Tach Jumping Issues

Tech chat w/ Marc Matzer
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Marc
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Tach Jumping Issues

Post by Marc » Fri Apr 13, 2007 6:35 pm

If you have issues with your tachometer jumping around or just not working right,add a .68 microfarad capacitor in line on the + side (brown wire going to the tach) to cure this issue.This was a Fiat problem that was addressed with a service memo to the dealers concerning electronic ignitions on 2 litre cars.This might happen on modified cars of any years using an electronic ignition system that is tied into the stock tachometer.

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Denise
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Post by Denise » Sat Apr 14, 2007 5:01 am

Marc, where can I buy this capacitor? The tach on my 71 (electronic ignition) only works when I blow the horn. I get stared at when I feel the need to read the tach! :oops:

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allenlofland
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Post by allenlofland » Sat Apr 14, 2007 9:23 am

But dont confuse this with the tack jumping that could be the warning signs for a mag pick-up cwire self destructing. This tak jump can be the only warning you will get before being stranded by your Electronic Stock Dizzie on the Fiat and Lancias with the mareli unit. 8)
Allen & Lynette Lofland
Wichita Kansas
Back on Land with Our Fiat :)

JohnMontgomery
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TACH Readings

Post by JohnMontgomery » Sun Apr 15, 2007 3:58 pm

I would clean and double check the ground wire cable to the battery and the frame of the car. Also clean the fuse contacts and plug in connectors behind the instrument cluster. I know these are simple things, but seems the tach is very sensitive to grounding and resistance conditions. Not to mention it's cheap to do. Besides, I think those .68 microfarad capacitors are stocked right next to the "Flux Capacitors" in most auto parts stores.
John Montgomery
Greenville, SC
FLU President
2012 Fiat 500 Prima Edizione #77 of 500
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1974 AMC Ambassador
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bran100
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Post by bran100 » Mon Apr 16, 2007 12:59 pm

I had issues with blinkers, tach and other gauges. After a lot of testing and tracing wires, I found that a fuse was "fractured". Not burned, but just a hairline fracture that could only be seen by removing the fuse and 'bending' it to see see the fracture.
Brandon
1982 Fiat Spider
Draper, Utah

kimu
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Joined: Wed Jul 18, 2007 10:08 am

Post by kimu » Wed Jul 18, 2007 10:18 am

Where can one get these glass BUSS fuses? Part number/Vendor please. I have search most parts places and haven't had much luck.

Thanks..

~K

gforaker
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Post by gforaker » Tue Sep 02, 2008 10:12 am

Hmmm,

My 1982 Spider has started reading about 1/3 low on the tach about 10 percent of the time. This intermittent problem just started about 3000 miles ago. Is this a symptom of what you are talking about?

rpconlon
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Post by rpconlon » Tue Sep 02, 2008 3:08 pm

gforaker wrote:Hmmm,

My 1982 Spider has started reading about 1/3 low on the tach about 10 percent of the time. This intermittent problem just started about 3000 miles ago. Is this a symptom of what you are talking about?




I would begin at the grounding pod under the dash over the key. The Magnetic pickup often develops frayed wires and will kill the engine but early symptoms show a very jumpy tachometer and not a low reading one. The pickup should be checked nevertheless. The motor is grounded with cables to the frame and they do break to cause odd electrical stuff as poor grounds are found often through a clutch cable.
It could be a sign of low voltage to the coil which powers the tach. A cheap meter at the coil should show low volts and then you trace backwards.

Cheers
Ron
Ron Conlon
2016 Fiat 500 Sport
Ottawa, Ontario
Canada

Marc
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Electrical Gremlins

Post by Marc » Fri Sep 26, 2008 6:43 am

Many reasons for electrical issues with the tach,all good posts.Leave a post on any problems you may have had with your car and how you fixed it,helpful to all...
Cars are old (old wiring),poor terminal connections,coil issues,bad tach,... etc.
The Fiat bulletin was assuming all else is well,tach still jumping around...I ran into this with a new Dry Coil installed,tach came on at 4000 rpm's to the redline and then didn't work at all in the lower rpm range.

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