A/C cools for some time and then loses its cooling

[Emilbadal]

Hey guys,

I’ve read quite a bit of the A/C evaporator issue thread but didn’t find anything regarding this issue that I’m having. This issue so far happened twice during this summer. The first time the ambient temp was pretty high (~105F). The second time it was ~90. The issue is that when I start up the car the AC cools down the cabin just fine, but after about 30 mins of driving suddenly it starts to lose its cooling performance(It doesn’t blow stale warm air but rather mildly cooled air in comparison to ambient temp to the point that the cabin keeps getting warmer and warmer). The first time that this happened I thought , here we go ,$2000 evaporator leak. As I was driving I turned off AC and then rolled down the windows and blasted the fan. After 5 mins of driving like that I tried again and long and behold AC started cooling again.I’d appreciate it if you could help me out figuring out this issue. Oh btw I changed the cabin air filter a month ago after the first occurrence but then it happened again even after the cabin air filter change. During the second time that this issue happened , I turned up the fan to the max without turning off the AC and I noticed a weird sound coming from the air vents. As if some blending door was stuck half way closed or something.which doesn’t make sense to me because I didn’t change any vent configuration at all. At a later date I turned up the fan to the max and the air flow sound was normal again, as if it fixed itself

P.S. One thing that I noticed that seemed odd to me was that the compressor stays on for let’s say 45-60 secs and the shuts off for about 4-5 seconds before engaging back on again. From my experience from other cars I’ve owned , the shut off cycle usually take 30-45 seconds before engaging back on. But on mustangs I don’t know if that’s normal or not.

Sponsored

 

[Pr1m3Galaxy]

I had a similar issue with a 2011 Ford Fiesta. The car would blow cool air for 5-10 mins then blow slightly cooled air. This issue got worse and worse for me until it finally wouldn't even blow the slightly cooled air. For me, the issue ended up being a compressor clutch going out. Had to get the full thing replaced for like $1400.

 

[Emilbadal]

Thanks for sharing, I never would have thought of that. Next time this happens I have to pull over somewhere and check out if the clutch is engaging completely or slipping.

 

[Pr1m3Galaxy]

Yeah hope it helps. Was a pain to diagnose. The key for my situation was that after the AC had been blowing warm and right when it would go back to cold, you could feel the car jerk a bit when the compressor clutch finally would engage. It wasn't violent or anything that would cause a driving incident. But you could feel the car like hiccup almost. The tech explained that was the clutch finally catching again.

 

[17Magnetic5.0]

I have very limited experience with AC related stuff but it sounds like the system is freezing up and then when you leave it off it defrosts and works fine again. I would check your Freon level, then if it’s fine I would proceed to your cabin air filter, and finally blower.

I don’t think it’s your fan clutch because it wouldn’t cool for 30 minutes like you say. But start with putting in a can of Freon preferably the kind With the gauge on it so you can tell the level as ur filling up.

 

[17Magnetic5.0]

Btw low Freon would also cause the fan clutch to not kick in so it’s probably best to check that before diagnosing the fan clutch.

Sponsored