Air Conditioning Malfunction

[robrichtx]

Good Morning -

I have a 2015 Mustang GT PP and am having an AC problem.

AC functions pretty normally at speed (30+), but starts to blow warm when stopped or moving slowly.

I scannned ODBII codes and nothing came back.

Seems to be caused by lack of airflow over the radiator, so I'm suspecting engine fan? There appear to be at least 3 relays and 3 fuses connected to various fans. Fuses appear good.

Anyone lose a relay on their Mustang?

I have an appt at the Stealership, but I want to drive it over the weekend.

Thanks in Advance -

Sweaty Rob

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[Jay-rod427]

99% chance evaporator core leak, and low on freon.

 

[foghat]

Yep. Probably evaporator. As of late, it seems a lot have been going on people in warmer climates.

Given I am not in a very warm climate, mine will likely fail next summer of the following - when I am out of warranty.

 

[robrichtx]

Wouldn't a leak cause a full failure though? Warm air all the time, rather than the cold air I get when the car is at speed on the highway?

 

[Jay-rod427]

Has nothing to do with speed, more to do with rpm. When the system is low it will still cool to a point. When it gets too low it stops completely(low pressure cutoff switch). But when it's low and not as efficient the compressor can do it's job well enough at low rpm. but when driving the compressor spins faster and cools better.

Even a perfectly functioning system outputs a drastically different temp at idle vs revs.

 

[foghat]

I'm not an expert, but I would think the additional air flow when moving would help compensate for low refrigerant?

Are your fans coming on at idle?

At idle do you get 'cooler' air out of some vents and warmer out of others?

I can't remember which way it goes, but at idle if you are getting air that is cooler out of, say, the driver vents and warmer out of the passenger vents, it is most like low refrigerant - at least in my experience with my BMW.

 

[TomcatDriver]

Check your fans. I had a Honda doing this and I found that the auxiliary AC fan was not coming on with the AC. AC worked fine above about 30mph.

 

[jasonstang]

Sounds like low refrigerant. I bet if you rev the engine up when not moving the AC gets colder.

 

[robrichtx]

Easy enough to test. Will check, and thanks for all the input guys

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