Air conditioning issue

[Drmklr]

Hey all!

Took the car for the longest drive since I’ve owned it today, 200 miles (about 4 hours with traffic). I never noticed I guess because I’ve never driven it this long in one shot, but at some point during the drive the AC stopped blowing cold.

I got to my destination, got back in the car about 25-30 minutes later to grab dinner and the AC was ice cold again.

Some of the research I’ve done I can see that there are some AC issues in these cars, however from what I gather the AC just stops working it’s entirety.

Thoughts on what might be wrong? Maybe just a recharge?

2017 with 8,400 miles on it.

Thanks for any thoughts.

Sponsored

 

[SH!FT]

Hey all!

Took the car for the longest drive since I’ve owned it today, 200 miles (about 4 hours with traffic). I never noticed I guess because I’ve never driven it this long in one shot, but at some point during the drive the AC stopped blowing cold.

I got to my destination, got back in the car about 25-30 minutes later to grab dinner and the AC was ice cold again.

Some of the research I’ve done I can see that there are some AC issues in these cars, however from what I gather the AC just stops working it’s entirety.

Thoughts on what might be wrong? Maybe just a recharge?

2017 with 8,400 miles on it.

Thanks for any thoughts.

There's 3 things that I know of that should cause a properly working AC system to cycle off:
1. If the cabin evaporator reaches 37F. This prevents the cabin evaporator from freezing over .
2. If the cabin temperature setting is met. The AC will cycle off to maintain your chosen temperature.
3. If the static AC system pressure is less than 40psi. This will not allow the AC system to cycle on.

Sitting for a half hour after a long drive probably got the engine bay super hot which would boost AC system pressure.

When it stopped working:
What was outside temp?
Highway, city stop and go, or stuck in traffic at the time?
What were the climate controls set at? (fan speed, etc..)

Assuming that it's not super cold out... If it happens again with max cold and max fan speed blowing on your face: Pull over and idle. Listen if the compressor is engaging and watch for a condensation puddle under the car. You can also pop the hold to check if the suction line is cold or sweating.

 

[sk47]

having to turn heater way up to get hot | 2015+ S550 Mustang Forum (GT, EcoBoost, GT350, GT500, Bullitt, Mach 1) - Mustang6G.com

No heating | 2015+ S550 Mustang Forum (GT, EcoBoost, GT350, GT500, Bullitt, Mach 1) - Mustang6G.com

Hello; Two currently active threads may be worth a look. As in these two threads about lack of heating, your AC issue may be related. The key is that the AC stopped and later began to work. Makes the possibility one or more of the blend doors are acting up.
In the case of the two threads the issue is heat but these blend doors control the flow of air in both cases. The idea being one or more of the doors could be sending air the wrong way at times. Just a guess to be sure.

 

[Drmklr]

There's 3 things that I know of that should cause a properly working AC system to cycle off:
1. If the cabin evaporator reaches 37F. This prevents the cabin evaporator from freezing over .
2. If the cabin temperature setting is met. The AC will cycle off to maintain your chosen temperature.
3. If the static AC system pressure is less than 40psi. This will not allow the AC system to cycle on.

Sitting for a half hour after a long drive probably got the engine bay super hot which would boost AC system pressure.

When it stopped working:
What was outside temp?
Highway, city stop and go, or stuck in traffic at the time?
What were the climate controls set at? (fan speed, etc..)

Assuming that it's not super cold out... If it happens again with max cold and max fan speed blowing on your face: Pull over and idle. Listen if the compressor is engaging and watch for a condensation puddle under the car. You can also pop the hold to check if the suction line is cold or sweating.

Thank you for the reply. Controls were set to lowest temp setting, AC button on and Auto on. At one point I did put max AC on, however no change in air temp coming out of vents. I would doubt the cabin temp was met as it was boarder line uncomfortable inside. Outside temp, mid 70’s.

when I got to my destination, car still running, I did open the hood to see if the compressor was running. It was. Turned AC off and it kicked off, put AC back on and it kicked on.

I do have to take this drive back home, so I’ll be more attentive now that I know better, see if I get the same problem.

 

[SH!FT]

No problem. Just did some AC work so it's fresh in my head. The suction line that should be getting cold is the hose I have cut by the fuse box in the pic below.

If the system is still cooling, move on to flow as @sk47 has recommended.

If you find it's not, you can check the pressure by connected a gauge to the low side. The pressure between the high and low side will equalize once the engine cools. The gauge should be purged of air before opening the valve to avoid introducing moisture to the AC system. My factory charge was 95 psi on a 92F humid day. The 2020 mustang is R1234yf refrigerant. I envy you if the 2017 R134a. Good luck!

 

[Drmklr]

At this point, no cold air coming out at all.

 

[Paul McWhiskey]

If you are running it with the coldest setting and it produces cold air for a while and then stops, but after sitting for a while the system again produces cold air it sounds to me like the evaporator is freezing. Set the control to a reasonable temperature and see if it will stay on. When the evaporator freezes it is not possible for air to pass through it. once it defrosts then air can again flow. When the outside humidity is high and temp is low this can happen.

 

[Mike Pfeifer]

sounds like the evap freezing up.

 

[Mike Pfeifer]

If you are running it with the coldest setting and it produces cold air for a while and then stops, but after sitting for a while the system again produces cold air it sounds to me like the evaporator is freezing. Set the control to a reasonable temperature and see if it will stay on. When the evaporator freezes it is not possible for air to pass through it. once it defrosts then air can again flow. When the outside humidity is high and temp is low this can happen.

Ha, beat me to it!

 

[Drmklr]

Thanks all! Will try it out in the morning.

 

[sk47]

If you are running it with the coldest setting and it produces cold air for a while and then stops, but after sitting for a while the system again produces cold air it sounds to me like the evaporator is freezing. Set the control to a reasonable temperature and see if it will stay on. When the evaporator freezes it is not possible for air to pass through it. once it defrosts then air can again flow. When the outside humidity is high and temp is low this can happen.

Hello; good thought and suggestions. Best I recall also running higher fan speeds may help with evaporator freezing.
Don't know if i mentioned in this thread but later model cars often have a cabin air filter. If it is clogged up that can affect air flow. Needs to be cleaned or changed about once a year.

Sponsored