I've posted regarding this issue too. Phone does get pretty hot while running nav and hooked up to a car charger. Haven't heard of any solutions yet. I presume it's probably like a computer. When running a CPU intensive app, things heat up. Maybe performance will improve with 2.1 and along with that the google maps stuff may be better coded in the versions supporting higher os's so we may no longer experience this issue after the upgrade happens.

 

Wow that's really hot. The hottest my phone has ever been is about 42 Celsius (~107.5 Fahrenheit). I always thought my phone would overheat if it went any higher. Did you notice any difference in performance or anything like that at higher temperatures?

 

I had same issue with heat when using sat nav on it altho I don't know what temeperature it got to. It obviously is making its little brain work really hard whilst doing the navigation, my worry would be that I thought the phones shut down automatically if they reach a certain heat... not great if you are in the middle of nowhere relying on it for directions!

I also read somewhere about getting a holder that you can position on the cars heating vents so you can have cool air blowing over it.

 

No idea about fahrenheit but I know my phone has been over 60 degree centigrade and all that's happened is it won't charge the battery.

 

my battery widget also gives me the temp of the phone, and yesterday it went to 48 celcius (118F)