Where to buy parts - Speed Sensor
Discussion
TVR dealer as the sensor are specific to the speedo and TVR installation. ABout £150 so make sure it is really a duff sensor before parting with your money.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
TVR dealer as the sensor are specific to the speedo and TVR installation. ABout £150 so make sure it is really a duff sensor before parting with your money.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
TVR Power replaced mine (1999 Griff) 2 weeks ago. I didn't pay for it (warranty), but I'm sure they either said it was £62 or £68. I asked Dom at Power whether it was specific to the speedo and he said no.
Sorry - that doesn't help does it - it just confuses the issue!
I haven't had the opportunity to check whether my speedo is reading correctly yet.
Sorry - that doesn't help does it - it just confuses the issue!
I haven't had the opportunity to check whether my speedo is reading correctly yet.
griff2be said: TVR Power replaced mine (1999 Griff) 2 weeks ago. I didn't pay for it (warranty), but I'm sure they either said it was £62 or £68. I asked Dom at Power whether it was specific to the speedo and he said no.
Sorry - that doesn't help does it - it just confuses the issue!
I haven't had the opportunity to check whether my speedo is reading correctly yet.
For a 1999 car not necessarily true but as there are about 11 different instrument suppliers/manufacturer changes I will leave you to make up your own mind especially as getting the wrong type may not generate the correct signal for the ECU or speedo.
PAB said: Thanks for the replies - hopefully one will come good. Will keep you posted. Fortunately I'm not actually usuing it to drive the speedo, only for the ECU input (for idle control) so I make get lucky on matching it easily.
Cheers
PAB
But the same sensor is designed to drive both so I take it you are going to delve into the loom and seperate the two wiring circuits so that the second sensor is independent of the other.
If you want a straightforward sensor from anything then I might suggest that you use a Race Logic traction control sensor. About the best I have come across. The 520 uses 5: 4 for the Tv and a 5th for the speedo.
However and this is a big however, they may or ma not be compatible with the ECU. They require a few MA supply current which the ECU may or may not be able to supply.
If the speedo is working then the ECU faulst is wiring and not sensor and would it not be better to fix the wiring fault than take the risk of blowing up the ECU?
Steve
Mine was replaced because although the speedo was working fine, the ECU was reading fault code 68 (road speed sensor). At low speeds (>5mph) the engine would sometimes stall when I dipped the clutch. Bloody annoying at junctions or in heavy traffic.
I've only done 7 miles since the car came back from TVR Power, so I have no idea if the problem had been cured.
It may yet be a wiring fault.
Isn't there an amplifier in the dash that takes the input from the sensor and amplifies if before it goes to either the speedo or ECU?
I've only done 7 miles since the car came back from TVR Power, so I have no idea if the problem had been cured.
It may yet be a wiring fault.
Isn't there an amplifier in the dash that takes the input from the sensor and amplifies if before it goes to either the speedo or ECU?
Steve might be able to tell you more. There is an amplifier or something behind the dash. I know because i was trying to get a pulse for the sat nav. My speedo doesnt register until 7-8 mph, not good for accuracy crawling in town. I bought an amplifier for such cases and it doesnt work at less than 2mph. Not bad but not perfect. So now i have one that does, so say the supplier. Fitting it today.
The amplifier... I think it is a pulse converter/callibrator for the speedo so that they could use the same speedo with different pick ups and this could explain why it needs a certain speed to register and derive the pulse train.
I suppose it is possible that the sensor was not man enough to drive both the ECU and speedo but it does seem a little strange. Never had a broke set up to play with but have spent hours setting the 520 ones up.
BTW if you want real accurate sat nav, the best thing is to drive a sensor of the front wheels. The rear wheels will often go faster by upto 10% under power so the speedo reading you see is often slightly higher than the actual front. The 520 has its traction control set to this to get the maximum grip but it means on the data logging, the two rear wheels show up going 8-10% faster.
Steve
www.tvrbooks.co.uk
I suppose it is possible that the sensor was not man enough to drive both the ECU and speedo but it does seem a little strange. Never had a broke set up to play with but have spent hours setting the 520 ones up.
BTW if you want real accurate sat nav, the best thing is to drive a sensor of the front wheels. The rear wheels will often go faster by upto 10% under power so the speedo reading you see is often slightly higher than the actual front. The 520 has its traction control set to this to get the maximum grip but it means on the data logging, the two rear wheels show up going 8-10% faster.
Steve
www.tvrbooks.co.uk
Actually i had thought of the front but thought the steering slowing the wheel down on bends and things was a stumbling block. However if the rears are 10% out under "power" then maybe the fronts are not so out, or are they? I personally do not find a problem with the 2 mph cut off point but somebody who i know, IS.
My speedo packs up on the odd occasion; all appears to be well at the connections at the back end by diff. Does anyone know what happens wiring/amplifier wise from the speedo, working backwards? I have no idling/running problems so assume ECU side of things must be ok. Hopefully the speedo is ok, have not noticed if digital odometer packs up at the same time, it does not pack up long enough to check it (hope that continues) but would like to get it working all the time. Anyone know exactly how this speedo/odometer works? 
The speedo containe an electro-mechnaimcal counter that counts pulses generated by the sensor as the transmission turns. These signals drive the speedo (stepper motor or incudction drive to the needle) and the odometer is a speperate counter. Unless you have access to a scope and know how to fault find electronic equipment don't even think of probing any of this stuff as it can blow the circuits and even the ECU.
About 5 pages on the theory and a fault diagnosis chart is in the new bible. All covers printed, proofs signed off and delivery is next week.
Steve
About 5 pages on the theory and a fault diagnosis chart is in the new bible. All covers printed, proofs signed off and delivery is next week.
Steve
Have had cars before with this kind of speedo setup but none of them affected the running of the car. I understand how the stepper side of things works but have heard people mention an amplifier behind the dash. Does this "amplifier" exist, if so where is it, is it controlled by the ECU or by the sensor on the diff?
Ivan
Ivan
Errr go back a few posts. It is a pulse converter that changes the pulse train so the speedo is calibrated with the signals it receives. Not all cars have them. The ECU uses the road speed signal to determine what the hell is going on and whthere you have lifted off or simple want to idle. Without it it gets confused and does all the wrong things.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
shpub said: Errr go back a few posts. It is a pulse converter that changes the pulse train so the speedo is calibrated with the signals it receives. Not all cars have them. The ECU uses the road speed signal to determine what the hell is going on and whthere you have lifted off or simple want to idle. Without it it gets confused and does all the wrong things.
Steve
Ok the 3mph cut off point is simple enough, that is in place to stop the ECU having conflicting signals, no problem with that. Have read all the posts but none answering the question. You are saying that some cars do not have the amplifiers, fair enough. What pulses the speedo if that is the case?
Ivan
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