My Multimeter goes crazy when I try to test my voltage....

If I touch it to the battery (in the back of the car) it will jump around from 0 to 19.xx to 15.xx to 17.xx to 7.xx etcetc.
Weird enough but...

If up in the engine bay as soon as I move the mulitmeter into the bay itself (without being hooked up to anything) it does the same thing!!! Its like its getting interference via air transmitted waves. As soon as I move it back over the fender outside the car it goes to 0.00 and stays there.

I was thinking voltage regulator but since its doing this without being hooked up to anything I'm totally clueless.

Can anyone venture a guess

 

Have you verified this with a second meter just to make sure the first isn't flaking out? If so, there may be an alternator diode problem, although this would only happen with the engine running.

 

Yea two multimeters seem to do this. It only does it when the car is running and its done this with two alternators.

I have a battery hooked up to the car still could this make a difference? When the car is off and the charger is still on it reads a solid 13.7 at the battery and 13.6 at the distroblock in the bay and the alternator.

 

It might be worthwhile to split open the alternator, expose the rectifier assembly, and test all six diodes.

 

I can do that. How does one test a diode?

 

it will be an open circuit one way and a closed circuit the other (one way wil have no resistance (or very little.)

 

The other consideration is that if you are using an autoranging meter, it may be displaying a mV reading generated by the leads being exposed to EM near power sources. Try locking the meter onto a 20V or similarly appropriate scale, or use an analog voltmeter. (I despise those auto-range only meters.)

 

I'm using the 20v selection on both meters. As far as I know there isn't autorange fuction on mine.