G500 GDU 620 rainbow screen - possible solutions?

My G500 has suddenly developed a rainbow screen https://marysun.com.au/assets/Garmin%20G500.JPG . The issue was intermittant last week, but now seems permanent.

There is a GDU voltage alert "GDU has low voltage" but not sure if this is because all other sysytems were switched off when I tested.

Many thanks for any constructive solutions or advice.

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Garmin-AW over 1 year ago +1 verified

Hi there, after working with the field service team on your issue, it doesn't look like this will be something we can resolve here on the pilot side. We recommend taking this to your local Garmin dealer…

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+1 Garmin-AW over 1 year ago

Hi there, after working with the field service team on your issue, it doesn't look like this will be something we can resolve here on the pilot side. We recommend taking this to your local Garmin dealer so that they can get you a resolution. You can find certified dealers local to you here, ensure to select Aviation as the category: How to Find a Garmin Dealer

0 2542422 10 months ago in reply to Garmin-AW

I got the exact same failure on my GDU620, less than 400 hours on the unit. Failed inflight for me, thank goodness it was a clear day. I assume it's gonna need to back to Garmin. Maybe time to consider that upgrade! Going to the Garmin dealer tomorrow

Was your failure resolved, if so how?

0 2542422 10 months ago in reply to Garmin-AW

I had the exact same failure. The unit has less than 400hrs. It happened inflight, thank goodness it was a clear day. My PFD faded to white, then green/blue. I powered it down and when I brought it back up I got the rainbow screen. I'm sure it's gonna need to go back to Garmin. May be time to consider an upgrade! Goes to the avionics shop tomorrow.

Was your problem resolved? If so how?

0 6591467 3 months ago

Based on your description, the intermittent rainbow screen on your Garmin G500, coupled with a "GDU has low voltage" alert, strongly points to an underlying power issue rather than a display failure. The low voltage is likely causing the display to malfunction. As a matter of safety, you should have a certified avionics technician inspect the system to determine if the problem lies with the G500 unit, its power supply, or the aircraft's electrical system before any further flight.

0 6591467 3 months ago

Based on your description, the intermittent rainbow screen on your Garmin G500, coupled with a "GDU has low voltage" alert, strongly points to an underlying power issue rather than a display peryourhealth failure. The low voltage is likely causing the display to malfunction. As a matter of safety, you must have a certified avionics technician inspect the system to determine if the problem lies with the G500 unit, its power supply, or the aircraft's electrical system before any further flight.

0 5440356 8 days ago

The intermittent, now permanent, rainbow screen combined with the "GDU has low voltage" alert on your Garmin G500 strongly suggests a power supply failure to the display unit (GDU) itself. The low voltage condition likely starves the display’s internal graphics processor or backlight, resulting in the corrupted "rainbow" image. Your first step should be to have a qualified avionics technician check the external power circuit supplying the GDU, including verifying the aircraft's main bus voltage, checking the specific circuit breaker, and inspecting the wiring for loose connections or corrosion. If external power is confirmed to be stable and within specifications, the problem is almost certainly an internal failure within the GDU hardware (e.g., an internal power supply board or flex cable assembly), which is a known failure mode for these units. Because this involves flight-critical certified avionics, you should not attempt internal repairs; the unit will need to be removed and sent to a certified Garmin dealer or repair facility for diagnosis, repair, or replacement.