Tacho Not Working

Talk about the E-Type Series 3
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IFC123
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#1 Tacho Not Working

Post by IFC123 » Wed Mar 31, 2021 8:31 pm

1971 V12 LHD
Hi everyone,
I imported my car from the US a few years ago as a non runner.
Fortunately for me, it was only a detached lead to the starter motor & it started straight away.
Since then I've been refurbishing it but very slowly!
The latest problem is the tacho is not working (no movement of the needle at all) it's never worked under my ownership.
I've removed the tacho from the dash, uncoupled it and reconnected it.
Is there a way of checking whether it is receiving a signal from the ballast resistor or anything obvious to check, before I send the unit away for investigation?
Electrics is not a strong point so as simple an explanation as possible please.
Can anyone recommend a suitable repairer, if possible in South Yorks area?

Many thanks
Ian

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christopher storey
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#2 Re: Tacho Not Working

Post by christopher storey » Wed Mar 31, 2021 9:10 pm

Ian : the electronic tachos require two electrical sources to operate . No 1 is the impulse signal from the distributor/coil to the tacho . No 2 is the continuous - while the ignition is switched on - supply ( usually a green wire ) from one of the fuses to the moving coil which drives the needle . It is also very important that the tacho case is properly earthed and this usually requires a black wire from one of the fastening down studs of the tacho to the binnacle case, and also ensuring that the binnacle case itself is properly earthed to the chassis. You need a voltmeter/continuity tester to carry out checks properly - these are readily available at modest cost

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#3 Re: Tacho Not Working

Post by IFC123 » Wed Mar 31, 2021 9:47 pm

Thanks Christopher,
I do have a multimeter and can use it to check continuity.
I am positive that there was no earth from the binnacle case to the fastening studs.
How is the binnacle case usually earthed to the chassis? the only thing connected to mine was the 4 pin plug connecting the wires you mentioned.
I will have a look again on Friday, armed with this information.

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#4 Re: Tacho Not Working

Post by christopher storey » Thu Apr 01, 2021 9:06 am

The binnacle should be earthed by the fastenings to the bulkhead, but it often happens over the years that the earths break down through dirt/corrosion , and this is why I would suggest establishing a good earth to the tacho case itself as a first step. Similarly, cleaning the plug in connector terminals with e.g. switch cleaner is worth trying

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#5 Re: Tacho Not Working

Post by IFC123 » Fri Apr 02, 2021 6:18 pm

So, as recommended by Christopher I cleaned the 4 pin connector & the connection to the ballast resistor, checked continuity which was fine & cleaned the clamp connections to the bulkhead.
Then ran a new earth from the binnacle case to the bulkhead.
Unfortunately it's still not working, so I guess it's time to have the tacho checked/repaired.
Can anyone recommend a suitable repairer?

Thanks Ian

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#6 Re: Tacho Not Working

Post by christopher storey » Sat Apr 03, 2021 9:49 am

I have used Speedograph Richfield 0115 926 4235 for a number of instruments, with great satisfaction. Whether they are right for an electronic tacho, I don't know, but it is worthwhile ringing them to see, and they are not too far away from you in Nottingham

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#7 Re: Tacho Not Working

Post by IFC123 » Sat Apr 03, 2021 2:41 pm

Thanks Christopher,
I'll give them a go

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Rui
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#8 Re: Tacho Not Working

Post by Rui » Sun Apr 18, 2021 2:34 pm

It may well be the tachometer. In case it is, the tachometer has a Integrated Circuit from Texas Instruments which is not produced any longer and it may breakdown.
I retrofitted the tachometer with a device you can get from spiyda.com, in the UK,, attached to the back of the case and it has been working since then.
Easy , inexpensive and hassle-free fix.

good luck
Rui

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#9 Re: Tacho Not Working

Post by IFC123 » Sun Apr 18, 2021 6:54 pm

Thanks Rui,
I sent the tacho last week to Speedograph Richfield, should be back next week, so I'll report back.

regards
Ian

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