Garmin com - low voltage / high temp warning

[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

 

[Mikey52]

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.

 

[Lownslow79]

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.

Great advice Mikey, we'll do that! Thanks.

 

[aterry1067]

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

12.8 volts… is that with the engine running or on battery power?

 

[Lownslow79]

12.8 volts… is that with the engine running or on battery power?

That's with the engine running at about 2400RPM

 

[Ryan Klems]

That’s almost certainly your issue (it’s definitely _an_ issue) and you need to have your charging system looked at.

 

[Bell206]

I'm part owner in a C-172N where we installed new avionics.

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.

 

[Mikey52]

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.

 

[Lownslow79]

Thanks guys. Low voltage issue it is by the sound of things!

 

[brian@hiddencreekbuilders]

I am having a similar problem with my avaionic upgrade. I am running a G3X with G5 backup and all new garmin radios. I am showing 13.8v on the G3X with the engine running at 2400 rpm. COM 2 radio will show a low voltage overtemp warning "press enter to continue" This does not happen to COM 1 radio and I do not have any other electrical issues, which makes me think it may be an over temp issue. Any thoughts would be appriciated.

 

[FORANE]

I am having a similar problem with my avaionic upgrade. I am running a G3X with G5 backup and all new garmin radios. I am showing 13.8v on the G3X with the engine running at 2400 rpm. COM 2 radio will show a low voltage overtemp warning "press enter to continue" This does not happen to COM 1 radio and I do not have any other electrical issues, which makes me think it may be an over temp issue. Any thoughts would be appriciated.

Welcome to POA.
Your analysis is likely correct.
Email this guy: g3xpert@garmin.com

 

[asicer]

I am having a similar problem with my avaionic upgrade. I am running a G3X with G5 backup and all new garmin radios. I am showing 13.8v on the G3X with the engine running at 2400 rpm. COM 2 radio will show a low voltage overtemp warning "press enter to continue" This does not happen to COM 1 radio and I do not have any other electrical issues, which makes me think it may be an over temp issue. Any thoughts would be appriciated.

Slide out and swap COM1/COM2 to see if the problem follows the radio?

 

[brian@hiddencreekbuilders]

Good plan. I will ask the avionics shop to swap the radios and see what happens.

 

[FORANE]

I looked but couldn't find the Garmin spec for voltage that triggers that alert. My lancair has a gtn650xi that displays the message you posted every time the gear cycles in flight. My alternator and batteries can't supply the gear pump voltage amp draw, the ship voltage drops and the GTN displays the message... I also have a G5 in the plane; I haven't noticed any change from it when the voltage drops. My G5 has battery backup; possibly this is why it doesn't trigger a warning?

 

[Pinecone]

Before you start pulling apart the alternator, try the simple things. Check that the connections are clean and tight. That the wires are intact and not failing.