series 3 bouncing rev counter

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Peter Walvin
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Joined: Fri Apr 02, 2021 4:33 pm
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#1 series 3 bouncing rev counter

Post by Peter Walvin » Fri Apr 02, 2021 4:40 pm

Hello to all,
I have a series 3 FHC which has an annoying problem- the rev counter bounces not reading out the correct revs.

The engine is fitted with an Opus ignition conversion kit from SNG Barratt- don't know if this may be faulty or I need a new one.

Has anyone else got/had a similar issue and can guide me.

Many thanks in advance

Peter

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MarekH
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#2 Re: series 3 bouncing rev counter

Post by MarekH » Sat Apr 03, 2021 8:16 am

Rather than saying it bounces, are you saying it records zero and returns to the correct value periodically? If so, it is likely something is not making a good electrical connection and that includes the earthing of the tacho itself.

If you think it is SNGB related, then ask them how their tacho signal differs from that of the OPUS.

kind regards
Marek

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Peter Walvin
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#3 Re: series 3 bouncing rev counter

Post by Peter Walvin » Sat Apr 03, 2021 8:57 am

Thanks Marek,

By bouncing I mean on tick over it goes up and down and the same when driving along- not a stable reading, fluctuates over 1000-1500 revs.

Regards

Peter

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MarekH
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#4 Re: series 3 bouncing rev counter

Post by MarekH » Sat Apr 03, 2021 10:25 am

Then it probably isn't a complete loss of connection, but an inconsistent input. I'd get (or borrow) another tacho of the same type on ebay for a few pounds (even a six cylinder one or xjs item will do) and check to see whether it behaves the same way. If it does, then the problem is upstream and not the tacho itself.

It may that you have a partially failing connection or component somewhere. You ought to diagnose and describe it better: -wavering but always being capped at the correct reading is different from wavering above and below the correct reading. "Correct" is probably something you know at idle when fully warmed up - it'd be hard to estimate correct rpm above idle speed.

kind regards
Marek

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Peter Walvin
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#5 Re: series 3 bouncing rev counter

Post by Peter Walvin » Sun Apr 04, 2021 9:13 am

Thanks again Marek- appreciated.

I will look into your suggestion with a lot of help from my mechanic.

Cheers

Peter

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Topic author
Peter Walvin
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#6 Re: series 3 bouncing rev counter

Post by Peter Walvin » Sun Jun 27, 2021 9:17 am

Problem now solved thanks to the advice from Peter at SNG Barratt - had fitted a 10k ohm resister- good to see a steady rev counter. :smile:

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