Thanks Mike for the suggestions. When I power the 740 up with the cigarette lighter power cord, the unit powers up and the screen comes on.Then the screen goes blank just before it goes to the option screen. Sometimes it will begin to play music before it goes blank. I have pulled the power cord out of the unit after it went blank and checked the output of the power cord with a volt/ohm meter and it reads a steady 12 volts. I've done this several times on both cigarette lighter power cords that I own. One is brand new. The cigarette lighter receptical is fine because I have a Garmin 295 that powers up on it and runs fine. Like I said, the 740 powers up and and runs perfect when it is connected to the wall receptical and directly to the 740. It will also run perfect on the 740 internal battery. It is really confusing.
It is hard to believe that both cigarette light power cords would caus the same problem. I may order a new power cord anyway. And also even though I read 12 volts at the output end of the cords, is it possible that the fuses may be causing the problem? Kinda seems ridiculous, but worth a try I guess. If the fuses are too small to cary the amperage, that would not show up in a volt/ohm test.
I was hoping that somepne on the forum might have had the same problem . I talked to iFly technical support and he didn't have a clue. Actually I not sure that I explaned it good enough. He just wanted me to send it in.