Tachometer problem

[Dads77spider]

1977 124 California version (just in case that may matter)
Tack jumps immediately at start and goes up to 4000 RPM, shakes a bit and stays between 3500 and 4200 RPM.
Checked coil wire, re attached the capacitor (condenser) looked behind the dash 'board' wire seem to be attached.

Is there a way to test the tach itself?
Anyone had this problem/ know of a solution?

[WYSpider]

bump

[Dads77spider]

bump

Anyone know about the Tachometer, Tach problems?
Why it goes up to 4k RPMs and hovers?
What should I check ?

[124JOE]

the wire on the - side of the coil goes to the tach
my bro has a tester that has rpm so he tests rpm on the coil

you may have a bad wire.as your tach does move

[Dads77spider]

The coil wire is correct, and not the problem that I can tell. Power comes from it.

I read on another post about a wire shorting a plug or sensor on the Transmission causing a similar problem, so I looked under there and found a broken plug that has a loose wire, but connecting it had little or no effect ( a slight move of the needle).

P1050215Trans-plugb by jonnyracerx, on Flickr

[spider2081]

That looks like your back up light switch. There should be 2 wires on it. One has voltage on it and the other goes to the back up lights. The switch closes when you put the car in reverse and turns on the back-up lights

If you disconnect the tach wire from the coil does the tach still display the 2-4000 rpm ??? If it does I would think the tach itself might be defective.

Do you have points in distributor or is it solid state?? If you have points are they in good shape and is the capacitor known to be good.

[124JOE]

one wire on the coil goes to the pluss side thats power in
the other wire gose to the tach it reads resistance,if it has a short MORE RESISTANCE.joe

[Dads77spider]

That looks like your back up light switch. There should be 2 wires on it. One has voltage on it and the other goes to the back up lights. The switch closes when you put the car in reverse and turns on the back-up lights
If you disconnect the tach wire from the coil does the tach still display the 2-4000 rpm ??? If it does I would think the tach itself might be defective.
Do you have points in distributor or is it solid state?? If you have points are they in good shape and is the capacitor known to be good.

Could be back-up, but I'm pretty sure it has 3 or 4 wires, and 1 is busted off. I'll try to jack it up more to get a better pic.

I'm pretty sure the tach reads 0 when the wire to coil is unhooked, but I'll try it again tomorrow.

Distributor has 2 sets of points, I don't know how good the capacitors are. How do I test them (without burning up my multi-meter)?

BTW, Joe, a short-circuit has too little resistance, that's why the wires can burn (wires have resistance, longer = more).
http://en.wikipedia.org/wiki/Short_circuit

[Dads77spider]

Ok got a better pic:

[Dads77spider]

Ok, got it cleaned off.
the blue wire goes to 2 contacts, and the red is the one disconnected, But the reverse lights work fine.

my alternate tach is a speedometer...

[Dads77spider]

Ok, got it cleaned off.
the blue wire goes to 2 contacts, and the red is the one disconnected, But the reverse lights work fine.
my alternate tach is a speedometer...

Bump*

-- Anyone know if these wires have anything to do with tach problems, Or what they do go to?

[4uall]

I am sure you may already have this however, this may help if you do not

http://www.artigue.com/fiatcontent/Wiring_1977.pdf

http://www.fiatspiderparts.com/trouble.html