Touran EcoFuel 2008 2.0, Gas and Petrol Shift Question

Hi, I'm from Goteborg and recently purchased a 2nd hand VW Touran ecofuel 2008 2.0. I'm a bit confused on when the car shift on petrol and when on gas. There's a small arrow in the dash board shows when it is on Petrol. When I bought the car like three months ago, it was almost all the time starting on Petrol and then after few moments shifting on gas (that petrol arrow goes off). But now since couple of weeks I noticed that it all the times starts and runs on Gas, although Petrol fuel is full but it never goes to Petrol (arrow sign never appears anymore). I googled and found this pdf http://www.volkspage.net/technik/ssp/ssp/SSP_373_d1.pdf and in that page 36 it says that coolent temperature if it is above 15 then it goes to gas mode. But now a days I can see temperature in my dashboard below 15 but it still starts on gas. Now I'm going to end gas cylinder to see if then it shift to petrol or not. Now it's very close to finish, but i'm confused that if there's something wrong it will not go to petrol and i'll be stuck on the road .....
so before that....I want to know about how that works....if anyone knows....

Thanks in advance :)

Have you got any engine/warninglights that is turned on?
If you disconect the contact on the gasregulator the engine will go over on petrol, but you will get a faultcode if you do so

Hi, thanks for the reply. No I don't have any warning lights turned on. I'm not that technical so i don't know where is that gasregulator located....but I'll try to finish the gas over the weekend and update you..what happens...

Over the weekend I finished Gas completely and then it did shifted over to Petrol, and then I refilled the gas back and it started on Petrol and quickly shifted over to gas again. So now at least I know that the shift is working....so may be it's current temperature these days causing it to only running on gas or something....not sure...

Today I went to a local mechanic, he checked all software related stuff and said no, there's nothing wrong.....so still it's unclear why the car is behaving like this :( ....now it's getting cold and car has really hard time starting in gas mode ....
no body knows here i guess too :(