2015 Outback - Issues with AC operation on hot days

[bass5]

I have a 2015 Outback and have been having an intermittent issue with the AC system for a couple years. On hot days with the ambient temp above 90 degrees and I've been driving for a while, the vents will stop blowing cold air with the AC on. When I pop the hood with the engine running, I note the following things:

1. The radiator fans are not running.
2. The AC compressor will run for a second or two and stop. This cycle will repeat every 10 seconds or so.
3. Every minute or so the high pressure relief valve in the compressor will release a puff of refrigerant.
4. The radiator temp gauge on the dashboard may start to creep up, but not always.

If I shut the engine off and let it cool down for a while, the AC will work perfectly fine again (radiator fans will run, compressor runs fine, etc...) Where I live it only gets hot enough maybe 5 or 6 times a year for this issue to present itself but it is of course frustrating for the AC to cut out when it's needed most.

I've taken it to two different mechanics who were unable to find anything wrong with the AC system or radiator. Part of the problem is that the issue only occurs under certain conditions and is not easy to replicate.

Any help or advice on what the issue could be is appreciated.

 

[Dick Foster]

This is one of those times when a coolant (water) temp gauge would be handy.

 

[bmart]

Flow may be restricted in the coolant or refrigerant system. Thermal expansion valve may be on the way out. Any competent mechanic should be able to sort this out.

Have either of these systems ever been serviced?

 

[bass5]

Thanks for the tip on the coolant temp gauge, I will get one and see how high the coolant temp is when the issue surfaces.

I should also mention that the mechanics I took it to checked both the AC system and the radiator, and I was told that both systems were in good shape. The best guess I could get from them was that it's an electrical issue, but the problem went away before any more troubleshooting could take place. I don't know exactly what was checked though, they did not tell me exactly and what was done and I don't know enough about car AC systems to ask specifics.

To me (as a mechanical engineer but not in the automotive realm) my best guess is that it is a radiator/engine cooling issue. If the AC condenser is not able to reject heat to the radiator, the refrigerant pressure will build up in the coolant loop, which would explain both the pressure relief valve and the compressor failing to run.

If the AC system is on, I believe the radiator fans should be always on as well? Since both fans stop working at the same time, what could be causing a lack of power to the fans? I believe the fans are designed to to run at two speeds based on the heat load to the radiator. Could it be the fans run at low speed but are not getting power for high speed operation? How would I check that?

 

[bmart]

Dick wil know better, but coolant system and refrigerant aren't the same. There is coolant for the heater core, but I don't know why radiator fans would need to be on for a/c...

 

[Tumbleweed]

My fans on 2014 Outback come on every time the A/C is on. If it is purging freon, I would think it might be low on freon. I would look at a way to check the low pressure switch.

 

[jesseblair]

I'm having the same problem as you, with a 2011 Forester. Someone today suggested it could be the AC control module. I'm going to look into that and if it turns out to be the problem I'll relay that to you.

 

[bass5]

I'm having the same problem as you, with a 2011 Forester. Someone today suggested it could be the AC control module. I'm going to look into that and if it turns out to be the problem I'll relay that to you.

Thanks and let me know what you find out. My best guess right now is that the issue is the ECM or a bad relay.

 

[roger38327]

I have the same problem as you on a 2015 Impreza.