Garmin com - low voltage / high temp warning

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Lownslow79

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Lownslow79
Hi,
I'm part owner in a C-172N where we installed new avionics.
The radio is a Garmin GTR 225A and the transponder is a Garmin 335 with ADS-B out.

After a half an hours flight a warning will appear on the radio stating something along the lines of "low voltage or high temp - reducing output power".

Anyone here who's had the same issue in their plane? Tried swapping with new radio, same issue, so not the radio.

Not sure whether it is low voltage or heat that's triggering the warning. It is mounted in the panel directly above the transponder.

We've got a voltage thingy plugged into the cigarette plug, it shows about 12.8 volts where it drops to around 12.7V.
Voltage sounds low compared to let's say a car or boat, but not sure what's to be expected in the Cessna.

We also swapped the voltage regulator just to check, but no difference.

Thanks!

John
 
You might check the resistance of antenna cable and antenna. If it has more resistance than spec it will require more power to drive antenna.
 
Mikey52 said:
You might check the resistance of antenna cable and antenna. If it has more resistance than spec it will require more power to drive antenna.
Click to expand...
Great advice Mikey, we'll do that! Thanks.
 
Lownslow79 said:
Hi,
I'm part owner in a C-172N where we installed new avionics.
The radio is a Garmin GTR 225A and the transponder is a Garmin 335 with ADS-B out.

After a half an hours flight a warning will appear on the radio stating something along the lines of "low voltage or high temp - reducing output power".

Anyone here who's had the same issue in their plane? Tried swapping with new radio, same issue, so not the radio.

Not sure whether it is low voltage or heat that's triggering the warning. It is mounted in the panel directly above the transponder.

We've got a voltage thingy plugged into the cigarette plug, it shows about 12.8 volts where it drops to around 12.7V.
Voltage sounds low compared to let's say a car or boat, but not sure what's to be expected in the Cessna.

We also swapped the voltage regulator just to check, but no difference.

Thanks!

John
Click to expand...


12.8 volts… is that with the engine running or on battery power?
 
That’s almost certainly your issue (it’s definitely _an_ issue) and you need to have your charging system looked at.
 
Lownslow79 said:
I'm part owner in a C-172N where we installed new avionics.
Click to expand...
Before your mechanic reloads his parts cannon again, you may want look at the aircraft charging system a little better. Having 12.8 volts on your "thingy" is a definite clue your alternator may not be charging or that charge is not making it to the battery.
 
Sorry, I missed the point of less than 13 volts with engine running. At less than 13 volts it's definitely a charging problem. Probably a diode gone if an alternator or a bad set of brush's if generator.
 
Thanks guys. Low voltage issue it is by the sound of things!
 
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