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Discussion Starter #1
Seems like I'm full of questions today. The electronic tachometer on my 91 Spider has never worked since I bought the car two years ago. I'm trying to start with the disconnected or corroded wire concept before I rip the instrument cluster apart. My wiring diagrams have not helped me find the trigger wire going to the cluster. One older posting on this site said a white or green wire coming off the coil, but the CD shop manual talks about a flywheel sensor. Any ideas on where to start looking?

Thanks again,

John

1991 Alfa spider
 

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On your 91 the tach signal is coming from the coil.
Have you tried giving the tach a good dope slap? Mine periodically stops working, a good smack and it works fine again!
 

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Discussion Starter #3
I can see already that one of the invaluable assets of this forum is the wealth of technical expertise and highly-detailed engineering analysis. With deep respect for that empirical approach, I decided to take Paradiso's advise and give my inert rev counter a "good smack." Why not, all my other efforts have failed. Sitting in the driveway on a cold Sunday in February, revving the engine, I whack the instrument cluster and see the tach needle bounce. Well, that looked promising. Smack it again and, lo and behold, I have a rev counter again! Holy moly! That puppy hasn't moved in two years.

Thanks very much for the, ahem, practical advice, Paradiso. I owe you one.

John

1991 Spider
 

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Discussion Starter #4
No, Murray, I did not. I did find your suggestion helpful and I did locate that extensive thread about calibrating both the speedo and the tach. This summer I anticipate pulling quite a bit of the interior apart for a general restoration and I think I will do calibrations at that time if needed.

Thanks for your help,

John
 

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My pleasure. Always happy to share my wealth of highly technical knowledge. You should see what I can fix with a baby sledge! :D
 

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Ye My 92 also like slap also it works on fuel gauge both of them like a slap

Ha
 

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Discussion Starter #8
Update on tachometer:

Out for a short spin in the 91 Spider yesterday in the New England cold and while watching my tachometer, I see it fall from 2500 RPM to the stop pin and just quit. Gave it more "whacks" while driving and it did come back.

To me that raises the issue that the tachometer doesn't get "stuck", but rather is loosing its electrical connection. I suspect minute amounts of corrosion building up on the connectors behind the instrument cluster is the culprit. I do plan to remove the cluster when the weather warms and will disconnect/clean/re-seat those connectors several times. Can anyone confirm that this line of thinking is correct? I've already pulled all the fuses and cleaned them with WD-40 and my brass-bristled brush. I still have several other non-functioning electrical items.
 

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instead of wd40 I will suggest to use Contact Cleaner...
 

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Yep, contact cleaner, or even better Caig DeOxit. WD40 is not good for electrical connections - you want them clean, not oily.

Also make sure you check out John's thread where he shows the potentially loose solder joints on the tach pins.

http://www.alfabb.com/bb/forums/showthread.php?t=2902
 
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