4x5x5

Suspect has new Voltage reg last month. Meter showing barely 12V even though Alt putting out 14V and battery showing 14 when engine running. Any BTDT on a flakey Volt meter?
Mike

boxerfan

If the needle isn't jumping around then I'd suspect that it was factory calibrated poorly... i.e. it met spec for consumer display purposes... but that is a bit of a long shot.

You might want to examine your wiring diagram and see where the meter pulls it's level from. A corroded connector could cause that much drop if it is getting hot. You are losing 2V and you definitely want mA rather than A acting parasitically. 2V across 1kOhm gives 1mA. 2V across 1Ohm gives 1Amp... that's what will get hot.

RussB

At heart, every analog meter measures current. Within the case of a voltmeter, a precise resistor is in series with the meter movement and the scale is calibrated in Volts. Good Voltmeters will use movements of substantially less than one milliAmp (for full scale deflection) -- maybe 50 microAmps. (I have no idea what yours is.)

The meter will read low if there's ANY undesired series resistance. (Most cars will have relatively crude meter movements that draw more current than lab instruments do. This makes them cheap and rugged; it also makes them susceptible to inaccuarcy that's caused by undesired external resistances.) I'd suspect a bad connection somewhere in the instrument cluster's meter circuit -- either on its "+" (positive) side or its "-" (negative) side.

Oxidation in the meter circuit may be the cause of a low voltage reading. After cleaning both halves of a connection, before asembly, I like to use Ideal NoAlOx goop to prevent future oxidation.

I've read that the 100 and 200 are prone to instrument cluster electrical problems with the printed circuits, apparently suffering from hairline cracks in the current traces. I'd look there.

I doubt that the resistor within the meter or the movement itself could have drifted that far -- but anything's possible. The only way to confirm that the meter's okay is to connect a known voltage source directly to its terminals and see what voltage it reads.<ul><li><a href="http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/volmet.html">http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/volmet.html</a</li></ul>

onebrokenneck

Mine does that intermittently. It will read 8-10 volts and today it was reading 15-16 volts at idle. Sometimes when I start the car, the needle will not move for a bit and then will react later almost like it is stuck or something. Anyone have a solution other than replacing the gauge?