Recently this month I have been having issues getting my Astra to start first time. It seems the initial Revs where below the 600 RPM needed to keep the car Idle. Sometimes it would be over ( would start ) and sometimes under ( conk out ). One thing I did notice however was when the car did start from Idle , the fans would stay on at full speed even if the car was freezing from the night before! This gradually got worse with the colder weather until I had to call out the trusty RAC to help! Upon further investigation by a professional ! , the Issue was the Engine Coolant Temperature Sensor which tells the onboard computer what the engine temperature is so that the optimum driveability is realized while the engine is warming up ( more fuel is added) and when the engine has reached operating temperature the engine is kept in that state ( via the fans ). Upon the disconnection of the cable to the ECT the car would start fine due to the standard amount of fuel being plugged into the engine instead of the wrong fuel injection due to the defective ECT. This was a temporary solution however the ECT (or commonly called the CTS Coolant Tempurature Sensor ) needed replacing as without it the car is put into “Safe Mode” where the fans will run at full speed for the entire time the car is running even with the Key out! This would run down the battery in a matter of hours , so to fix this the only method was to run the car with the ECT disconnected then when parking , reconnect the ECT lead to stop the fans! A new ECT cost me £12 and can be found by googling your car manufaturer and parts and your local area and ringing round to confirm stock! Click for Larger Pictures The ECT is located as on the picture and will have a cable connected to it with a clip on the side that needs to be pushed to release the cable. Once this is released you can unbolt the ECT with a spanner. Careful , if you have just been for a ride , there will be a gush of boiling engine fluid after the ECT is removed. Screw in the new ECTand tighten with spanner. Check your engine coolant water ( the yellow capped container nearest the  windscreen on the right hand side )and top up if needed. Reconnect cable and problem solved for £12!