TVR Tuscan Speedometer issues. Please help!

[richard exley]

My speedometer behaves erratically... Sometimes you can start the car, go for a drive and the speedometer behaves smoothly... Other times it'll bounce around a bit... A few times it has dropped out completely... I replaced the transducer 24 months ago and everything was working I'd get the odd flutter but other than that it was fine when it was replaced.

Now if you're doing 40mph it'll fluctuate anywhere between 20mph and 50mph and occasionally it'll sweep all the way to 190mph and then drop out to 0... Then spring back to life again...

If I really drive hard and hit over a ton, it'll often drop out completely...

I did have a load of dry solder joints on the dash PCB a few months ago, which were causing all sorts of issues, I re soldered them all, and everything is working... Just the bloody speedo causing me trouble intermittently... It'll work well for a couple days sometimes... Then misbehave for weeks...

Any ideas?

Thanks

[richard exley]

My speedometer behaves erratically... Sometimes you can start the car, go for a drive and the speedometer behaves smoothly... Other times it'll bounce around a bit... A few times it has dropped out completely... I replaced the transducer 24 months ago and everything was working I'd get the odd flutter but other than that it was fine when it was replaced.

Now if you're doing 40mph it'll fluctuate anywhere between 20mph and 50mph and occasionally it'll sweep all the way to 190mph and then drop out to 0... Then spring back to life again...

If I really drive hard and hit over a ton, it'll often drop out completely...

I did have a load of dry solder joints on the dash PCB a few months ago, which were causing all sorts of issues, I re soldered them all, and everything is working... Just the bloody speedo causing me trouble intermittently... It'll work well for a couple days sometimes... Then misbehave for weeks...

Any ideas?

Thanks

[carinaman]

You may have more luck in the TVR forum. Link below is for the Tuscan specific sub forum:

https://www.pistonheads.com/gassing/forum.asp?h=0&...

[ColdoRS]

Does the digital readout mirror the analogue? If so, I expect it's the transducer again.

If not, check the plastic on the pod isn't fouling the needle. Also check the needle has been fitted correctly or hasn't moved - does it read higher or lower at 0mph?

[richard exley]

Yeah both the digital and the analog are misbehaving...
Looks like it'll be another bloody sensor... Going to have a quick check of the wiring tomorrow before I bite the bullet and adjust the air gap again, in case it's too close and causing interference.
Cheers for the help

[richard exley]

Sits exactly where it's supposed to at 0

[nawarne]

richard exley said:

Yeah both the digital and the analog are misbehaving...
Looks like it'll be another bloody sensor... Going to have a quick check of the wiring tomorrow before I bite the bullet and adjust the air gap again, in case it's too close and causing interference.
Cheers for the help

Richard, the fact that both digital and analogue outputs are behaving in the same way, indicates to me that it is in the sensor/transducer.

Think folks have mentioned to check the connector in the boot. I'd also add that a silicone spray onto the worm drive for the speedo needle might help?

Nick

[richard exley]

Thanks for the reply, I went ahead and pulled the binnacle open today, re flowed a few more solder joints, and cleaned all terminals with electrical contact cleaner... Speedometer is now working perfectly at the moment.... So may be solved...
However now the bloody digital display is going dim then bright occasionally... I think I've got some dry wires somewhere in behind the binnacle unit in the loom somewhere, so as playing with them then solved this issue and everything seems to be working again...

Bloody cars 😅

[richard exley]

Finally found the fault for anyone that stumbles across this thread...
Went for a drive and speedometer was all working fine...
About minutes in, it began behaving erratically again...
Then the car died completely about 30 minutes after that... Lost all power to all electrics...

The fault:
The main battery earth lead had become degraded, the wires had dried out and began to brake down inside the insulation... This caused the wires to get real hot and the resistance got to such a point, it just couldn't supply enough voltage...

New earth leads routed in, everything works perfectly after a real long drive...

Check your earths people! Don't rush in and buy sensors...
I was real lucky this didn't develop into a nasty fire, especially with how hot the earth lead got!

[nawarne]

richard exley said:

Finally found the fault for anyone that stumbles across this thread...
Went for a drive and speedometer was all working fine...
About minutes in, it began behaving erratically again...
Then the car died completely about 30 minutes after that... Lost all power to all electrics...

The fault:
The main battery earth lead had become degraded, the wires had dried out and began to brake down inside the insulation... This caused the wires to get real hot and the resistance got to such a point, it just couldn't supply enough voltage...

New earth leads routed in, everything works perfectly after a real long drive...

Check your earths people! Don't rush in and buy sensors...
I was real lucky this didn't develop into a nasty fire, especially with how hot the earth lead got!

Good sleuthing there Richard!
Guess you mean the black/earth into the 24-way connector to the binnacle. Or. do you mean the heavy gauge black wire straight off the battery?

Nick

[richard exley]

nawarne said:

Good sleuthing there Richard!
Guess you mean the black/earth into the 24-way connector to the binnacle. Or. do you mean the heavy gauge black wire straight off the battery?

Nick

Main battery earth. The wires inside had become dry and were causing major resistance.