Usually my temp reading sits a little below the halfway line on the temp reading, but the other day i was parked with the engine idling waiting for a friend, was getting hot so rolled up the windows and turned on the A/C and maxed it out to coldest possible setting, 15mins later i noticed the temperature had climbed close to the H on the temp reading and then i quickly looked at the outside temp reading and it read 32degrees!! So in a panic i switched off the car. When my friend finally came down, i got in the car and decided to turn off aircon, turn on the heating to max and gave it a quick blast to force some air into the engine bay, a few minutes later the temperature finally went down to half way but not as low as it usually sits.
That was 3days ago and the temperature has been fine ever since but is there anything i should actually check to prevent this from happening? Or does idling with aircon on have this effect?
Any ideas? Eg thermostat or fan etc...
Thanks
Saskhi