Have you had any luck with this issue? I had a 2008 edge come in the shop today with the same issue. Along with what you described the turn signal indicators were inoperable but continued to work on the exterior of the vehicle. Also the problem only occurs when the vehicle is driven in the rain. With the problem being intermittent diagnosis is being tricky at this point. These systems are only connected by a CAN bus so tomorrow when i have some time with it i will determine which of these systems is most like to be exposed to water. But if i find anything out ill post it here and if have any further input i would appreciate it.
