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FC lights out...and stays out.


keepemflying130
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Have a -16 with an interesting problem during induction runs. During crossover checks it will go to lights out, but the light will stay out. No noticeable correction, but is 830 peak and corrected. Come back to F.I. and light is still out. Go to G.I. light is out. Reverse, you guessed it, still out. Will only come back on on downshift. Until again you go above crossover. All the rest of the TD checks are ok. The light will come on during overtemp protection check, and overtemp correction is provided...check good. Have not done any troubleshooting, or corrective action yet, as this was the induction run. I suppose it could be an amp problem, but I seem to recall the coordinator coming into play. Rigging..wear..?

Any thoughts?

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I\'ve seen this problem twice, and both times it was the coordinator. I promise!!!

Just to be absolutely sure, all you have to do is disconnect the speed switch cannon plug(no jumpers, just disconnect it and let it hang), connect a new coordinator to the two cannon plugs on the back of the coordinator, and put the TD switch to auto. Move the input shaft of the new coordinator up and down from takeoff to reverse repeatedly while someone is watching the fuel correction light. If it keeps popping on when you go below 65ish on the protractor, the old coordinator is bad. This method is quick and painless. Simply disconnecting the speed switch cannon plug fools the TD Amp into thinking the engine is running. This way you can fully ops check the light without even starting up the engines.

The only other component that has direct control over that light is the TD Amp. The signal also goes through the speed switch and the brake lock relay, but your speed switch is obviously good, and I would think your brake lock relay is good since your temp limiting check passes. If the coordinator doesn\'t fix it, try the amp. I\'m 99% sure it\'s the coordinator though.

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This may not relate. Its been a long long time and a lot of brain cells ago but check to see if the light goes out when you push the throttle up to max power static (Power on, engine not running). If the lite goes out at Xover R&R speed sensing control. The 94% switch is stuck. Start limiting dont work and TIT is limited to 1077 on start.

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The Brake Lock Relay will cause the exact same problem. If the speed switch causes the light to go out statically, it may also be a broken connection internally, not necessarily a stuck switch. Afterall, the switch is normally engauged until it exceeds 94%, at which time the switch breaks contact and telling the TD Amp via the brake lock relay to go from start to normal limiting.

The 94% switch is completely independent of the 16% and 65% switches, so you won\'t even notice something is wrong unless you either get a hot start or you move the throttles up statically and observe the lights going out.

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  • 4 weeks later...
  • 3 months later...

Just for a follow up. Ran the plane today to power. Ops checked good. I guess that home station has been having a problem with this engine for about a year. That is the info that I have. Apparently they had some problem at one time that req\'d some electrical troubleshooting. We found 3 terminals disconnected in the main junction box. The one on top of the engine (with the kill switch). Two I know went to the TD valve. Not broken, disconnected, with the nuts finger tight back on the terminals.

Anyway, whatever the original problem was, it was fixed while throwing parts at it trying to fix the problem caused by the disconnected wiring. Work good, last long time. Time permitting, always check wiring. Thought ya\'ll would like to know.

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