Q&A for How to Diagnose a Non Working Air Conditioning in a Car

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Can a bad temp sensor cause AC not to work?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

Definitely! If the temperature sensor does not send a signal, then the AC will not turn on. Just keep in mind that these sensors are located deep in your HVAC system behind the dashboard, and can be difficult to inspect and replace.

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Question

How do you test a blend door?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

Start your vehicle and turn on the AC with the fan on high. Then, cycle through the selector options on your HVAC control, feeling for cold air from each position. Positions that don't blow cold air may have a temperature sensor issue, while positions that don't blow any air might have a blend door actuator problem.

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Question

How do I know if my AC fan is bad?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

Your AC fan will either have inconsistent air movement or no air movement at all.

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How do I know if my pulley is bad?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

The pulley either doesn't turn or turns inconsistently when the AC clutch engages.

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Question

What happens when an AC belt goes bad?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

You might notice a high-pitched squeal or chirp from the belt when the AC is turned on. There might also be intermittent cooling in the system as the belt gains and loses traction.

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How do I know if my AC clutch is bad?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

The tell-tale signs of a bad AC clutch are the clutch not engaging when the AC is turned on (and voltage is present); the clutch clicking or banging but not engaging when the AC is turned on; the clutch slipping in and out of gear when the AC is turned on; and/or the vehicle idle dropping noticeably when the AC is turned on.

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How do you know if your car AC is low on gas?

Ed Beery
Automotive Specialist
Ed Beery is an Automotive Specialist and the Owner of InTechgrity Automotive Excellence based in Denver, Colorado. With more than eight years of experience, he specializes in providing maintenance and repair services for both individuals and companies. Ed and the InTechgrity Automotive Excellence Team are approved by the American Automobile Association (AAA) for repairs and are Automotive Service Excellence (ASE) certified.

Ed Beery

Automotive Specialist

Expert Answer

Low or no gas might be the problem if air is flowing throughout the system when the AC is turned on; the air is not cold or cool and doesn't get cold or cool anywhere in the system; the AC compressor is turning; the AC clutch is not making noise; and the AC clutch engages when the AC is turned on.

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Question

Can a blown fuse box cause your AC not to work?

Community Answer

Sure, if the fuse that feeds your AC compressor or relays is blown and not delivering +12VDC you will have no AC.

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Question

What do I do if my A/C isn't blowing air?

Community Answer

Possibly either a fuse or the blower motor isn't working. Check the fuses under the hood, and check under your glove compartment for a cylinder shaped motor. With the A/C on, gently wiggle the cord to test for a short in the adapter. If this doesn't work, then you can use a fuse tester to see if your blower motor is getting power.

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My truck heat works; it defrosts, but only on 3 and 4. It only blows hot air on 3 and 4. I've put coolant in it, and it works for a few seconds, then stops. I checked for leaks, and it doesn't have any. What can I try next?

Community Answer

A blower motor may have a resistor problem if your air only blows on the high setting but will not blow on a lower setting.

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Question

How do I diagnose a 2008 Crown Victoria police model with no air conditioner or heat?

Community Answer

There could be a problem with your blower motor. Check the associated fuse/relay, and then diagnose the motor itself via physical inspection.

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Question

What do I do if I had the vacuum pulled and my a/c unit charged on my truck, but it is still blowing hot air?

Community Answer

There are other components that could also be bad. A recharge will only fix your system if the charge was low. If you have no leak and a fully charged system but only hot air then it could be the compressor, a relay, orifice tube clogged or another component. See a technician for advice.

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Question

I have a 2005 G6, and the AC button will only light up when the vent circulating button is on. This button also won't turn off unless the fan is not on at all, and there is not cold air blowing for the AC. What could be wrong?

Community Answer

Check to see if your AC clutch is engaging. If not, you could have a bad compressor or fuse; check the fuse first.

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Question

What if smoke comes from the vent when I turn the a/c or heat on in my car?

Community Answer

It's probably water vapor, not smoke. This is entirely normal, especially in humid environments. Unless it smells or doesn't dissipate, don't worry about it.

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Question

The air conditioner in my car will only blow air on the highest setting, and the temperature changes between cool and warm. What could be wrong with it, and how much would it cost to repair?

Community Answer

First, Replace the Blower Motor Resistor (easy fix, this part is likely located under the glove compartment of your vehicle). Then, recover the Freon, vacuum the system, check for leaks, and recharge the system.

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Question

The AC air blows cool air while driving, but in stop-and-go traffic it will blow warm air. What could it be?

gourav prasad

Community Answer

The car AC pumps cool air at an RPM of 1500+, so in order to get the cooling, you need to maintain an RPM of 1500+.

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Question

I have a 2002 Camry 2.4L 4 cyl. If my AC compressor breaks, can I still drive the car?

Community Answer

Yes, but you well need to see a mechanic to fix a smaller belt for you. Before driving it, with the compressor broken, you will not have access to use your AC.

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Question

I can hear the A/C turn on. The fan is running, but there's no air blowing. What could be the problem?

Community Answer

It's likely that the air ducts are plugged or the filter is plugged. It's best to take it to a mechanic.

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Question

My air conditioner works, but when it is on it makes a growling sound and air that comes through the vent burns my eyes and has a choking effect. What should I do?

Community Answer

First, get out of the car. It sounds like there is some kind of toxic chemical in the air. And second, take the vehicle to a mechanic ASAP.

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Question

I am only getting cold air out of the vents on one side of my car. What could be the problem?

Community Answer

If this problem is persistent on all vent settings, there's likely a blockage in the vent duct somewhere after the cabin filter, which would need to be diagnosed and cleared by a technician/mechanic, unless you have take-it-apart savvy yourself.

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Question

After charging the refrigerant, the A/C will work for a few days, then the air flow turns warm - hot. What can I do?

Community Answer

Sound like a freon leak. Best to get it fixed soon. Running the system with low freon levels can burn up the compressor.

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Will high pressure on my car's air conditioning cause it to not work?

Community Answer

Many vehicles have a safety that shuts off the compressor if too much refrigerant is pumped in.

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Question

What should I do if I added freon and the clutch is engaging, but it is blowing warm air?

Community Answer

If your compressor clutch is engaging you most likely have a leak big enough to let all the Freon out as soon as you fill it in. Check or have someone check the system for leaks.

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