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Red "Control light" lamp turned on...what does it mean?


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In my CTSW (2005) cockpit there are two red warning lamps; one named "Generator" and one named "Control light". Lately the "Control light" lamp has turned on and off once in a while, but I`m not sure what this lamp indicates. Can any of you tell me?


At the same time, the tachometer seems to be confused, indicating 0000 RPM at idle, but wakes up and operates as normal when RPM increase. Also this problem is on and off.


There was a period this summer when the aircraft was exposed for heavy rain for quite a long time (48 hours continously). I have a feeling that the issue started after that.


Any ideas?

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Before you go hunting too far into the system. Tighten all 5 ground wire nuts and bolts. It will take about 10-15 minutes. This may or may not be the culprit, but could be and in a composite plane should be the first place to check. Consider all ground nuts and bolts hand tight, but wrench loose. Put a wrench on all of them. 4 in the engine compartment and 1 inside the panel on the firewall on the passenger side.

After this is done then check the problem to see if it still exist.

I could be a loose wire, but you absolutely need to tighten the ground first.

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Hmm...is the control light something for the EMS? I have a Dynon EFIS with analog engine gauges, and I only have an alternator light.


Maybe it should always be lit to show the pilot is in control? :)


Or always lit to show the pilot is out of control! . . . :lol:

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A bit of a hijack, but...


...I Googled and found the POH for your plane online, in an attempt to answer your question.


Not a very comprehensive POH, IMHO.


Normally, somewhere in Section 3 would be a schematic of the electrical system, and a diagram showing the instrument panel with each item identified. I did not see the former, and the latter is quite incomplete in its labeling of panel items.


Hopefully, later POH's do a better job.


In any case, one should really know what each switch, knob, lever, indicator, gauge and breaker/fuse does. Not your fault if the info is not provided. Good luck in your search, and let us know what you find.

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Hi terjekolaas,


this is the external alarm-light, which is under control of the Dynon EMS. If any warning about parameters out off the green exists, the light will glow.


The Dynon Handbook says:


Alarm Indicators
Any time a built-in or preconfigured alarm set point is exceeded, you are alerted via both visible and audible (if connected) alarms.
When an alarm is triggered, the following things occur:


The measurement’s value and tick color are highlighted red

The measurement’s value and tick blink

A red alarm bar appears at the bottom of the screen with a message identifying the out of range measurement

Below the alarm bar, the alarm menu gives you options for what to do next. See the following subsections for more information


If an external light is connected to the EMS-D120 EMS main harness, the light turns on
The alarm menu appears below the red alarm bar. See the Alarm Silencing and Alarm Acknowledgement sections below for more information on this menu. Note, alarms may be silenced immediately; they may not be acknowledged during the first half second of the alarm.
In an alarm condition, the EMS-D120 also alerts you audibly, provided the EMS Audio Alert output is connected to your intercom as described in the EMS-D120 Installation Guide. If no audio device is connected, you will not hear an audible alarm.






EMS-D120 Pilot's User Guide.pdf

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Thanks, Eddie and Markus. I indeed agree that the CTSW 2006/2007 POH lacks some vital information. And even if most CT`s are equipped with this warning lamp, none I have spoken with so far knows exactly what it means. We have no Dynon`s installed in our plane, so I guess it has nothing with the Dynon EMS to do. Though, I have feeling it has something to do with the alternator, as MrMorden suggests...


Will check the ground wires this weekend. Hopefully that will shut down the lamp. It still would have been great to know exactly what it means, though...  :)

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It may be the lamp that on my plane is labeled "ENGINE". It is connected to the FlyDat buss and as was said may indicate when some systems are out of tolerance. Could have been the RPM, as was suggested. It sounds like your labels are not the same as mine so I'm not being definitive here - just a suggestion.

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My "control light" seems to be the same as Jim Meades "Engine". This weekend I opened the instrument panel, and followed the wires from the "Control light" to the FlyDat`s "Alarm" section. According to the Rotax manual, the alarm will glow when there are unusual values read from the engine. The RPM-problem is obviously one of those.


As Roger suggested I tried to tighten all the ground wires and bolts, and know everything seems fine again. RPM working as normal and no more "Control light" glowing.


Thanks for your effort guys - you really know your CT`s  :)

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