Can low voltage make the tach jump? RESOLVED

[ga.spyder]

I am getting my 82 back on the road after a lengthy repair.I took a test drive and she ran great, But..... My alternator light came on .It has been coming on when I first start until I rev it a bit,then it was fine.Now it is staying on.I tested it,and it isnt putting out much.I have a new one on the way.The tach is also acting up.It seems normal at idle,but as soon as you give it any throttle,it goes haywire.Jumping all over the place.Can this be caused by low voltage,or is there a shared wire between the alt and tach that could cause both issues?
Craig

[GDR76SPIDER]

Is the belt tension maybe too loose? Maybe that's why when u rev it, it may catch kinda thing?

As for the tach, check ur connection at the coil, could possibly be the issue?

[joelbert2k]

I starting having tach bounce issues when the wires on the electronic ignition pickup became old, frayed and brittle. (not unlike me )

Joel

[FiatMac]

Craig,
Have you seen the article on Mirafiori FAQ pages? http://www.mirafiori.com/faq/content/ta ... achfix.htm

[TX82FIAT]

I have seen voltage and electrical irregularities effect the tac. The 82 alternator has an internal voltage regulator. If your electical systems are in good working order and it does come down to the alternator you may want to consider the 95 amp alternator. If you do not want the 95 amp alternator. I have a working original 65A alternator that i took out of my 82' that I would sell. i've been holding on to it for over a year in case there are any issues with the 95 amp alternator. Over a year and 5000 miles later the alternator is functioning fine so i can get rid of the backup.

I replaced the alternator at the same time i installed the headlight relay. It's a joy to have a fiat with bright lights, fast wipers and a loud radio.

[spider2081]

There is always the possibility of a loose connection. The output of the alternator has 2 black wires the larger goes to the starter solenoid terminal with the green battery and brown ignition switch wire. Behind the alternator there are 2 single wire terminals one has red wires the other has brown wires. I would check this terminal as it is below the fuel rail. From that terminal the brown wire goes through the firewall to C17 the brown wire junction behind instrument panel. From C17 it continues to C31 the ignition switch connector. when the ignition switch is in "start or Run" the blue/red wire at C31 feeds the alternator out light. The small black wire at the alternator output goes through the firewall to fuse 10. Fuse 10 is jumped to fuse 9 the black wire on the unfused side of fuse 9 continues to C31 the ignition switch connector. With the switch in "run or start" the pink wires at C31 feed the ignition and power the tac. I think C31 the ignition switch plug is the most common point to both your problems.
Have you checked the tac connection at the coil???

[ga.spyder]

It gets curiouser and curiouser!! I had a 65 amp alt. that I bought from Autozone 3 years ago.Lifetime warranty which they honored.Before removing the old one I stuck a voltmeter to the back,grounded on the case and the frame.I was getting extremely high readings..up to 17 volts Ah-ha thinks I,internal reg. is fried.Hopped on my Harley ,ran to the zone brought home my new one .Installed it and,same result.WTH?? Alt light is glowing tach is jumping.Try to get a reading on voltage and the car dies.And...it wont restart.I notice when I turn my key to 'ON',the battery icon lights but not the oil symbol.It always has before.And when the key is on,my clock stops ticking and the fuel pump doesnt energize and run.I hope somebody has an idea.I do...but I cant buy C-4!!!!!!

[ga.spyder]

Thanks for all the input.I now have a new alternator that I didnt need I had a couple of bad connections at the alternator and the wires going back to the dash.Car is idling and revving smoothly,no glowing charge light and no jumpy tach.I need to replace a couple ring terminals,grease all connections,etc..These are all a result of having my catchers mitt hands in there taking the fuel rail in and out!!Now,on to relacing fuel lines and the tank.I have my winter projects lined up. Special thanks to my friends Ron and David.You guys are probably sorry you gave me your phone numbers

[rlux4]

No way buddy! Your call gave me an excuse to get away from that customer who wanted to talk about everything he "might" do instead of what he actually wants me to do! What was causing the fuel pump to not run?
Ron

[ga.spyder]

Ron,I dont know! Those wires apparently go into the ignition switch.When I found the issue worked out,I didnt ivestigate any further. I am a firm believer in leaving well enough alone!!! Thanks again,Buddy.Its always nice to get to trade stories over the phone with you.

[rlux4]

Oh yeah. I agree.
Also, you're spared the hassle of locating the inline fuse until a later date!
Ron

[ga.spyder]

Hey Ron,while I was poking around inside the car to figure on routing and removing hard lines.I stumbled on the dreaded inline fuse.It was in fine shape,so I gingerly put it back!!