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EFIS Overheat

N

n348pb

Member
After 60 hours of flying with no problems starting back in October, I had a problem with my GRT EFIS screens today. OAT -2C at 12000', 45 minutes into flight my EFIS screens started going blank. They would cycle off for a few minutes and then come back on. I have 3 screens and only the 2 on the pilot side had the problem. They were in the sun and the cabin heat was on slightly but I have flown in a lot warmer conditions with no problems. I also have defog (computer) fans under the glare shield but they are forward of the subpanel so had no effect when I tried to use them to evacuate heat. Has anyone else had this problem and what was the solution? As soon as I turned to RTB the problem went away. Not a good start to my first cross country with my wife! Tomorrow will start with calls to GRT and Stein. :(
 
My cabin has been hot, very hot at times with temp near or above 100F and I have never had my GRT screen misbehave. Unless you have them positioned in such way that you know it will trap a lot of heat, I doubt this is the source of your issue or there is some thing wrong with these two units. I am sure GRT will have a good answer and will take care of the them in a timely manner.

Good luck
 
I have to chime n with Mehrdad - the Texas Gulf Coast gets HOT, and I have never had a problme with the GRT screens overheating - I have no cooling fans under the panel, except what is in the units themselves.

Paul
 
Take a look at your voltage to the system(s). Depending upon what is in the "box", once the voltage falls around 10 or so volts, the first thing that occurs is the screen will go dark. The system is still running but you cannot see anything. Up the voltage and all comes back.

Do you have a secondary power supply to your EFIS?
Were you running low RPM's?
Is your alternator working correctly?


Just some ideas to consider.

James
 
My GRT's work great so far, but no cabin temps above 70F yet. My PS Engineering PMA8000B drops out around 10.0 V, then remaining radio stack and GRT screens go blank around 9.7 V. It has been awhile since I tested the battery, but that is close. GRT will take care of you. Keep us posted.
 
Add me to the low voltage side of the discussion.

When I was doing the setup work prior to actually flying, I experienced this same problem more than once, finally got in the habit of keeping a trickle charger on the battery whenever I was working on the setup.
 
As a follow-up:
I have a battery backup as well as dual alternators and I was running at normal cruise power so I doubt low voltage was the issue. I also keep a battery tender on the battery when it is hangared and this also occurred 45 minutes into the flight. The screens did not reboot as would be the case with a loss of power.

The cockpit was warm but not hot.

The sun was shining directly on the screens.

GRT says it sounds like a heat issue so I am going to use a spare port on my avionics fan to direct air to the back of the screens. Band-aid?
 
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n348pb said:
OAT -2C at 12000', 45 minutes into flight my EFIS screens started going blank. They would cycle off for a few minutes and then come back on. I have 3 screens and only the 2 on the pilot side had the problem. :(
Click to expand...

I'm going with the low voltage crowd on this one. I have had my transponder stop reporting altitude twice because of heat and the EFIS still worked fine. Sounds to me like a loose wire somewhere and that would be typical after flying for a while, something has vibrated loose or possibly a broken connector. I really doubt it is heat, there are many of us that fly in much hotter weather than you'll find in CO and have had no issues.
 
This fortunately is an easy thing to troubleshoot. On the ground while the unit verified working, heat up the behind a panel and have thermometer to record the temp.

You can also easily measure and monitor the voltage supplied to the unit for verification.

As a reference, a friend of mine had an engine out on take off which he was able to land safely with minimal damage. The culprit turned out to be his dual electronic ignition failed due to lack of sufficient voltage. He has dual battery and dual alternator but the complicated setup was in such way that the battery that provided juice to the ignition system was not being charged and he was unaware of it. He has modified/fixed the issue since and have verified everything gets charged.
 
Bill,

Keep in mind an airborne re-boot looks different from what you see at normal boot-up on the ground.
 
Low Voltage

I was installing backup battery and testing it in mine. When the voltage dropped below about 10.5 the screens went dark. Raised voltage back up by turning on trickle charger and the screens reappeared. No reboot.

did yours reboot or just come back on?
 
HX temperature

You can view the GRT HX case temperature to determine if it is reaching the limit and shutting down by go to Set Menu, Display Unit Maintenance, Analog Inputs, Internal case temperature. Of the six GRT HX units that I have, 3 each in two airplanes, one site was temperature sensitive when the sun was on the glare shield. but as I looked behind the panel, I realized that the map box and transponder blocked in the HX and there was no air flow possible until I added a fan.
 
Tom... thanks for the input. Does the unit mx screen show history or just current? I'll look at it tomorrow.

As to voltage- all 3 screens get their power from the same bus except that only 1 and 2 get power additionally from the backup battery. #3 never quit which would indicate the main bus power was fine so if it was a power problem it would be in two independant power leads from the main bus to the units - not likely. Also, the problem went away when I turned back to home and got the sun off the displays.

In looking at it today the "defog" fan is directly above the units in question and nothing else around them so circulation shouldn't be an issue. I added a duct off my avionics fan and vented it directly between the units. I'll test fly it in the next couple days and see if I can repeat the problem.
 
current

Bill pretty sure it is just the current. I wonder if the demo mode saves that level of detail?
 
HX overheat

I believe it is an overheat problem. I never had the problem the first summer (2010) I flew the airplane it wasn't until the winter time when I turned on the front heater I saw the problem the first time.

After talking to the GRT people I began monitoring the internal case temperature as described above and found that it didn't take all that long for this temperature to reach the 155 degree (I believe they said) before the screens would go black. This does not hurt the screens and is there to prevent damage from an overheat.

So the problem is not likely to exist for the people who live in the warmer climates. However, it does exist for us in the cold climates especially on long trips at high altitudes when we need to run the heaters. when I fly these trips I try to run the rear heater only and only the front heater when and only if needed but with as little heat as possible and still have creature comfort.

I have thought about making a deflector for the heat duct outlet to direct the airflow rearwards immediately as it exits the tunnel. There is a tremendous amount of hot air coming out of these ducts when the heat valve is fully open. A large percentage of that heat is trapped under the panel and cannot possible be exhausted out fast enough by two little computer fans.

In my case it was the MFD located right next to the radio stack that would go black. The radio stack generates a lot of heat on its own and only makes the problem worse.

The cure in my case so far has been to run the forward heater as little as possible.
 
I could see one at a time overheating, but unless they are interconnected somehow, I wonder why he loses both together. You are right about the front heat...at 20F OAT(our coldest flying temp so far) my front heat is only about 10-20% open and rear 30-50% open.

This is the exact reason one should install two different brands of glass if going ifr. Sure glad I did now.
 
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Ivan,
In your opinion, are both heat muffs needed. I have contemplated using one for cold and only the other for hot air and splitting the hot between the front and rear. the cold would be run directly into the tunnel and I was planning on a couple of vents directly from the tunnel to the foot wells. I live in the midwest, and it rarely gets below 15 F.
 
I made an adjustable aluminum cover that rotates to block my side of the front tunnel heat. I will have to take a pic. I made it because my wife likes her feet to roast. She doesn't have them up by the rudder pedals like mine. It gets really hot up there. I think my shoes would melt if I opened my side and had her flying with me.
 
Cabin heat issue.

Bill,
I believe that one would be enough, there is a tremendous amount of hot air flow out of just one heat muff when fully open.
I think ducting some cold air into the tunnel and possible into the cabin from there might be a good idea, the problem is going to be be where to tap it from.
I certainly wouldn't take it from anywhere in the engine compartment so it would have to come from a NACA inlet somewhere in the side of the airplane south of the firewall.

I like Sean's idea of of a plate to partially block the left side heat outlet, I might try that. I too have two different types of EFIS screens. Two GRT HX's on the left and a Dynon D-100 on the right.

Sean, how about you make available to the market place a small device that would turn the airflow 90 degrees as it exits the tunnel and perhaps slightly downwards. Such a device would reduce the heat problem behind the instrument panel, a problem (I believe) we all have to varying degrees.

Remember. the one thing that is sure to destroy an electronic component is "TOO MUCH HEAT"
 
If you did not have the front vent it would not be quite as comfortable. Anything above 0c I do not use the front. As it gets colder I open it more and more. The only time I have ever had to open it right up is below -20c. Usually I only open it just a touch to make it the most comfortable. It is nice to be able to crank it open on the ground though. You would miss the front heat if you did not have it. I always fly with my coat in the back, so if you had a jacket on it would be different again.
 
Ivan...
I am at least glad to see I am not the only one who has had this problem. It at least confirms my suspicions that it is a heat problem. The idea of a 90 degree turn for the forward heat duct had occurred to me and seems like an easy mod. I think I will also look into getting a higher output computer fan to exhaust the air as well as increase the defog capability should l need it. With the addition of the avionics fan tube I installed it should significantly increase the airflow across the backs of the instruments.
 
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