I have a Ft-400XDR mounted in my truck and I have a problem with APRS. When its warm out and the sun is shining with the windows up the APRS does not work. The head is not mounted in the sun light. The radio will beacon and key the radio but no packet sound will come out. I check and it gets GPS signal and like I said no packet audio will come out but does key the radio. I tried resetting the radio and no good. Had this problem before so I re programmed the radio and it worked good for a year. So I tried that again but still does it so must been a fluke. This only happens when its warm other wise it works fine. Anyone else had this problem or know what is causing it? Thanks.