bouncy tach and no start

[Sirius Driver]

My 1982 euro is acting up. I noticed that once in a while my tach will start bouncing around. It will go to ZERO if I turn on my lights or if depress the brakes. The other weird part is that it the car will not start whenever the tach starts to bounce around. Ive left it alone for over 8 hours and no start. It will start if I push start it, and a Jump start does nothing. I have plenty of battery juice, It could be a ground but where do I start? Or has anyone have this happened to em?

[KNS]

When you say battery has "plenty of Juice" how much are we taliking? You should have 12.8 to 13 volts. It might start with less volts if everything else is tip-top.

[mca]

Voltage regulator going bad will trigger tach to bounce.

[Joe Bob]

When it bounces....see if you can get a voltmeter on the circuit. Even if it one of those cheap assplugin models.....if you see a spike in output, it's the VR.

[Targalid]

I found this little gizmo handy for diagnosing my charging system. You plug it into the cigarette lighter and you can see the voltage fluctuations while driving. My voltage would spike above 15 volts to as high as 17 volts. I replaced the voltage regulator when I saw this. Helped fix the bouncing tach.
http://www.amazon.com/Vector-VEC008-Digital-Voltmeter-Volt/dp/B0002ISEQW

[Sirius Driver]

Drove the car all weekend and couldnt get it to act up. Is the VR internal or External in an '82'?

[timmy2]

If it is external you will have this on the drivers side. Black box connected to the silver box (regulator) below in center of picture.

[djbrand1]

I thought an external regulator was just piggy backed on the alternator itself?

[Joe Bob]

It does on a VW....

[adamr]

Sorry to hi-jack the thread but in the pic of ignition system, the very top fuse is for what? Mine is missing and dont know what that fuse is?
Sorry again


Adam

[Sirius Driver]

I think those fuses are for your blower motor/heater and such. Okay, I'll look when I get home. I hope its external.

[timmy2]

2 fuses for engine heater blower circuit, one for targa rear window defroster on my car.

[djbrand1]

The top fuse is for the rear window wiper, if you have one.

[Gustyones]

Joe Bob, nice avatar. Reminds me of the old band Bananarama...