Odd tacho issue
Discussion
I have the Smiths RVI 2417/00 rev counter in the Vixen which has always operated fine since I've owned the car. That is until it failed, burning out some internal component & filling the unit with smoke.
So, sent it off to a specialist repairer who suggested upgrading it at the same time to future proof it to run with electronic ignition systems. (It has been running with a basic Accusparc unit just fine but I said 'yes' anyway.)
When I got it back and refitted, it worked fine up to approx 5,000rpm after which it wouldn't rise any more. (this was checked & validated on a rolling road) so it was sent back to the repairer.
They said I needed to have a better quality upgrade to the one they first fitted because the standard unit loses accuracy at the top end. Yes, I know I'm a mug but I paid another £100 and they returned it upgraded for a second time.
Re-fitted it and got a completely different fault in that the needle didn't rise smoothly in line with the revs but did nothing for a second or 2 then would jump to where the engine revs were at. It was now totally un-usable.
Sent it back again and they've checked it on their test rig and say no fault found. They say it must be the car wiring (which seems unlikely as the car hadn't moved for the 2 weeks it was out being repaired) and sent it back to me.
I've now just fitted it back in the car and it's still has the same fault although I've now determined that it is intermittent. I can start the engine and it works fine will even rev to 6,000 rpm now, switch it off then back on again and the jumping fault is back, switch it of then back on and all OK.
Does this (sorry, long and rather tedious) story throw up any ideas from someone more knowledgable as to what might be going on as I'm sitting here scratching my head.
Thx Moto
So, sent it off to a specialist repairer who suggested upgrading it at the same time to future proof it to run with electronic ignition systems. (It has been running with a basic Accusparc unit just fine but I said 'yes' anyway.)
When I got it back and refitted, it worked fine up to approx 5,000rpm after which it wouldn't rise any more. (this was checked & validated on a rolling road) so it was sent back to the repairer.
They said I needed to have a better quality upgrade to the one they first fitted because the standard unit loses accuracy at the top end. Yes, I know I'm a mug but I paid another £100 and they returned it upgraded for a second time.
Re-fitted it and got a completely different fault in that the needle didn't rise smoothly in line with the revs but did nothing for a second or 2 then would jump to where the engine revs were at. It was now totally un-usable.
Sent it back again and they've checked it on their test rig and say no fault found. They say it must be the car wiring (which seems unlikely as the car hadn't moved for the 2 weeks it was out being repaired) and sent it back to me.
I've now just fitted it back in the car and it's still has the same fault although I've now determined that it is intermittent. I can start the engine and it works fine will even rev to 6,000 rpm now, switch it off then back on again and the jumping fault is back, switch it of then back on and all OK.
Does this (sorry, long and rather tedious) story throw up any ideas from someone more knowledgable as to what might be going on as I'm sitting here scratching my head.
Thx Moto
Use your car as a test rig
Disconnect all cables from the tacho, disconnect the coil pos supply that loops through the tacho (well I think it does, I don't think the coil neg will have been used)
Run Twin cable from battery to tacho (that's a pos and neg), connect the neg to the tacho case, connect the pos to one of the loop terminals, run a cable from the other loop terminal to the coil pos terminal
Now make sure that the electronic ignition if fitted is supplied from another cable run from battery pos
Keep things safe, fuse the pos supplies at the battery with 10 to 15 Amp fuses
Most important of all, double check what I've posted so as to be sure all is wired correctly
Now you can keep checking the tacho as and when it takes your fancy, if the tacho plays up you will know it's not a wiring fault
If the coil or electronic ignition were failing and causing the tacho fault there would be one real big misfire
Disconnect all cables from the tacho, disconnect the coil pos supply that loops through the tacho (well I think it does, I don't think the coil neg will have been used)
Run Twin cable from battery to tacho (that's a pos and neg), connect the neg to the tacho case, connect the pos to one of the loop terminals, run a cable from the other loop terminal to the coil pos terminal
Now make sure that the electronic ignition if fitted is supplied from another cable run from battery pos
Keep things safe, fuse the pos supplies at the battery with 10 to 15 Amp fuses
Most important of all, double check what I've posted so as to be sure all is wired correctly
Now you can keep checking the tacho as and when it takes your fancy, if the tacho plays up you will know it's not a wiring fault
If the coil or electronic ignition were failing and causing the tacho fault there would be one real big misfire
I sent mine to Chris at Spyder earlier this year as I had a similar fault plus a jumping needle on turning on ignition. Lumenition here.
I think it was a £50 guts out conversion and works brilliant now.
I would certainly recommend Spyder over SlowWires for speedos, but they did do a good job converting the the ammeter to a volt meter keeping the same face.
I think it was a £50 guts out conversion and works brilliant now.
I would certainly recommend Spyder over SlowWires for speedos, but they did do a good job converting the the ammeter to a volt meter keeping the same face.
Thx for the suggestions on this.
I've now tested the tacho again, plugging into the car wiring I still have the same intermittent fault as above.
Wiring it direct to the battery, coil & earth to by-pass the cars wiring, appeared to resolve the delay / jump fault but lost all calibration with it reading half actual rpm. I guess this means it could be a car wiring issue
Having spoken with the repairer I've now arranged to send it back again (4th time) so they can refit an original Smiths internal unit from the later RVC tacho. They say this 'should' work OK with electronic ignition and resolve the problems. We'll see. ....
The tacho I have is the Smiths RVI 2417/00. It would be good to know if this is what other Vixens are using or if any other models work also. There are a couple on Ebay which are for 4 cylinder -ve earth cars and have an identical face. Just a different unit number and I wonder whether these would be suitable.
Moto
I've now tested the tacho again, plugging into the car wiring I still have the same intermittent fault as above.
Wiring it direct to the battery, coil & earth to by-pass the cars wiring, appeared to resolve the delay / jump fault but lost all calibration with it reading half actual rpm. I guess this means it could be a car wiring issue
Having spoken with the repairer I've now arranged to send it back again (4th time) so they can refit an original Smiths internal unit from the later RVC tacho. They say this 'should' work OK with electronic ignition and resolve the problems. We'll see. ....
The tacho I have is the Smiths RVI 2417/00. It would be good to know if this is what other Vixens are using or if any other models work also. There are a couple on Ebay which are for 4 cylinder -ve earth cars and have an identical face. Just a different unit number and I wonder whether these would be suitable.
Moto
Moto said:
Thx for the suggestions on this.
I've now tested the tacho again, plugging into the car wiring I still have the same intermittent fault as above.
Wiring it direct to the battery, coil & earth to by-pass the cars wiring, appeared to resolve the delay / jump fault but lost all calibration with it reading half actual rpm. I guess this means it could be a car wiring issue
Having spoken with the repairer I've now arranged to send it back again (4th time) so they can refit an original Smiths internal unit from the later RVC tacho. They say this 'should' work OK with electronic ignition and resolve the problems. We'll see. ....
The tacho I have is the Smiths RVI 2417/00. It would be good to know if this is what other Vixens are using or if any other models work also. There are a couple on Ebay which are for 4 cylinder -ve earth cars and have an identical face. Just a different unit number and I wonder whether these would be suitable.
Moto
I can confirm that my Vixen (an S3) has the same tacho.I've now tested the tacho again, plugging into the car wiring I still have the same intermittent fault as above.
Wiring it direct to the battery, coil & earth to by-pass the cars wiring, appeared to resolve the delay / jump fault but lost all calibration with it reading half actual rpm. I guess this means it could be a car wiring issue
Having spoken with the repairer I've now arranged to send it back again (4th time) so they can refit an original Smiths internal unit from the later RVC tacho. They say this 'should' work OK with electronic ignition and resolve the problems. We'll see. ....
The tacho I have is the Smiths RVI 2417/00. It would be good to know if this is what other Vixens are using or if any other models work also. There are a couple on Ebay which are for 4 cylinder -ve earth cars and have an identical face. Just a different unit number and I wonder whether these would be suitable.
Moto
Good luck with your 4th try!!
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