They say the sonar modules will not work under 50 degrees Fahrenheit (10 degrees Celsius). I have tried using the  4, 10 ohm resistors but this seems to work much better, and is easier to install  for me This is how I keep my sonar module warm in the winter, all you need is a small piece of the strip of red LED's, this is where I got mine

http://www.quadroufo.com/product_info.php?products_id=78&osCsid=h227449ro31sm8hvhoo3ge3sv4

make sure to get red, they are much hotter than other colors. (red LED's usually use more power (watts) than other colors)

you only need a piece with 3 leds o it, it wraps around the sonar perfectly (currently cost .46 cents)

Just remove the film for the adhesive and wrap around your sonar, solder the wires to 12v and use a tie wrap to hold it securely.  I hooked mine into my lighting so I can switch them on and off.

here is some pic's.

Here are some Photos showing how to get 6 positions on a Futaba 9C super

It will set them for these 2 switches

go to advanced settings choose PMX-6 CRV

first page 1/2 of PMX-6 CRV  should be set as shown below

Second page 2/2 of PMX-6 CRV should be set like this (below)

Make sure to note the order in the planner when setting up your flight modes, the switching order is not 1-6 in order.

that should do it,