When the LED reads open both ways, but lights ?

[petemoore]

  Easy Vibe's power supply
  V+ 9.5v
  10k
  Vbias 7.6v
  LED
  LED
  1n914
  Gnd. 0.0v
  The meter doesn't read the foreward voltage [or reverse] but the LED's lite up when I put test by putting current through just the LED's.
  I was expecting the recommended 3.8volts at vbias, and pulled the divider string/battery clip and rechecked but still the meter reads 7.6v at Vbias.
  The meter and the circuit have fresh alkalines, 9.4+ volts.

[R.G.]

What color LEDs did you use? LEDs vary a lot in forward voltage.

[amptramp]

Some meters have a low test voltage that will not be enough to light an LED.  If you have a test voltage of 1.5 volts (popular on some of the cheaper and older meters), you can't get a reading on anything but an infrared LED which has a forward drop of about 1.1 volts.  These are used in optoisolators, so you do run into them in pedal builds.  The last time I used a red LED as a voltage reference, it measured 1.88 volts.  As the wavelength of the colour gets shorter, the voltage gets higher.  Yellows may run around 2.2, greens around 2.5 and blues over 3 volts.  Most meters try to use a low voltage since some parts may only be rated for low voltages.