Warning Signs
Older cars won't have a warning light specifically for the air conditioning. Many newer vehicles that can display much more detailed information will be able to tell you if there's an issue detected.
There are many universal signs that your AC is experiencing a problem, though. This can include weak airflow, a failure to produce cold air for very long, or particular smells that hint of mold or mildew. Let's explain each:
Weak Airflow
There can be a number of causes of weak airflow in your car's air conditioning. The simplest is when a hose comes loose. All it takes is reconnecting the hose that supplies air to the blower. That's fast and simple.
Other causes can include a bad ventilation fan. If it's stopped working, it's not blowing air through the unit properly and will need replacement.
You could also have a mold or mildew problem. The evaporator core can trap moisture as the air conditioner is operating. Moisture, of course, can breed mold or mildew, blocking efficient air movement.
Another cause may be that some of your seals have broken or deteriorated. Busted seals can mean that cool air is escaping rather than being blown into the car or that the evaporator core can't work efficiently. This is a more complicated scenario and can mean the AC system needs replacement.
Nasty Odors
This is one of the simpler problems to confront. The most likely cause of a nasty odor is a spilled drink in your car, so always take a look under your seats to make sure the cause isn't something else.
If it's definitely coming out of your AC system, then the likely culprit is a cabin air filter that needs replacement. These air filters help keep dust and debris out of the AC system and the cabin, but they can break down. This is a very inexpensive component to replace, and it's done quickly.
The other cause can be an evaporator case that's developed mold. The case has a drain, but if it becomes clogged or obstructed, mold will usually follow.
Not Producing Cold Air
Your car's air conditioning system can fail to produce much cool air. This defeats the whole purpose of having AC in your car. Some of the causes are simple, such as a clogged refrigerant charging hose or a failed switch or fuse.
Your system may have developed a leak. Sometimes leaks are connected to and cause other problems, so often a more complex mechanical issue will be found in conjunction with a leak.
More complicated issues include a Freon leak from a deteriorated hose, o-ring, or seal. The compressor or motor could have mechanical issues that impact the whole system. Same goes if the condenser or evaporator have failed.
Blowing Hot Air
Sometimes your system will begin by blowing cold air but will quickly taper off into blowing hot air. This tells you that your system needs an inspection immediately.
The simplest cause of this is a blown fuse. All it means is that the unit isn't getting the power it should. This is a simple issue to solve.
Another simple cause may be a clogged expansion valve. This is what supplies refrigerant in a balanced amount to the evaporator. If this valve has a clog, the evaporator can't get refrigerant. Leave this issue too long and moisture collection can cause the backup of refrigerant to completely freeze the valve.
A common issue is a broken compressor clutch. This simply means that the compressor isn't being engaged. You won't have the right pressure in your compressor, so can't get any cool air.
Once again, leaks can also be the culprit. Leaks and blown seals keep showing up because they're connected to so many AC issues. It's worth it to talk about leaks in their own section:
A Word on Leaks
Leaks can be minor if they're caught early enough, but there's one rule that holds true for all leaks: if you don't address them, they will get worse.
This doesn't just mean the leak itself will get worse. Don't wave off a leak. Leaks can allow too much moisture into your AC system, and that means more extensive damage to more expensive parts. It's always worth it to get a simple leak repaired today rather than wait and have to replace your entire AC unit in a few months.
Some leaks can cause moisture to mix with refrigerant. This can cause parts to freeze, such as the clogged expansion valve covered above.
Leaks are often (but not always) caused by moisture in your system mixing with refrigerants. This results in corrosive acid that will eat through parts of the system, including seals. This causes a cascading cycle: moisture enters the system, causes a leak, which creates corrosive acid that eats through seals, causing more leaks, allowing more moisture into the system, causing more leaks, and so on. That's why even minor leaks in an AC system need to be addressed quickly. They're most common in older AC systems where rubber elements have become more rigid.
How an AC Leak is Found
When mechanics or technicians test for leaks, they can use refrigerants with dyes that show up under a black light and bring in a special device nicknamed a “sniffer” that detects refrigerant. Either of these strategies can quickly make a leak's presence and location apparent. From there, it's easy to come up with a plan for how to fix the issue.
It's easy and quick to have your AC unit tested for leaks. This is one of the best ways to avoid more complex and more expensive problems with your car's AC.
Stay cool this summer! Bring your vehicle to RetroLube when your air conditioning is on the fritz.