GNS 480 failure

I have a GNS 480 in my RV-8. It sat in the hot sun all day at Airventure yesterday and I don't have a canopy cover. I imagine the cockpit got pretty hot given the sun was out and the ambient temp was in the mid to upper 80s. When I turned on my avionics master the 480 failed to boot up, there was no sign that it was even receiving power that I could detect. I reset the circuit breakers several times and cycled the power switch multiple times. Eventually it did boot up and operated normally. However about 15 minutes into my flight it failed again. I eventually got it to fire up and operate normally after about 3-5 minutes of cycling the power switch and CBs.

After the first failure I assumed the temp limit had been exceeded and that the unit has a self preservation logic to prevent damage. I notice in the installation manual that the operating range upper end is 55C or about 135F. It wouldn't surprise me if the avionics got that hot with the canopy closed all day. However when it failed the second time the unit should have been well below the max op temp.

I am now concerned that the unit may be defective, It did boot up properly once I landed and cycled the power but I have lost confidence in the unit. My home airport is in Class C airspace so I need comm to enter and get home. For now I am looking at purchasing and carrying a handheld transeiver and hoping it has the 10 mile range to talk to ATC.

Any advice, experience, or troubleshooting suggestions would be appreciated. I have been flying the unit for over 3 years since I purchased the plane and am otherwise very pleased with it. Given that the unit has been discontinued I am not sure how to proceed if it continues to fail. It is my understanding that the unit can still be serviced at Garmin, is that true? I recall it is a minimum $500 charge to open the box, and if it is an intermittent problem will they be able to accurately diagnose and fix it?

Thanks in advance

The minimum charge for repair (at least for a 430W) is $900.

Sounds like it got hot, wouldn't turn on, then cooled down slightly and let you run for a while (but was still really hot, near its temp max). The fan in back probably couldn't keep up and it quit again.

I would guess if you start from ambient temp rather than a heat-soaked sauna temp, it'll run fine from here on out. Shop for a canopy cover while you're at Osh. It'll be way less expensive than a trip to the shop for your 480.

Concur with Kurt. Make sure the 480 fan runs and stays running after boot up (can't hear it with engine running), and that you have adequate ventilation and unobstructed airflow behind the panel. I left my canopy cover off for most of Monday (for judging) and the cockpit must've reached 150+ after a couple hours.

It's not $900 for a first glance. It's $900 for flat rate repair and complete overhaul, no matter what is wrong. This is after the expiration of the factory warranty.

Actually the GNS-480 flat rate is $1,100, not $900.
https://fly.garmin.com/fly-garmin/support/warranty-information/out-of-warranty

The point is still the same though. If $3,000 worth of parts went bad, you're getting a pretty good deal.

On the GNS480 discussion group you've also had a few folks advise to remove the unit from its rack and re-seat it. That's good advice. While you're at it, visually inspect the fans to ensure they aren't clogged with dust etc. The advice to power the unit and listen for the fans to continue running is likewise very sound advice. These are pretty robust boxes, so it's likely the heat of the cockpit exacerbated a situation of clogged fans, inadequate hot air exit path etc. Exhaust all your low-cost options before sending the unit into Garmin.

While at the show, why not pick up an Icom or similar backup radio that is battery powered. There are specials all the time. If you do, be sure and get headset adapters... or you can't hear it in flight.

What he said, I had one of these radios and mine was notorious for not staying racked nice and tight. I would have to remove it from the tray then slam it back in and tighten the racking pin as hard as I could. It would stay racked and operate as advertised until the next re-rack, usually a few months. Sounds a little harsh but worked every time.
If I recall correctly I got that advice from Stein .

Canadian_JOY said:

On the GNS480 discussion group you've also had a few folks advise to remove the unit from its rack and re-seat it. That's good advice. While you're at it, visually inspect the fans to ensure they aren't clogged with dust etc. The advice to power the unit and listen for the fans to continue running is likewise very sound advice. These are pretty robust boxes, so it's likely the heat of the cockpit exacerbated a situation of clogged fans, inadequate hot air exit path etc. Exhaust all your low-cost options before sending the unit into Garmin.

Click to expand...

I've had my 430W do the same thing after a day on the ramp at Mojave, 10 minutes into the flight it booted properly and has never repeated that fault.
Run it until you see you also have a problem at normal temps.
Reseating it good advice also. My 2 cents
Tim Andres

Thanks all for the advice. I did verify the fan worked after I landed. I have had problems where the radio gets into an intermittent TX/RX mode due to poor seating in the rack, but never complete power failure. I suspect it was the heat given the concensus on the forum. I did drop by the airport today and turned on the avionics 2x and it booted normally each time. Looks like a handheld radio and canopy cover are in my future.

Pull your 480 and file some of the rack front edge off so the 480 will seat deeper. Just be careful and not get metal filings in anything. This helped my 480.

Filing even 0.010" off the front edges of the rack will make a big difference. I went closer to 0.020 when it became clear the radio wasn't making contact with several connector pins. Now I can grab the face of the radio and wiggle it and it appears all the connections are solid.

FIXED

Thought I would let you all know that I have located the problem. Before I committed to an $1100 repair I wanted to make sure I had eliminated other possibilities. Suspecting a power issue I started at the circuit breakers and measured the resistance loaded and unloaded. I also checked the voltage drops across the breakers. In a totally accidental way I discovered the problem to be a bad crimp connection on the cold side of the C/B. As I was checking the voltage drop I noticed the GNS powered up. When I removed the multimeter the GNS lost power. My multimeter lead was actually bridging the bad crimp connection and completing the circuit. Luckily the intermittent problem was in a fail mode as I was checking the C/B or I might have missed it. Now I have $1100 to put toward ADS-B

GNS480 Failure while flying

Hi all,

I flew my RV-7A from Florida to CT today. A six hour flight with one stop. Five hours into the trip, the GNS-480 screen warned of "Loss of communications to COMM" and "Loss of communications to VOR". After this notification, I was unable to tune any COMM of VOR frequencies.

Shortly after that I started to get strange navigational signal to the GRT EFIS. The EFIS was navigating by the GPS, but it changed to navigating by the GNS-480 VOR radial (which I was unable to change). This rendered the GNS-480 compleetly useless...

I switched the EFIS GPS source over to the secondary ADS-B GPS and started navigating with the internal GRT EFIS flight planner.

Powering OFF the GNS-480 for over 30 minutes, then powering it ON again, did not fix the issue...

This unit has been operating flawlessly for almost 1400 Hrs.... I'm planning on pulling it out of the plane tomorrow and see if I can fix the issue myself... I'm not looking forward to spending what Garmin wants to fix it....

Don't discount the idea that a circuit breaker cant go bad either.

I had a pop out circuit breaker go bad once.

It was pushed in, but if your moved the button with the tip of your finger you could see intermittent contact.

GNS480 Failure

Definitely not power related. My local avionics shop took a look at it and came to the same conclusion. Turns out he sent the radio back to Garmin in 2009 (while under warrantee) for exactly the same issue. This time it's not warranteed.... It's at Garmin now. I should know in a week or so just what the repair will cost....

jeffsvan said:

Don't discount the idea that a circuit breaker cant go bad either.

I had a pop out circuit breaker go bad once.

It was pushed in, but if your moved the button with the tip of your finger you could see intermittent contact.

Click to expand...

GNS480 Failure

Ok, So I got my unit back from Garmin yesterday. They replaced the NAV/COMM board, which fixed the error described below. Now none of the knobs are functional! I still can't change frequencies, change GPS way points, or even change the volume of a radio. The softkeys appear to work, but the knobs don't.

How can an FAA Authorized Repair station release a radio, stating that it's able to be returned to service via 14 CFR 43.9, and still have this type of issue? Talk about really bad quality control!

And I still had to pay the shipping charge to ship it back to them for further repair! And, according to the Garmin dealer I've used in the past, exactly the same issues happened in 2009 when this radio was sent back TWICE for the same repairs....

Time to call their customer service number and complain....

Fred.Stucklen said:

Hi all,

I flew my RV-7A from Florida to CT today. A six hour flight with one stop. Five hours into the trip, the GNS-480 screen warned of "Loss of communications to COMM" and "Loss of communications to VOR". After this notification, I was unable to tune any COMM of VOR frequencies.

Shortly after that I started to get strange navigational signal to the GRT EFIS. The EFIS was navigating by the GPS, but it changed to navigating by the GNS-480 VOR radial (which I was unable to change). This rendered the GNS-480 compleetly useless...

I switched the EFIS GPS source over to the secondary ADS-B GPS and started navigating with the internal GRT EFIS flight planner.

Powering OFF the GNS-480 for over 30 minutes, then powering it ON again, did not fix the issue...

This unit has been operating flawlessly for almost 1400 Hrs.... I'm planning on pulling it out of the plane tomorrow and see if I can fix the issue myself... I'm not looking forward to spending what Garmin wants to fix it....

Click to expand...