If you mean the climate control unit (with the buttons and green lights - the thing that controls the cabin fan) randomly turns off and on (the screen goes REALLY REALLY DIM) without you doing anything, then there is a simple fix that dosn't cost a dime. That unit is called the "Final stage unit"
It's a common problem with these where the constant heating and cooling of a specific capacitor, causing expansion and contraction of the metal leads to stress the solder around the leads, causing the capacitor to loose contact with the board, rendering the unit unuseable.
The accepted notion is to think that the capacitor itself has failed and to buy a new one at radioshack for some 1 dollar or wahtever redicuious price they charge and replace it. Replacing it is a total pain since you have to scrape the enamal off of the PCB and around the capacitor to get it loose, AFTER you have de-soldered it.
The real problem, is not the capacitor itself, but the connection TO the capacitor. The capacitor leads simply need resoldering. I know this because I've done this myself and I've read a report where someone just re-soldered the leads and it worked perfectly for him to this day. I can attest to this as well since I did this about 6 months ago, I still have the "replacement" capacitor still in it's (huge) radioshack packaging since I never used it. Here's a link to the main article that describes the DIY to replace the resistor Here's a macro picture of my final stage capacitor.
You may want to add a bit more solder when doing this to ensure it dosn't happen anytime in the future since it looks like there's barly any solder on there to begin with.
Cheep soldering iron and a small spool of solder and "maybe it will work, either way it's worth a shot since the thing's dead anyawys": $5-10
New final stage unit: $450