Lotus Elan

Tacho power issue?

PostPost by: therolfie » Thu Sep 28, 2017 10:12 pm

Hi all, I have a RVI smiths with a Syida circuit inside due to an aldon in the dizzy. Issue will only work when side lights or indicator etc is on? I have tried three different earths, power direct from ignition. Was working fine a while ago, any ideas?
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PostPost by: billwill » Thu Sep 28, 2017 11:40 pm

Though you think not, you must be picking up the power to the tacho from the lighting circuit instead of the ignition circuit.


What wires have you moved recently?
Bill Williams

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PostPost by: alan.barker » Fri Sep 29, 2017 9:36 am

Or maybe the body of the Tacho needs an earth. The earth is fitted to one of the threaded studs holding the Tacho in the dash.
I think the Tacho is back earthing through the light circuit.
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PostPost by: mbell » Fri Sep 29, 2017 6:44 pm

Just had mine out for RVC to RVI conversion...

On my +2 (S130/5) power is via green switched wire and same wire goes on to power supplies alternator warning lamp than earths via alternator. Not sure what car your is and if it has the same wiring but are your warning lamps working.

On mine there are two earth connections, one spade to the rear of the tacho and one wire on the threaded stud.I think the stud one is earth for the full bean light. Does full beam on/off effect the behavior?
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: therolfie » Tue Oct 03, 2017 10:22 pm

I have had an issues posting so testing
Last edited by therolfie on Tue Oct 03, 2017 10:26 pm, edited 1 time in total.
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PostPost by: therolfie » Tue Oct 03, 2017 10:26 pm

Thanks for the replies I have now solved I think, I have found a very old looking green tube connected between voltage stabiliser and the ignition loop wire. It says on it "auto radio fit kit" it could be a suppressor? Old school style? Any way I've taken this out & seems to be working & all other dials are good? Wish I had the knowledge to post pics!

Thanks
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PostPost by: TeeJay » Wed Oct 04, 2017 8:58 am

To upload photos, see the forum Tutorial. The maximum file size used to be 768kb, not sure if this has changed.

Link to Tutorial:- questions-f20/tutorial-how-upload-photos-t27816.html
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PostPost by: therolfie » Wed Oct 04, 2017 5:29 pm

I will look at the pic upload.

Update, well today not working :( Then on the way home when car warm started to work! All good fun.

The plot thickens :D
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PostPost by: therolfie » Tue Oct 10, 2017 7:35 pm

Still will only work when windows are used? So it works as a unit but must be the power somewhere! Will have another look at the weekend :D
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PostPost by: therolfie » Sat Oct 14, 2017 5:38 pm

Ok update, I have removed all other power take offs from the coil e.g. Fuel pump. Still nothing unless a window is used or the fan on full. I have test 12v at the tacho with engine running & have tested signal wire & earth for continuity. I have tried power direct from the battery. I have also tested on the bench & nothing? So will drop the circuit board company an email. Cheers
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PostPost by: EPA » Sat Oct 14, 2017 9:59 pm

This has just rung a bell.
When I fitted new Spiyda card to my tachometer it initially only worked as the engine first started and then returned to zero.
The cure was to put a resistor in series with the signal wire from the coil to reduce the signal produced by the electronic ignition which was overcoming the Spiyda electronics
The electric window load is quite high and may be causing a slight reduction in signal strength causing the tachometer to start working if so you should get the same response if you switch al the lights on etc.
I put an adjustable resistor (100k) in series and adjusted it until the tachometer worked .
Spiyda were very helpful - I think that on later versions a resistor was included along with a filter to stop interference from elsewhere on the car.
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PostPost by: therolfie » Mon Jun 17, 2019 11:58 am

Hi Ed

Forgot to update, thanks for your comments, yes I rung them and they sent me the required parts, fitting in line and all good!

Thanks again
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