My headlights-on voltage is around +11V. The sense line for night dimming is listed at +12V to activate. Night dimming does not work for me. Am I right to suspect that the voltage is not quite high enough to activate the sensor?

At some point, I am probably going to wire something up to work around this (opto-coupler gating constant-power to headlight sense wire, controlled by car's headlight voltage), but in the mean time, can anyone confirm/refute this interpretation of the problem?