S550 Mustang HVAC System Overview

The evaporator core found in early production S550 Mustangs has been taking a lot of heat, but for all the wrong reasons. Many 2015-2016 S550 owners have reported a vastly premature failure of the evaporator core, resulting in an air conditioning system that cools the cabin erratically – if at all – and systematically coats the inner windshield with a white film. As much as I wish the path to superhuman strength be this easy, it is doubtful that breathing R-134A refrigerant will bestow upon you any sort of superpower, thus it is best to get this issue taken care of promptly if you suspect any sort of issue. Thankfully, this is a warranty eligible repair and due to the number of failures, Ford is very aware of this problem and is now keeping replacement evaporating cores in stock.

It seems Ford has been using an evaporator core with a revised part number for 2017 and later Mustangs, a hopeful indication that the early production core fault has been determined and subsequently fixed. Buried deep behind the dash in conjunction with the heater core, it is a bear of a job to do this yourself. Work smarter, not harder – if you suspect your Mustang is suffering from a faulty evap core, let the dealer take care of it.

Apart from the above mentioned exciting chance of becoming an unworldly mutant, the S550 Mustang’s air conditioning system is very safe and effective. A belt driven compressor uses an electric clutch to engage and disengage the system, using the more environmentally friendly R-134A cooling agent as its choice freon. Having spent several days with an A/C equipped 2016 GT in Vegas, the system was more than capable of keeping the cabin cool and comfortable in the August heat without even needing to have it set to full blast.

Premium level S550 Mustangs will also benefit from dual-zone climate control (meaning both driver and passenger can set a different temperature) and can even come with cooled seats (200A, 400A package). These seats use built-in electric fans, strategically placed, to blow interior air around the seat bottom, back and lumbar area. It’s a nifty feature that more or less eliminates that momentary grotesque feeling of your t-shirt peeling off the seatback as you step out of the car, which realistically, is probably a must-have in hotter climates when going out on a date.

Now, if your Mustang does not have any air conditioning at all (although I believe in this day and age it is very tough to order a regular EcoBoost or GT sans air climatisé), Ford Performance does offer a package with the compressor, lines, and all the necessary plumbing.

Believe it or not, some 2015 and later Mustangs do operate in colder climates. In fact, some 2015 and later Mustangs operate in colder climates all year round. It may be tough to keep the front pointed in the direction of intended travel when mucking about in several inches of snow, but at least you’ll be warm as you battle with traction control.

The S550 Mustang uses a conventional heater core system to provide cabin heat and defrost.  Once the thermostat has opened and is circulating warm coolant, it is routed through the heater core which is basically a miniature radiator. When you cycle on the blower with the temperature knob on the hot side, heat is transferred from the coolant in the heater core to the air as the air passes over the fins of the core. The heated air is then routed to the cabin vents. It’s a basic system that works well and is essentially the system every mass production vehicle uses today.

Intended more or less as a lifetime component, the heater core is housed behind the dash (alongside the evaporator core), making it a real PITA to change if it develops a leak or becomes plugged. While the former issue cannot really be prevented (everything breaks down with age), the latter certainly can by routinely flushing out the cooling system and replacing the old coolant with a fresh batch, as outlined by the owner’s manual.

If your Mustang is only producing a limited amount of heat, or no heat at all, this could be due to a faulty thermostat. The factory thermostat found on 5.0L Coyote engines is set to open at 190 Fahrenheit and 180 F for 2.3L EcoBoost Mustangs. Performance branded thermostats exist on the aftermarket that open at a lower temperature in order to help keep engine temperatures lower, and thereby maintain better performance. For Mustangs in very hot climates, these types of thermostats may have a benefit. However, for an S550 Mustang operated in a more northerly climate, such a thermostat will keep the engine too cool.

Matching the air cooled seats of a premium package ‘Stang, electrically heat seats are included in order to keep your buns warm and in form when the temperature drops.

By and large, the god particle of the S550 Mustang HVAC system has got to be the cabin filter. Responsible for filtering all the air that enters the cabin through the HVAC system, the cabin filter plays a dominant role in air quality and air odor. Surely often overlooked, the cabin filter really ought to be replaced every year in order to ensure clean and odor free air continues to come out of the vents whenever the HVAC system is in use. Easy to access underneath the passenger side dash, all it takes is one torx  driver (size 20) to undo the cover and then you can use your hand to pull the filter out.