Keeping your car’s air conditioning system in a decent state of repair is essential if you want to avoid sweltering on hot journeys. Even in places like the UK, cabin temperatures can skyrocket in direct sunlight.
However, AC isn't just about keeping you cool. Many mechanics (like us) also view it as a safety feature. Unlike conventional airflow through vents, it takes moisture out of the air entering the car, reducing windscreen fogging and helping you keep your eyes on the road. It also keeps you cool and reduces driver fatigue (which is a problem when it gets too hot), so you can concentrate on long journeys.
The purpose of this guide is to give you an understanding of your car’s air-conditioning system, what can go wrong, and how to fix problems when you encounter them. By the end, you should have a better idea of what you can do to maintain your vehicle’s AC unit, and when it might need replacing.
Vehicle Air Conditioning: How Does It Work?
Air conditioning seems like magic when you first encounter it, but there’s real science behind it. Systems in vehicles are essentially the same as those in houses, although on a smaller scale.
Air conditioning begins at the compressor. This piece of equipment forces the refrigerant into a smaller volume, increasing the temperature and density of the gas.
The condenser comes next. This unit takes heat from the refrigerant and releases it to the external environment, usually with the help of a fan or the vehicle’s motion. This action produces the condensation phase (hence the name “condenser”), reducing the temperature of the coolant by transforming it from a gas to a liquid as it loses heat.
As the liquid cools, the system pumps it back into the AC system. Then, when it comes into contact with warm air, heat exchange occurs, and it becomes a gas again, restarting the process.
All these stages rely on every component working. Any problems with the coolant, compressor, condenser, fan, evaporator, or expansion valves can stop the unit from functioning. Sometimes, even the belts that drive the system can break, leading to issues.
Common Air Conditioning Issues And How To Fix Them
Most air conditioning units in new vehicles last a long time. However, as they age past five years, things can go wrong.
In this section, we explore some of the issues that you might encounter, especially if your AC unit is getting older. These problems are more common than you might imagine, (which is why we see all of them repeatedly in the workshop).
No Airflow
Weak or non-existent airflow from your air conditioning unit is a common issue and can indicate several problems. Usually, the cause is a faulty blower motor (which is a quick fix), but you could also have blocked vents.
We fix this issue by:
- Replacing the blower motor with one that works
- Cleaning out any obstructions from the pipes leading to the blowers
- Replacing the filters to enable smoother air flow
Unusual Noises
Another sign you may have an issue with your AC unit is unusual noises. Loose components, broken belts, or debris in the system can cause it to malfunction.
Again, strange noises can have multiple causes, so we always perform a full diagnostic. Inspecting the system reveals which components are faulty for a quick replacement.
We can deal with unusual noises by:
- Tightening up loose components and preventing rattling
- Checking the compressor for wear on the moving parts
- Cleaning the system and removing any grime buildup
Failure To Cool Air
You can also encounter situations where air is coming through the vents, but it isn’t cool. This usually happens if you have low refrigerant levels or a malfunctioning compressor.
We fix this problem by:
- Topping up the refrigerant levels in your system
- Dealing with any leaks
- Fixing or replacing the compressor if there is damage or it can no longer function
Bad Smells
Finally, you might have an issue with your air conditioning system if it is producing foul odours. Usually, systems should be odour-free, but you may have dirty filters or bacteria growing in the evaporator. This smell is worst when you first switch on your system and then improves over time.
Obviously, this issue is a health risk, especially for people with weakened immune systems. Therefore, we fix it by:
- Cleaning out your AC with disinfectant
- Replacing cabin air filters
- Sealing gaps where moisture and bacteria could enter
If you notice any of these issues, deal with them early. The longer you leave problems festering, the more damage they cause, and the costlier the final repair bill will be.
DIY Vehicle Air Conditioning Maintenance
We recommend you bring your vehicle to us for regular air conditioning services. However, there are some DIY tasks you can do at home.
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Perform Regular Checks
For example, we suggest you perform regular checks on your air conditioning system, at least once a quarter. Look out for all the signs discussed above, like strange noises or bad smells.. Also, open your bonnet and inspect the belts and hoses for wear. Any damage is usually obvious.
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Clean The System
Also, clean the system regularly by changing the filters every 12 months or so. Keeping them fresh prevents gunk buildup and stops the system from smelling and degrading from within. Learning how to do this is quite easy and doesn’t require any specialist knowledge or tools.
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Run The System During The Winter
Lastly, it’s a good idea to run the system during the winter, even if you don’t need cooling. Getting the system going lubricates internal components and keeps them healthy while you wait for more frequent use during summer months.
Professional AC Maintenance And Repair: What’s Involved?
Sometimes, casual DIY AC repairs aren’t possible. While some fixes are easy, most air conditioning systems inside vehicles break down in complex ways.
Fortunately, we have the tools and knowledge to fix these problems. Our goal is to get your AC unit up and running again so you can enjoy rides in your vehicle on hot days and defog your windscreen in the morning.
Replacing The Refrigerant
Replacing the refrigerant is a professional AC servicing option we offer. Work starts by turning off the AC system and ensuring we power down the unit to prevent damage. Then, we gather the equipment we need, like the vacuum pump and gauges before connecting the unit to the recovery machine.
The replacement begins by removing the old refrigerant. We do this carefully by capturing the gases in containers instead of allowing them to be released into the atmosphere.
The next step is to inspect the system. This step avoids a situation where we remove the old refrigerant, only for the replacement fluid to leak out again once you hit the road. Our mechanics repair things like damaged hoses and split O-rings, ensuring the coolant remains inside the unit when you drive away.
Next, we attach a vacuum pump to the AC via the manifold gauge set and remove air and moisture. This process lasts 15 to 30 minutes, reducing the risk of contaminants harming your AC in the future.
Finally, we charge the system with a new refrigerant, using a formulation designed for your components. The coolant comes from a canister and travels through the manifold gauge to the service ports. We add just the right amount for optimal performance, matching your system’s specifications. The last step is to disconnect all the tools and ensure that the AC system cools the cabin without any strange noises or performance issues.
R-12 was the old coolant used in vehicles, but it is now banned due to its effects on ozone depletion. These days, R-134a is used in older vehicles, and newer cars use safer R-1234yf.
Repairing A Damaged Compressor
Our team can also help you fix a damaged or broken compressor. Problems with this unit can prevent the AC system from working at all, so fixing it is essential. Consequences can include warning lights on your dashboard, refrigerant leaks, strange noises, or warm air coming through your vents.
We fix compressors by removing the coolant, taking the compressor out of its compartment and identifying the issue affecting it. This step involves unplugging various connectors, disconnecting the clutch and sensors, and allowing the tensioner belt to loosen and slip off.
Sometimes, debris inside the compressor can cause problems, so we flush the system if needed. We also inspect all the O-rings on the unit for damage and replace them if cracked or fatigued. Occasionally, these minor repairs are all that’s needed, in which case, we reinstall the existing compressor and test the system.
For more extensive damage, we replace the old compressor with a new one. We do this by mounting the new unit in the correct position and tightening the bolts to specification. Then, we reattach hoses and lines, connecting new O-rings where necessary. After that, we adjust the belt tension and plug in the clutch and sensors.
Once vacuuming and recharging are complete, it’s time to test the unit. Usually, replacing the compressor is all we need to do, unless we find issues in other parts of the system.
Repairing Or Replacing The Condenser
Lastly, we can help you with condenser repairs and replacements. These are necessary when the unit isn’t cooling or you notice strange noises whenever you turn on your AC system.
The first step is to remove the refrigerant by connecting the recovery machine to the AC service ports. Once the system pressure is at zero, we disconnect the battery and other components from the compressor and lift it from its mounting.
The next step is to prepare the system. We check for things like debris or metal shavings in the lines, and flush out the system if we find any contamination inside.
As with the condenser, these simple fixes sometimes work. However, you may require full compressor replacement (installing a new unit) with more extensive damage.
Once the refrigerant lines and drive belt are in place again, the new system is ready for evacuation. First, we attach the pump and connect it to the manifold gauge set and then run it as before, testing the internal vacuum holds before recharging the system. Lastly, we do a final inspection to check for leaks using a UV dye. This confirms the system is sealed before it hits the road.
The Environmental Impact Of Car Air Conditioning
The environmental impact of car air conditioning is less than it used to be due to improved emissions and refrigerant standards. However, it is still a concern for some vehicle owners.
Fortunately, following a few basic practices can reduce concerns. These include:
- Parking your vehicle in the shade, such as under a tree, in a garage, or a covered car park
- Using your AC more efficiently, including fully ventilating the vehicle before switching it on
- Only going to workshops offering the safest refrigerants for your vehicle
- Traveling less on hot days
When To Call The Professionals For Air Conditioning Repair, Maintenance, And Installations
Sometimes, you can’t fix your car’s air conditioning yourself because you don’t have the tools or the knowledge.
Fortunately, we can help, even if you are dealing with persistent issues. Our team gets to the bottom of problems with your AC unit so you can enjoy yourself more on the road.
The benefits of a specialist service are substantial. With us you get:
- Deep expertise on what can go wrong with vehicle AC units and how to fix them
- Access to specialised tools that can resolve complex problems, like refrigerant issues
- Repairs that foster long-term reliability instead of papering over issues
Ultimately, we’re here to help if you have any issues with your vehicle’s air conditioning system. Our team understands the job and what we need to do to give you a better driving experience.
