2010 Subaru Forester AC works sporadically

I have a 2010 Subaru Forester 2.5x, and I’ve been struggling with the air conditioner for over a year.

The AC works amazingly when the car has been shaded / in a garage (even if the garage is not air conditioned - so the garage temp is probably still 90 degrees). The problem is when I’ve parked the car outside in a sunny area. Then, it takes about 25 minutes for the AC to blow cold air consistently. In this case, the fan w blow hot air with tiny spurts of cool-ish air, but nothing that meaningfully cools my car. I live in Texas, so the car is HOT; I’m not expecting instantaneous cooling, but after 3-5 minutes of driving, I would hope it would be getting cooler in the car.

I park in full sun at work, and then drive to pick my kids up from daycare. The car is hot and stays hot until we are home. Of course, I roll down the windows, but I’m always pulling the kids out of the car sweaty and overheated. Lately, it’s turned super-warm, so this is getting more miserable and dangerous for the kids.

Coolant was replaced seven months ago with little effect. I have no idea what could be causing this, although I suspect it’s something related to overheating / a sensor or thermostat since it only happens when the car has been parked in the sun.

Has anyone else experienced this? Internet sleuthing reveals everything from o-rings, compressor, compressor clutch, oiling the bearings or clutch plate, cylinder head gasket, etc. I’m not very car-savvy, but I am worried about my kids’ safety.

Have someone check if the compressor has a thermal limit switch. And if it does, have them test the switch for proper operation.

The thermal limit switch cuts power to the compressor clutch if the compressor should begin to run hot.

Years ago you could just order and replace these switches. But these switches are getting hard to find. So if there’s a problem with the thermal limit switch, the compressor is usually replaced.


Maybe an issue with the sun sensor? Any use of a sunshade, dash pad, papers or misc. whatever left on top of the dashboard?

Tester: Thanks, I’ll ask about that - it’s going back to the dealer on Friday - but they tell me they can’t do anything unless I can bring it to them when it’s not working (not exactly convenient since I’m often on my way to somewhere I need to be!). This does seem probable - the issue is clearly related to being direct sun, possibly exacerbated by the car being black. Once I’ve driven some - at which point air passing over the mechanism might cool it sufficiently? - it works again.

ok4450: Yes, sometimes (when I remember!) I do use a sunshade. My sunshade is one of the accordion-fold foam ones with reflective material. Fairly thick (almost like a very lightweight camping sleeping pad). Nothing else on top of the dash. I’m intrigued, though - I did a little Googling, but I’m not super-sure I understand what a sun sensor is and how this might matter. I’m so appreciative (and very sorry to seem obtuse), but can you tell me more?

Here’s a very brief notation on sun (or solar) sensors.


They’re essentially a photovoltaic diode that produces a tiny voltage when exposed to sunlight and provides some input to the climate control system.

I haven’t had a chance to get into it yet but over the last few days the A/C in one of my cars has become a bit erratic and I’m mildly certain that the sun sensor on it has gone stupid.
I’m north, or maybe east, of you in OK so I fully understand about needing a properly functioning A/C. :slight_smile:

Oooh, thank you! I’ll be sure to ask about this. Today, just for variety, I parked in full sun at work (like usual), but did not put my sunshade up. I’ll see if this changes anything…