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Garmin gtn 750

mooney2201

By mooney2201
in Modern Mooney Discussion

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1980Mooney Grand Master

1980Mooney

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4 hours ago, PT20J said:

Interesting -- how do you know it needs replacement? It's a primary cell, so it doesn't get recharged.

"Internal Clock Battery Low" warning and slow acquisition

4 hours ago, PeteMc said:

Is that a Garmin repair or do you just go into a local Garmin shop?

 

Either.

3 hours ago, PT20J said:

Apparently the internal battery is used to keep some memory alive to store the GPS constellation  almanac.1653112702_Screenshot2023-01-29at9_49_00PM.png.7a1e6dbf0dc25e90cb8129be5ceab33a.png

Garmin does not want owners changing the battery and the Dealer provided procedures are not exactly easy to find.  From our friends at Beechtalk:

"My GTN650 was installed in 2013 and has now begun displaying the "Internal Clock Battery Low" warning all the time. Maybe its my imagination, but it also already seems to be a little slower in satellite acquisition on startup.

I was surprised when my (small, but busy) avionics shop said "I don't know, I've never replaced one yet" in answer to my inquiries. They are checking with Garmin, but not yet getting any clear info about their ability to do the battery change vs. the need to send it back to Garmin ($1,000 flat repair fee if I'm not mistaken).

The ICA states that we should expect around 10 years out of the battery, so that's one surprise. But it also says it can be replaced at an authorized repair shop or the factory. Of more concern is the lack of info I'm finding so far on what should be a routine maintenance item for a very common instrument. ICA also states that 1-2 months will pass after first appearance of the warning message before critical low state exists, and even then operational symptoms will be limited to slow acquisition only."

"Dealer GTN 650 Maintenance Manual, 190-01004-01, Rev. 02 (downloaded from Garmin Dealer Resource Center) for full instructions for replacing the battery (page 5-6). The part number for the battery is in the Service Parts List on page 7-1.

Only simple tools are required. No soldering."

https://www.beechtalk.com/forums/viewtopic.php?f=21&t=152260

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PeteMc Mentor

PeteMc

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4 hours ago, 1980Mooney said:

But it also says it can be replaced at an authorized repair shop or the factory.

I thought it could be swapped out by a Av Shop.  Let us know what your shop finally finds.  My guess is that they're supposed to backup the config, change the battery and confirm the config is okay and you're done. 

But then that would be too simple and logical.  So do let us know how many hoops and how high you had to jump. :D  Eventually all of us with a GTN will need to go through this, so the process will be nice to know. 

 

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PT20J Grand Master

PT20J

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$150 labor sounds like an hour at shop rate which is probably the minimum charge and not unreasonable. But since it is easily field replaceable, I would probably buy a battery, remove the cover and replace the battery myself since it doesn’t require more skill or knowledge than operating a screwdriver. 

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hais Proficient

hais

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I had to change the battery once for a 530. The shop charged less than $100. I wasn't surprised that the unit needed a battery - presumably there's a clock that needs to run. Almanac and other data can be stored without needing power.

But I was shocked to discover that the unit had no internal memory - or so I was told. I couldn't wrap my head around that design decision. Reading the 750/650 manual, I saw that a memory card is required to operate...again a puzzling design choice. 

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PT20J Grand Master

PT20J

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20 minutes ago, hais said:

I had to change the battery once for a 530. The shop charged less than $100. I wasn't surprised that the unit needed a battery - presumably there's a clock that needs to run. Almanac and other data can be stored without needing power.

But I was shocked to discover that the unit had no internal memory - or so I was told. I couldn't wrap my head around that design decision. Reading the 750/650 manual, I saw that a memory card is required to operate...again a puzzling design choice. 

Although the manual does say the SD card must be in the unit, once it downloads an update to internal memory it does run fine with the card removed. The only reason I can think that it needs the card is for backup if the internal memory has a problem, but who knows -- Garmin doesn't explain this.

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PT20J Grand Master

PT20J

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36 minutes ago, mooney2201 said:

You must save everything to configure module...or you will loose all settings, and I don't need that aggravation to redo all the settings

You should save settings to the configuration module every time a change is made. If the configuration is up to date there is no problem losing data. But, it never hurts to save again before doing anything. Also, I keep a backup hard copy of the configurations I got from the installer just in case.

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PeteMc Mentor

PeteMc

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3 hours ago, PT20J said:

The only reason I can think that it needs the card is for backup if the internal memory has a problem, but who knows -- Garmin doesn't explain this.

There is an internal SD Card for the backups, at least for the Xi units, it is taped inside to the side of the frame.  I'm pretty sure my Avionics guy said metal tape, but he definitely said you'll see it on the side if the cover is off.

 

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rbp Mentor

rbp

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3 hours ago, PT20J said:

Although the manual does say the SD card must be in the unit, once it downloads an update to internal memory it does run fine with the card removed. The only reason I can think that it needs the card is for backup if the internal memory has a problem, but who knows -- Garmin doesn't explain this.

Garmin database concierge will make one SD card that I can use to update the nav databases in my G3Xs, GTN750 and GNC355, instead of using 4 separate cards. this is of course more important for fleets. the card definitely does not need to be in the unit to operate, and goes against the default database concierge behavior

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PT20J Grand Master

PT20J

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40 minutes ago, rbp said:

Garmin database concierge will make one SD card that I can use to update the nav databases in my G3Xs, GTN750 and GNC355, instead of using 4 separate cards. this is of course more important for fleets. the card definitely does not need to be in the unit to operate, and goes against the default database concierge behavior

Do you keep a card in the G3X for data logging?

Having a card in the GTN is required per the limitations section of the AFMS so it’s technically a violation of FAR 91.9 not to have it although it would have to be a very thorough ramp check to notice that ;)

310244036_Screenshot2023-01-30at9_50_48PM.png.9fd20e89ac3dd7003a7acb17fa1732f7.png

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rbp Mentor

rbp

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6 hours ago, PT20J said:

Do you keep a card in the G3X for data logging?

Having a card in the GTN is required per the limitations section of the AFMS so it’s technically a violation of FAR 91.9 not to have it although it would have to be a very thorough ramp check to notice that ;)

 

yes, I keep SD cards in all the devices! 

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jetdriven Grand Master

jetdriven

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14 hours ago, 1980Mooney said:

Don't forget shipping w/ insurance both ways.......another $80?...more?!

I shipped a G430, insured for four grand, 150 nautical miles away and it was $110 with UPS so it's probably more like 150 each way. 

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