Overheating is the most common reason why engines get damaged. There are many reasons why your engine might be overhead and even more ways to diagnose the real problem.
In this article, we’re going to talk about specific situations of why cars overheat when the A/C is on.
Certain questions such as: “why does my jeep overheat when I turn the ac on?” or “please help me I cannot find the cause of the 2013 ford fiesta overheating when the ac is on” may pop up.
This can be frustrating, so when experiencing any of the following symptoms, you have to stop and take immediate action in order to limit any further damage to your vehicle.
Understanding AC Overheating
When you turn the air conditioning on, it will cycle refrigerant through the AC system, absorbing heat from the cabin that disperses into the environment.
The AC compressor is pivotal in this function, and it’s driven by the serpentine belt or AC belt, depending on your vehicle’s design. Under normal circumstances, there’s little to no effect on your engine temperature.
But if the temperature gauge goes up when the AC is on, something is amiss. The problem can often be isolated by turning off the AC and watching if the temperature begins to return to a more normal state.
You’ll typically find that this scenario happens:
- When the outside air temperature is extremely hot
- The vehicle hasn’t been properly maintained
- There’s a failure of some kind
Understanding what occurs with the engine when the AC is on can be beneficial to figuring out the cause of your overheating issue.
The cooling fans that draw air through the radiator also draw air through the AC condenser, removing heat and dissipating it into the atmosphere.
Symptoms of a car overheating when ac is on or idle?
Your car’s air conditioning system is working overtime to keep your vehicle cool this summer. If the AC unit goes out, you’re in for a truly miserable ride.
There are tell-tale signs that something may be wrong with your AC system, like trouble turning on or driving performance issues. These can also serve as warning signs before you an overheating AC unit occurs:
#1. Puddles of water under your car when parked.
Water leaks commonly occur around the condenser and evaporator drain hoses if this part of the AC system becomes damaged.
A leaking drain hose or fluid line should never take precedence over other vehicle maintenance concerns. However, an overheated air conditioner could be one result of neglecting these problems.
#2. Water dripping from the AC vents.
If you notice water dripping from your car’s air vents, the problem is likely that condensation has built up inside the system.
This can happen when there’s a leak or other drainage malfunction in the lines. Bugs and dirt could be blocking airflow somewhere in your AC system.
Replacing an old refrigerant may also solve moisture build-up issues. These are all coinciding possibilities that should be ruled out if your vehicle is experiencing this condition.
#3. Your Air Conditioning Unit Is Making Strange Noises.
Hissing, bubbling or rattling noises are probably bad news which indicates that something isn’t right with your air conditioning unit.
A hissing noise may mean you have dirty evaporator coils, while unnatural gurgling may mean there’s a leak in the system. There could also be a loose belt or another issue if your AC unit is making odd sounds.
#4. Your Air Conditioning Unit Is Ineffective On Very Hot Days.
If your vehicle cools inconsistently or isn’t as cool as it used to be, it may be that you need a refrigerant recharge. Low refrigerant levels can spell trouble for an air conditioner and leave you with a very expensive repair bill.
If this is the case, simply recharging your car’s AC will no longer work and full maintenance might need to take place.
This type of situation should always be handled right away; neglecting to address these signs could lead to an overheating AC unit that must be replaced completely.
#5. Your AC Unit Is Making Unusual Noises.
An air conditioner that makes rattling, knocking, or buzzing sounds may also indicate low refrigerant levels or another system malfunction. Take your vehicle into the shop ASAP if you hear any unusual noises coming from your car’s air conditioning unit.
Causes car overheats when it’s idle and the A/C is on?
Now that you’ve noticed the problem of overheating, what could be the cause? Well, we’re about to explain the possibilities.
#1. AC Compressor Overload.
It’s a fact that the compressor puts more load on the engine whenever the AC is on. Conduct a test by putting the AC on and observing the little boost in RPM (rotations/revolutions per minute).
Automobile makers try to ensure that car cooling systems won’t trigger any problems. However, issues start to come up when the compressor seizes, and the accessory belt stops it from turning.
The vehicle will keep trying to turn the compressor leading to the overheating of the engine as a result of added pressure.
#2. Problem With Radiator.
There can be blockages or interferences in the internal pipes of the radiator, which can negatively affect the flow of coolant and air in it, thereby causing overheating. It can be an accumulation of substances such as rust, dirt, and so on. Leakages may also be a factor.
#3. Faulty Fan.
Your car can overheat when the AC is on, and you’re stuck in traffic or driving slowly. The problem is triggered when the cooling fan (including the cooling motor, fan clutch, or any other component that makes the cooling fan work) has a defect.
For example, the fan moves at diverse speeds depending on the load needed to cool the engine (your car may have two fans). The motor won’t receive adequate cooling if the fan isn’t performing as powerfully as it should—leading to overheating.
Another instance is when there are blockages or interferences in the radiator. Such a situation can lead to the restricted passage of coolant through to the vehicle’s engine, damaging the fan switch.
Apart from the above scenarios, a faulty fan relay can also be a possible factor. It’s obvious that there’s a need to perform maintenance checks on the cooling fan regularly.
#4. Other Cooling System Issue.
Proceed to examine the other parts of the cooling system after you’ve checked the cooling fan and found nothing wrong with it.
The condenser converts cooling gas from its gaseous form to a liquefied state. It performs this primary role well as long as blockages don’t restrict the flow in the radiator.
We discussed the radiator earlier. You can see how it’s an important part of the system in the prevention of overheating.
Back to the condenser—it heats up when the AC is working. This is why there’s a need for a cooling system to keep the condenser’s temperature at an optimal level. The cooling system needs to be performing as well as it should at all times.
Overheating can also be caused by a faulty water pump when the AC is on. A malfunctioning water pump will give rise to inadequate heat depletion.
#5. Defective Engine Coolant Sensor.
The engine coolant sensor signals the control module to switch the cooling fans on, so this device may be the cause of your overheated car.
Why? It may not be signaling the control module correctly.
In case, after diagnosis, you still cannot find out the causes of this situation and things get even more complicated, you should scan for trouble codes related to your AC system using a quality diagnostic scan tool. Hopefully, it will help you discover the root of the issue.
How Do You Diagnose a Car That Overheats When Idling and AC on?
Diagnosing the car with the problem will help you determine the cause of the problem. Since the vehicle has a problem when the AC is active and idling, perform several experiments accordingly,
- Observe the engine temperature with AC off when idling and while on and driving. The experiment will help you determine the cause of overheating between the engine idling and the air conditioner.
- If the problems seem more on idling, check the fans and test them with your car’s battery.
- Also, check for leakages on the hose and use a block tester to check for air bubbles in the coolant.
- Observe the engine RPM when the air conditioner is active while the vehicle is moving and when stopped. If the RPM increases, the Ac compressor might be faulty.
It’s best to start your diagnosis with the cheapest solutions and advance to the more expensive ones. With this strategy, you’re less likely to waste money on the wrong repairs.
How to fix the problems?
Repairing an engine overheating due to a defective AC system may be a bit confusing because it involves many parts, but also it’s not that hard because once you solve the problem, it’s gone forever and you begin to enjoy your ride once again. Here are some fixes that might help you resolve your issues:
- First thing you should test the fan and auxiliary fan (if equipped). And test if it works at full speed when the AC is on. If the fan motor is in good condition, try checking the relay that is responsible for the AC fan.
- Check the radiator for any clogs and obstacles that can block the flow. Additionally, try to get the radiator out every now and then and check it for leakage as well as clean the internal pipes with special tools and substances that dissolve any dirt and rust that may cause blockages.
- Check the water pump for erosion on the internal fins. Damaged water pumps could cause serious problems to the engine by causing it to overheat.
- To avoid any rust or corrosion in the radiator, water pump, or even the internal engine parts, you should change the coolant every 40.000 km or 2 years with a recommended type; and concentration, and always avoid using tap water as it contains salts and corrosion causing substances.
- If your car is overheating after adding Freon gas, it may mean that the type of this gas Freon used is not compatible with your compressor. This can put a huge load on the compressor that may lead to damage to the A/C compressor. In the worst-case scenario, it may lead to your car overheating when A/C is on. The compressor would overheat and would blow hot air through your vents as opposed to cool air.
What to Do If a Car Overheats With the AC On in Traffic?
This could be a real bummer. Aaargh! Still, try to keep calm and follow the steps below.
Step 1: Pull Over as Soon as Possible.
This is the very first step that you should take. Ensure that the conditions are right before doing so. Remember, safety first.
Step 2: Turn Off the Air Conditioner.
This should be done immediately, especially when you realize that there’s no chance to pull over. Confirm that it’s safe to set the vehicle in park or neutral when you have to wait for a stoplight. It’s a way to reduce the temperature of the engine a little.
Step 3: Open the Hood of Your Car.
As stated earlier, safety first. Be sure that it’s OK to do this because of the temperature of the hood. Therefore, play safe by checking to see if steam is escaping from under it. If so, be patient for a while. Opening the hood will greatly reduce the temperature of the engine.
Step 4: Turn Off the Car Engine But Keep the Key in the ON Position.
Set the vehicle on park and put off the engine if you’re able to pull over successfully. The fan will continue running (in some car models) as long as you leave the key in the ON position.
Substitute the fan with a new one if you discover that it isn’t on. This could also mean that it’s linked to the overheating problem.
Step 5: Check for Leaks.
Once the engine has cooled down, proceed to check for leaks and/or call an expert for help. Patch up any leaks you find with radiator hose tape or by tightening a clamp.
Fill up the radiator with coolant and water after. The expert you called should do a complete check to discover everything that went wrong with the engine.
Effective Solutions to Prevent Overheating
#1. Regular Coolant Checks and Flushing.
Keeping the coolant at the proper level and flushing the system regularly ensures optimal performance and prevents blockages that can lead to overheating.
#2. Regular Inspection and Cleaning of Radiator and Condenser.
Ensure the radiator and condenser are clean and free from blockages. Regular cleaning can improve cooling efficiency and prevent overheating. I have recently shared the importance of perfect condition condensers when your car AC isn’t blowing cold air.
#3. Repairing or Replacing Faulty Parts.
Timely repair or replacement of malfunctioning parts such as the water pump, radiator fan, and thermostat can prevent more extensive and expensive issues later.
#4. Regular Belt Inspections.
Check belts for wear and replace them if they appear damaged. Properly functioning belts ensure the efficient operation of cooling and AC systems.
Preventive Maintenance Tips
- Schedule regular servicing of your car’s cooling system and AC.
- Keep coolant levels in check and inspect for leaks.
- Clean the radiator and condenser to prevent blockages.
- Visit a trusted repair shop like Urb’s Garage for routine checks to avoid sudden breakdowns and overheating.
FAQs.
Q: Can a low refrigerant level cause the engine to overheat?
Not directly, but a low refrigerant level can cause the AC compressor to work inefficiently or cycle excessively.
This increases strain on the engine, which can contribute to overheating if the cooling system isn’t in peak condition.
Q: Should I replace my thermostat if my car overheats when the AC is on?
Possibly. A stuck-closed thermostat can restrict coolant flow, causing overheating, especially when extra heat from the AC is added.
If your car consistently overheats, checking or replacing the thermostat might help.
Q: Why does my engine smell like burning when it overheats with the AC on?
A burning smell could indicate leaking coolant hitting hot engine parts, an overheating serpentine belt, or an AC compressor that’s failing under load.
Q: Can extreme humidity make my car overheat faster when using the AC?
Yes, high humidity can make the AC system work harder to remove moisture from the air, increasing the load on the engine and potentially causing overheating if the cooling system is weak.
Final Words
We recommend that you always check your cooling system as part of your periodic maintenance. This will prevent you from having bigger problems down the road.
The engine’s first enemy is heating because it can damage the internal parts. This guide should help you fix the problem, but if you feel confused even a little, you should have an expert look at it.