The air conditioner system in your vehicle is designed to keep you cool. For this reason, it is a pretty good indication that something is wrong if it starts blowing hot air. Unfortunately, this fault in your air conditioning system could be the result of a few different problems.
Does the Compressor Engage?
The first problem you can check is whether the compressor is working. You'll be able to see this by checking if it engages. For it to engage, it also likely has enough refrigerant to work, so the problem is within the actual unit inside your car.
When the compressor doesn't engage, you'll need to check for where the problem is within this part of the system. Try connecting the compressor clutch to the battery to see if that is at fault. If it works, there is a problem somewhere along the electrical system. You could need a new pressure switch, compressor clutch relay or clutch cycling switch.
If your compressor clutch works connected to the battery but there is no cold air, it is likely that your refrigerant is running low.
Is Your Refrigerant Leaking?
Just topping the refrigerant isn't necessarily going to be enough. You need to figure out why there isn't enough refrigerant, and in most cases it means you have a leak. Allowing the leak to continue could damage other parts of your vehicle, as the leak will mean the refrigerant evaporates around the car.
Unfortunately, a refrigerant leak is less obvious than other fluids. This means you will not necessarily have puddles under your vehicle. Most people do not realize they have a leak until they check the fluid and realize it is low. The leak could be in the evaporator, condenser, or compressor. Professionals, such as at Williams Oil Filter Service Co., use UV dyes and a test kit to find the leak because of how difficult it can be to track down.
Is There Pressure in the System?
A refrigerant leak can also lead to pressure changing within the system. You'll be able to check the gauge, to see if it tells you whether it is high or low. Most of the time, refrigerant leaks lead to extra pressure in the system. You will need to get this out before topping up the refrigerant levels, or hot air will continue to blow and you will damage your HVAC system.
Are There Blockages?
When you know you have the refrigerant levels right and there is no excess pressure, it's time to look for blockages. These could occur anywhere in the system, and will prevent the refrigerant getting around the HVAC unit to allow cool air to blow through. Just like a leak, the blockages can occur in a lot of different areas of the AC system. This means it is best to turn to an expert to locate and fix the blockage.
Not having air conditioning in your vehicle isn't really a problem that needs fixed immediately as the vehicle will still operate without air. It, however, will make the vehicle extremely uncomfortable to drive in the summer and can make it more prone to overheating.