Electrics Posted March 11, 2011 Share Posted March 11, 2011 We have an APU door opening issue. The APU door will not open unless you pull the touchdown relay C/B. I followed the FI and it leads me no where. I could really use some help. I am new to the APU I am us to GTC's. Quote Link to comment Share on other sites More sharing options...
tenten Posted March 11, 2011 Share Posted March 11, 2011 Based on APU DOOR electrical circuit; the possibility of malfunctioning of internal limit switches within door actuator is the cause of your defect. Quote Link to comment Share on other sites More sharing options...
tinyclark Posted March 11, 2011 Share Posted March 11, 2011 Sounds like the wire between C1 of the touchdown relay and pin 1 of the actuator connector is open to me, or the touchdown relay is bad. When you pull the touchdown relay, the door probably is opening to the 15 degree flying position, as it should. Not really a whole lot to go bad for the full open position. If you have 28V at pin 1 with the circuit breaker in, then the actuator may be bad. Not sure exactly what diagram to look at, since I have no idea what model and year you have. Quote Link to comment Share on other sites More sharing options...
tenten Posted March 11, 2011 Share Posted March 11, 2011 Not proper circuit; but might help. Quote Link to comment Share on other sites More sharing options...
NATOPS1 Posted March 12, 2011 Share Posted March 12, 2011 Door actuator is bad, if you have power on the "on ground" pin 1 at the actuator. (test point 10 on our aircraft) If no power at TP 10 check for power at C 1 of the ATR. If power is at C 1 you have an issue with an open wire between C 1 and door actuator as Tiny posted. If there is no power at C1 the ATR is BAD ( No power transfering through relay to "On Ground" C 1 contact.) Power is flowing when the ATR is deenergizes (when you pull the TD Cb) so the power you need is being supplied (on C 2) to the relay and it is being switched to the "in air contact C3) . These points C1,2,3 and TP 10 may not be the same as yours but should be similar. Quote Link to comment Share on other sites More sharing options...
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