Hello,
I've been lurking here finding lots of useful information so I thought I should share about a problem and solution I've had.
I have a 2012 i30 GD Premium and about a year ago the ambient temp (as seen in the dash) sometimes started showing "---". The error occured at random, when first turning the car on but also during driving coming on and off.
Not getting any ambient temp also means the AC stopped working (when getting temp reading AC worked). When able to get the temperature reading I also had problems with the AC taking long to get cold (i.e 10 minutes of driving or longer, sometimes it was instant as it should), however I was focusing on getting the temperature reading problem solved first.
I replaced the temp sensor located at the front. Measured the new one as well as the old one, both measuring the same resistance.
As the error wasn't constant I was pretty sure it was related to some kind of glitch, either connectors or cable. Measuring the voltage going in to the ambient sensor it was OK but I replaced the cable anyhow without any luck.
Found some schematics online and noted that the temperature sensor is somehow connected to the AC control panel (I have a automatic one). Sure enough, removing the AC control panel showed that one of the cables wasn't fully inserted, just enough to cause my problems but all functions on the panel worked (lights, switches, temperature control etc).
This caused:
-No ambient temp in dash
-AC not working properly, AC switch turned on didn't hear the compressor turning on (a slight change in engine noise when you enable/disable AC). I think this glitch caused the AC compressor to turn on/off at random, hence my experience with longer time before cool air was coming.
