GKN diff, so the wheel is on the front of the diff at the point the prop shaft attaches.
What I also realised is that not all the teeth were straight (it's actually a fairly soft metal), so I spent a bit of time with a set square and a vice tweaking the teeth to be consistent.

All of this made two differences - the speedo picked up at more like 10-15mph, and the speed reads closer to 1-3mph faster than the mobile phone satnav above 70mph.