dart340,
Thanks for that. I've done the cold air test and it's the microcontroller for sure. The solders on the SMT itself look good under the magnifier, but of course that's not the whole story. It could still possibly be a heat problem, combined with a chip that doesn't quite meet the temp spec. The DF was in the hard case in the car, so the board was probably around 100+ F. Setting the unit on the hot ground, in direct sunlight, with the canopy preventing the heat from escaping would perhaps raise the temp another 20 degrees. Now the chip itself is generating heat internally, and there is not enough ambient temperature differential to dissipate the heat, so the temperature will rise even further. The chip is flat black - pretty much the ideal black-body heat absorber in direct sunlight. Once a certain tipping point is reached, I would suspect the chip's internal temperature would climb uncontrollably. I'll also call DFI & Spectrolutions and see what they think.

Ciao,
Bruce