Very Hot Outside Temps. AC on auto blows hot but AC works OK

[SAR95SportCombi]

2006 9-5 Estate.

When temps outside are hot (over 30C / 85 F), the AC blows hot at all settings when car is started after sitting overnight, but will blow cold if coldest setting is called for. After a while it seems to self correct and AC operates OK on Auto settings again. This seems to coincide with the inside of the car cooling down as it is driven,

This never happens unless the outside temps are high or if the car has already been running that day - ie it doesn't seem to repeat even if the car is parked for a few hours and inside temps climb again. It only seems to happen starting 1st time on hot days when the interior is blazing hot

I'm think this is pointing to a failing cabin temp sensor, but the intermittent nature makes me wonder if there could be more going on

Thoughts?

[Mjollnir81]

Could be the ACC is acting up and/or blend door issues.

Honestly a tech2 I think is needed to better diagnose. If there is a way to calibrate these ACC units on Dame cars I haven’t found it yet.

[GeoffR]

2006 9-5 Estate.

When temps outside are hot (over 30C / 85 F), the AC blows hot at all settings when car is started after sitting overnight, but will blow cold if coldest setting is called for. After a while it seems to self correct and AC operates OK on Auto settings again. This seems to coincide with the inside of the car cooling down as it is driven,

This never happens unless the outside temps are high or if the car has already been running that day - ie it doesn't seem to repeat even if the car is parked for a few hours and inside temps climb again. It only seems to happen starting 1st time on hot days when the interior is blazing hot

I'm think this is pointing to a failing cabin temp sensor, but the intermittent nature makes me wonder if there could be more going on

Thoughts?

When did you last change the cabin filter? I would start with that as if it is blocked it will mean only internal, hot, air is being circulated, much the same as selecting recirculation. It doesn't take long for the cabin filter to get very dirty, mine (NG 9-5) was very dirty after only 18 months.