I need to give everyone a heads up and what to be aware of. I purchased my 2011 Mustang new in June of 2010. Immediately I noticed that once in a while the air conditioner would blow warm air. It would last only a few seconds and then go back to cold where it usually stayed. This summer the air started blowing warm as often as cold. The hotter the ambient temperature the hotter and longer it would blow. At 90 degrees outside temp it had a swing in air conditioning temp of 15 degrees. At 100 degrees the temp differential was more than 15 degrees and would blow hot air more than cold. I have had the car in 5 times now. Ford engineers got involved and they just notified me that they consider this temp differential to be within normal limits. Thats BS as I have purchased 5 new fords over the years and none of them had this trait. The dealership drove three new mustangs they had on the lot and couldn't get any of them to do this. My Fusion 4 banger loaner car does not have any temp differential. Ford has tested and re tested all the components and cannot figure out how to fix it. Ford has told me to pick up my car and they will not address the issue anymore. I was hoping it would not come to this as I have a few hundred in aftermarket improvements in the car but I am in contact with a lemon law lawyer as I feel it is my last option. What a shame! Hope no one else has to go through this but if you notice a temp differential in you air conditioning expect it to get worse with no fix from Ford.

 

Actually, I have to say I have experienced this somewhat this summer. I wouldn't say it gets to blowing hot air, but it's noticeable that cold air stopped flowing like the condenser wasn't working, or the belt was slipping or something odd..

The solution (maybe this helps figure out the problem) for me, was to also click the cycle air button, so instead of slamming the AC with work to continually cool new 'fresh' 95degree+ air, it's only working to cool the already cooled, cycled cabin air.

Now I'm back to freezing my butt off - you might want to check this. Given it's the dead of summer - use that cycle cabin air button?

Maybe your car is having an issue with those vents opening/closing properly? (Sorry not an A/C guy if that doesn't make sense in relation to our cars)

 

I'm sure you have been told this by the dealer but the compressor does cycle on and off to prevent icing which might cause tha air temp to go up and down. As stated above, I also always use the AC with the cabin air on recycle on so it's not working so hard to cool direct outside air.

 

I too am disappointed with the performance of my 5.0's ac system as it takes much longer to cool down my car in the summer than the 2000 or 2003 gt's ac. Anyone know what the specs are for say temperature drop on high fan setting for outside air temp to inside air temp at say above 1,500 rpm engine speed? 50 F drop?

On a 90 F day with ac on full using outside air cruising at 60 mph after 30 minutes the cabin is still not cool and the air coming out the ducts seems to be about 60F. Under the same conditions with the recirculation air setting it takes 15 minutes to cool down the interior. Dealer indicated it all works properly! To me it seems like the system is only 70% charged!

To the original poster perhaps there is something wrong with the air diverter damper in the heater/cooler box not seating properly?

 

We've been having record breaking temps here, over 100 on a few days with high humidity. My AC has been fine. If yours is not keeping up, sounds like it may have a problem.

 

While we're ranting about AC, Why the F is there not an auto button for it. Its the thing I miss the most on my 2000 accord.

 

My dealer has tested all components of the hvac system multiple times. They even disconnected the blend door to rule out a partially open door that could allow this to happen. By their testing it will blow between 45-60 degrees when ambient temp is 90. When it is 100 out the differential is even greater but they would not share the test info with me. My local dealer has been great on this but ford engineering is calling all the shots. The dealer service people drove three new mustangs they had on the lot and none of them would do this. I drove a fusion for 10 days and the little four banger would not cycle like this car does.
mmdpg- yes the compressor must cycle to keep condensation from freezing up the system but this should show minimal temp change at the registers. My dealers service manager and 3 techs that worked on this car all have told me they would not consider this acceptable if the vehicle was theirs. I purchased this car new in June of 2010. Once in a great while it would blow warm air and then just for a couple of seconds and then it would work well the rest of the trip. Now it is to the point it will blow warm air as much as cold and it will not cool the car if it is over 100 degrees outside. The condition is getting worse and I am afraid it will eventially quit and I will have no air conditioning- and ford cant figure out how to fix it.
I am currently in touch with a lemon law lawyer on what can be done. Too bad it has come to this as this car is fantastic in every other way and I hate to have to give it up.

 

Interesting and thank you for such an informative post. I am surprised Ford can't do any data logging (set sensors on critical items not already monitored by the cars computer) so when the issue arises they will know where to look for a solution. Good luck and thank goodness for the lemon law!