Tachometer / Rev Counter Stopped Working

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David Withers
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Tachometer / Rev Counter Stopped Working

#1 Post by David Withers » Tue Mar 21, 2017 7:26 pm

The tacho on my pre-facelift 2.5 (ex-PI) suddenly stopped working during a short but eagerly driven journey. Not being very hot on electrical systems, I searched our forum for ideas as to the cause and cure, but without great success.

Nothing has been changed that might have affected it, and the ignition is the standard points type, not electronic.

Where should I start to look for the cause?

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Dave B
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Re: Tachometer / Rev Counter Stopped Working

#2 Post by Dave B » Tue Mar 21, 2017 9:24 pm

Sorry to be a bit negative David, but my 2500 pfl did more or less the same last year. It was a bit erratic for a short while, then died completely. A replacement tacho restored the status quo! (which now reminds me, I owe for, dont I John :oops: :oops: )
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David Withers
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Re: Tachometer / Rev Counter Stopped Working

#3 Post by David Withers » Wed Mar 22, 2017 8:41 am

Mine wasn't erratic so far as I'm aware, but I assume the fault is likewise in the instrument itself. I wonder if they are repairable?

It's unfortunate that I gave away my spare PI instrument panel to a member wanting to upgrade his 2000. I hope John hasn't made the same error, but he's almost certainly more sensible than me!

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Re: Tachometer / Rev Counter Stopped Working

#4 Post by Alec » Wed Mar 22, 2017 9:36 am

Hello David,

the first check is the electrical connections on the rear of the instrument, not forgetting the earth.

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Re: Tachometer / Rev Counter Stopped Working

#5 Post by johnnydog » Wed Mar 22, 2017 4:52 pm

Dave B wrote:Sorry to be a bit negative David, but my 2500 pfl did more or less the same last year. It was a bit erratic for a short while, then died completely. A replacement tacho restored the status quo! (which now reminds me, I owe for, dont I John :oops: :oops: )
Just don't leave town..... :lol:

But then again Dave ....... I owe you for the extra muscle when we moved the 'fleet' to their new home!!! :D :D
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Re: Tachometer / Rev Counter Stopped Working

#6 Post by johnnydog » Wed Mar 22, 2017 5:05 pm

David Withers wrote: It's unfortunate that I gave away my spare PI instrument panel to a member wanting to upgrade his 2000. I hope John hasn't made the same error, but he's almost certainly more sensible than me!
No David!
I have a reasonable idea where everything is, what I have, what I can realistically pass on to other Triumph owners, and also I can lay my hands on them when needed. I also am fortunate in the fact that I still have several good used PI speedos in stock!!
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1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red

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Re: Tachometer / Rev Counter Stopped Working

#7 Post by David Withers » Mon Apr 03, 2017 1:57 pm

I've repaired my tachometer for a measly £5.29.

I've written up the procedure for SIXappeal, so won't duplicate it here.

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Re: Tachometer / Rev Counter Stopped Working

#8 Post by Mike Stevens » Mon Apr 03, 2017 3:14 pm

If you've changed some of the electronic bits, the the tacho may need recalibrating. It's not difficult but does need some special (sort of!) equipment. I have the necessary here at home and will, of course, be pleased to calibrate for members if that helps.

I wonder how you checked yours David?

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Re: Tachometer / Rev Counter Stopped Working

#9 Post by David Withers » Tue Apr 04, 2017 7:18 am

Hello Mike.

I calibrated it against 30 and 60 MPH road speeds in third gear, read out from a sat-nav held by my son whilst I watched the tacho (on a straight and quiet country road). Doing it at two road speeds confirmed the consistency.

I thought it best to submit the write-up to SIXappeal rather than to the forum following Kevin's request for more submissions, and it's a bit long for your 'forum extracts' column as well as being illustrated with a photo.

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Re: Tachometer / Rev Counter Stopped Working

#10 Post by Clifford Pope » Tue Apr 04, 2017 9:07 am

This is deviating from the point a bit, but it's interesting that it seems to be universally assumed that Satnav is spot-on for speed.
In my observation that is not true.

My Volvo does an indicated 60mph at 2000 rpm. That may not be the actual speed, but it is consistent. So whatever errors may be present in both devices, they give a reliably correct correlation.
But the Satnav varies in the speed it displays, usually something like 54, but it can be anything from 52 to 58.
It's a basic plug-in Garmin, and very useful. But it would not be a reliable way of calibrating a speedometer or tachometer.

Observations?

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