Why does my air conditioner stop cooling when the car is on idle or at a stop in a traffic light?
My mechanic recently informed me that my car air conditioner compressor was faulty, and it was subsequently replaced. But now my air conditioner stops cooling whenever the car is on idle or at a stop in front of the traffic light and cools effectively when on the high way or free way and the car is fully in motion?
My car has 120000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
Hello. Was the A/C working properly before you had the condenser replaced? Your previous mechanic was correct that the condenser was likely the source of the issues. Now that the condenser has been replaced, we know its working and can tell its the cooling fan that is failing to provide adequate air flow. You should turn your attention to the fans. They can fail in several ways including the fan clutch, fuse, and its main control module. You may also want to verify that the connections are clean, dry, and tight. The first step is to check and see if the fans are working at all, or if they have not been working this whole time. If the fan is not working at all, it or its motor should be replaced. If the fan is working intermittently then there will need to be more testing to determine what is causing it to only respond to certain signals.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
When the compressor is not functional, it finds it difficult to get cold, and the engine should put extra work into it to make it cooler. Therefore, when the car is not moving, the engine doesn`t work.
The coils cool down the air going into the cabin. If the compressor isn`t cold, your engine needs to work harder to keep those coils cool. When your car is stopped, your engine isn`t working—so the coils aren`t being cooled, and neither is the cabin.
If your A/C flip-flops from hot to cold and back again, your expansion valve could be failing. The expansion valve removes pressure from liquid refrigerant to allow expansion from a liquid to a vapor state in the evaporator. If the valve is blocked, the refrigerant flow could be restricted or could be too unrestricted.
The 5 reasons why car AC is not blowing cold air when idle are: low refrigerant levels, broken condenser fan, damaged condenser parts, overheating engine, and blocked condenser.
There are several things that can cause electrical problems for your car`s air conditioning. These can include failed switches, a blown fuse, a problem with the control module or something else. Fuses can short out and make the A/C stop working or a loose connection can create an electrical short that is easily fixed.
AC Works Intermittently: When the air goes from cool to warm to cool again, you`re experiencing intermittent problems. This is often due to a clog in the system, a failed compressor or compressor clutch, a faulty condenser fan, a clog in the system, or the actuator directing airflow has failed.
Symptoms of a Failing Expansion Valve
If the valve fails or has an issue, it can disturb the performance of the AC system, causing it to underperform. The AC system may begin to blow noticeably less cold than before and may even begin to blow warm air, depending on the severity of the problem.
So, as you can see, the problem of your AC only working when driving and blowing warm air when stopped can occur due to several reasons, such as inadequate cooling fan, slower refrigerant flow, clogging, and more. Also, the cost of repairs varies widely on the root cause of the issue.
You cannot run the AC without the engine running. The air conditioner compressor and clutch are operated by the serpentine belt that runs your other accessories (your alternator, for instance). If the engine isn`t running, then the belt isn`t turning. That means your air conditioner`s not actually on.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Why does my air conditioner stop cooling when the car is on idle or at a stop in a traffic light?
ANSWER : Hello. Was the A/C working properly before you had the condenser replaced? Your previous mechanic was correct that the condenser was likely the source of the issues. Now that the condenser has been replaced, we know its working and can tell its the cooling fan that is failing to provide adequate air flow. You should turn your attention to the fans. They can fail in several ways including the fan clutch, fuse, and its main control module. You may also want to verify that the connections are clean, dry, and tight. The first step is to check and see if the fans are working at all, or if they have not been working this whole time. If the fan is not working at all, it or its motor should be replaced. If the fan is working intermittently then there will need to be more testing to determine what is causing it to only respond to certain signals.
When idling, car overheats and A/C blows hot air – 2001 Saturn L100
ANSWER : Hello. The most likely cause of the issue that your are having would be a faulty cooling fan. The cooling fans purpose is to keep the radiator and condenser for the air conditioning cool during the idling function of the vehicle.
If the cooling fan is not working, this will cause the radiator and condenser to get very hot. When the radiator and condenser get hot, this can cause the vehicle to overheat and the air conditioning not to work. When the vehicle is driving at higher speeds, the force of air that is created towards the vehicle will flow through the radiator and condenser and therefore keep them cool. I would recommend having the cooling fan checked to make sure that it is working properly. If not, I would recommend having the cooling fan replaced.
Low coolant light comes on when AC, defrost or heater is on, but only if the car is in gear and stopped, what’s wrong with my car?
ANSWER : First, you want to make sure your cooling system is full. Check the radiator not the coolant jug. And check it when it is cold. If it needs coolant, add some. Of course, I don’t feel this problem is an actual low coolant condition. I would expect to find an electrical failure in the instrument cluster or from a component or wiring harness that is connected to the instrument cluster.
As a technician, I have access to reports from technicians across the country. I could not find any reports of this problem, so diagnosing this will require an experienced tech as this is not a common problem. In addition, this happens at intermittent times making it difficult to recreate. The most challenging part of this diagnosis will be recreating the symptom. I suspect it has something to do with the brake switch circuitry because it only seems to happen when you have your foot on the brake. I would begin my diagnosis there with a wiring diagram and test light in hand. The brake switch, instrument cluster, and environmental controls all interact with each other. Something is crossed either because of a failed module or damaged wiring in a harness.
Aside from making sure the coolant is full, this will not likely leave you on the side of the road. If you take it in to be diagnosed, be prepared for them to spend more time than usual to figure it out. Since it isn’t a key problem, you may need to live with it until it completely fails making it much easier to diagnose. Either way, I do recommend having a certified mechanic diagnose the warning light to make sure there isn’t anything serious going on.
Good luck.
My car has a rough idle when I start my car, when I stop at a light my car turns off. Is it the purge sensor?
ANSWER : This may be a result of a dirty or failing idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. Since this valve is controlled by the vehicle’s computer, it will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and repair your idle air control valve.
When I stop at the stop light or a stop sign my car shuts off.
ANSWER : It sounds like you may have a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.
Battery and oil light come on when trying to start car, take keys out try again car starts no problem and lights go away
ANSWER : Of course, don’t switch gears without being fully stopped, unless your Owner’s Manual or the manufacturer has alternative advice. However, the gear shift issue has no relation to the no-start problem you are describing. Inasmuch as you only have 6,000 miles on the car, the "constant on and off" that you believe has occurred is meaningless in comparison to the expected total vehicle service life. That is, assume what you perceive as "constant on and off", during merely 6,000 miles, might be equivalent to using the car "normally" for three years. A new car should be trouble free for at least 5 years, unless there is a defect, so your "constant on and off" is not a causal factor for any fault on the vehicle. What you might have is a defect in the ignition switch, or perhaps the immobilizer system, but if the problem is not in the switch itself, clearly there is an electrical problem.
If your vehicle is under warranty, by law the dealer MUST repair the issue you are describing within a prescribed time frame and number of "attempts", otherwise the dealer will run afoul of Federal and state Lemon Laws that give you very specific rights, and recourse (contact an Attorney; we are Mechanics, NOT attorneys). Consequently, if the vehicle is still under warranty, to save yourself money do be sure to seek a resolution from the dealer. If the vehicle is not under warranty, obviously a certified Mechanic from YourMechanic could identify the electrical fault and resolve this for you. If you want to go that route, please simply request a no start diagnostic -electrical system and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
I want to know how to tell of a fuel pump has gone bad, my car shit down on me while stopped at a light. My car has no CEL light?
ANSWER : Hi there. The best way to diagnose if you have a fuel pump problem is to listen carefully when you turn the key past the accessory setting. If you turn the key forward, but not all the way, you should hear a buzzing sound towards the rear of your car. This is the fuel pump priming the fuel lines. However, if your having difficulty starting your Mazda, it could be other fuel system components or ignition parts that are the root source of your issue. Due to this fact, it’s best to have a professional mobile mechanic complete a car is hard to start inspection at your location; so they can pinpoint the source of your hard starting issue and recommend repairs that will resolve the problem.
My car runs for about 30 minutes then when I come to a stop the oil and battery light turned on and car shuts off what could it be
ANSWER : Hi There,
It is normal for the oil and battery lights to come on when the car stalls. When the engine is not running and the key is in the ON position, you will see these lights light up as the car’s computer prepares itself to operate by running through a series of checks. The stalling and then re-starting after the vehicle has a chance to cool is likely related to a faulty ignition coil. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted repeatedly. The insulation develops small fractures that open when heated and close when cooled. When open, they allow shorting of coil windings and decrease or eliminate the coil’s ability to function. This type of temperature cycling happens because every time you shut the engine off, the fan stops running, the coolant stops flowing and the temperature under the hood rises. Every time you start the engine again the coolant flows, the fans turn on, and the temperature drops. When this heat dissipates and is absorbed under the hood, it is trapped causing this cycling effect. Other components that contain heat sensitive materials include parts like fuel injectors, igniters, and some sensors. Any of these may be potentially subject to this same kind of heat cycling problem which can be very difficult to trace. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle.
