The wiring diagram in the 914 installation manual shows TCU harness pins 28 and 10 going to the warning lamp, and 11 and 35 going to the caution lamp, but does not indicate the polarity, I have LED indicators, so I have to know the polarity to wire them. Does anyone know which pins are positive and which are negative?
  • Re: TCU warning lamp polarity

    by » 6 years ago

    Aviator 79
    The Maintenance Manual 76-00-00 page 36
    Shows Caution Light 11- 35+
    Warning Light. 28+ 10-
    Just for your info regarding using LED lights we have had two aircraft develope glimmering warning & caution lights. It appears some TCU’s leak enough milivolts to cause this problem. We confirmed it was the TCU by fitting it to an aircraft which had no issues prior & the problem
    followed the TCU. Then fitted to an aircraft with incandescent lights & no glimmering.
    We seem to have solved the problem by fitting another resistor in each circuit.

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