The Garming 430 installation procedure recommended installing a cooling fan to circulate air into the unit. I bought a cooling fan with 3 ports, one for the 430, and the other two to circulate air behind the two Dynon units. I installed plastic tubing between the fan and these three points. However, when I turned on the fan, I got a pretty pronounced whistle, probably a result of the ribbing of the tubing. This was intolerable. I later replaced this tubing with CAT ducting material. This eliminated the whistle problem.
