Sandel Fade Out

While on my way from New Orleans to San Diego recently, I encountered freezing conditions of 3 Deg. C. OAT.
As expected the wind shield started to fog up so I set the heater to full defrost.
After 30 minutes in these conditions I noticed the Sandel begin to fade out from the bottom up. I adjusted the intensity to the minimum intensity visible suspecting over temp conditions. This had no effect and the data projection continued to vanish.
Suspecting heat as the problem, I turned off the heater and gradually the data became visible again.
Upon arrival in San Diego, I took the aircraft to my Cirrus service center, Crown Air, to inspect the Sandel. They found the internal fans to be functional and the operational temperatures to be normal in ground test conditions. They then checked for loose air ducts that might be directing defrost heat towards the device and found all to be normal.
The summary from the avionics manager was that the over heating must be the product of too much ambient heat behind and around the Sandel in the above conditions.
I would appreciate any comments or details about similar experiences.
Jon Martin
SR-22 # 134

I would go after the remote flux gate/ gyro box. check the heat connections there. Hope it helps. Did you get a overheat/shutdown indication on the HSI? Hope this helps…Ed

Thanks, I did not get any error display on the Sandel.
I will mention the flux gate idea to my shop.

Why would a flux gate or gyro problem cause the display to fade?

Had the same thing happen to me recently. I am not sure of all the facts, but here is the scenario. While my original Sandel was being repaired at the factory in Jan. 2002 a replacement unit was temporally installed in the SR22. On a flight from El Paso to Santa Fe the unit stated to go dark, progressively from the bottom to the top over a period of 10 minutes. Turing the unit off and then on fixed the problem and I had no trouble for the remainder of the trip, and the 3.5 hour flight back to Houston. When I called Sandel I was informed that that the temporary unit that was installed was an older version with a different case. This case is more susceptible to overheating causing the blackout condition. I am not sure when Sandel made the modification to the case. My plane was delivered in Dec. 2001. Have not experienced the problem with the original unit that is now back in the plane. If this problem ever occurs, turn the unit off for a minute or two and the screen should come back to life. A little disconcerting in IMC conditions. Check with Sandel to see what case you have. Hope this helps.

Stuart Herbst SR22 N556L

If you get the box to hot you get a overheat warning that will shut down the hsi…Ed