Auto AC Repair DIY

What's happening with my auto A/C?

How do you test for an A/C system leak?

While we’re no C.S.I. unit, the ways to detect an A/C system leak are not far off from an episode of the ever popular investigation show.

Detecting leaks:

  • Black light enabled dyes. You read that right. A lot of refrigerants are pre-mixed with a special U.V.dye that shows up under black light. We’ll run a black light over your A/C system to see if any dye shows up.
  • Bring in the “sniffer.” A sniffer is a special device that hones in on the refrigerant’s chemical components. If there’s a leak, our sniffer will sniff it out.

My A/C isn’t as cold as it used to be, what’s going on?

There are several reasons an A/C system can lose its cool. Bring your ride to us as soon as you start noticing this symptom, it could mean the difference between needing a small repair, or worse, a large one.

Here’s what can cause your cold air to lose its cool.
The lack of precious cold air could be caused by:
  • A Freon leak caused by a failed o-ring, seal, hose or component
  • A clogged expansion tube or refrigerant charging hose
  • Failed compressor or compressor clutch
  • Failed blower motor or blower motor resistor
  • Damaged or failed condenser or evaporator
  • Vacuum leaks
  • Failed switch, fuse, relay, control module, blend door or solenoid

Leaks can be devastating. When an A/C system develops a leak, you have what’s called an “open system.” If you or your technician discovers the leak early, your repair will be less expensive. Unfortunately, if a leak has been affecting your cold air for a while, moisture will most likely have entered your A/C system and may have damaged other vital and expensive parts. Stay cool

Are there any system warning lights to alert me to an A/C problem?

Typically, no, but some vehicles have Driver Information Centers (DIC) that may display the status of many vehicle systems. Refer to your Owner’s Manual for more information

Why does my A/C have weak airflow?

We feel your pain and discomfort caused by weak airflow. The sweat alone is enough to drive any of us crazy. However, there are a lot of factors at play. If you notice reduced airflow early on –rather than later– take the right step and have it looked at before other fatal A/C system damage can occur.

Main causes of weak airflow:
  • Mold or mildew may have accumulated in the evaporator core from residual moisture that occurs during the cooling process. When this happens, air will have trouble reaching your air vents.
  • A hose has come loose. This usually happens with the blower hose that supplies air to the blower unit.
  • Ventilation fan is fried. If the fan’s not blowing, air won’t be flowing very well.
  • Seals. No, not those seals down by the pier. Core case seals, blower house seals or evaporator core case seals; All can open up and diminish air flow. A/C ventilation systems are very sensitive and must remain sealed. Once they’re opened, the whole system is compromised.
Recharging & refrigerant (freon) for the auto A/C

How do I find the charge ports on my A/C system?

Your auto A/C system includes 2 charge ports. One for the low side and one for the high side. The simple way to find them is to trace the lines. Usually, from the evaporator outlet, (near the firewall) follow the line to the A/C compressor. The LOW side port should be on this line. For systems using an accumulator, it may be one of the ports right on the accumulator. To locate the HIGH side port, locate the A/C compressor. Follow the line that goes to the condenser (usually the smaller of the two). The HIGH side port may be on the line between the compressor and the condenser OR it could be on the line after the condenser; between the condenser and the evaporator inlet. On R-134a systems, the HIGH side charge port will be larger than the LOW side port, and will require quick connect couplers to connect. If you are using an older set of R-12 gauges, don't worry! You can convert those gauges to work with R-134a!

Vacuum and the auto A/C System

Does the A/C system have to be vacuumed before recharging?

A: Yes, the A/C system should always be vacuumed before recharging. Vacuum removes air and moisture from the system. Removing moisture is important as it creates harmful acids when mixed with the refrigerants. Those acids will corrode the system internally and can cause restrictions at the orifice tube. On the other hand, air causes problems with high pressures and is very difficult to diagnose when it's in an A/C system. The air is considered a contaminant and is a 'non condensable'  Therefore, it will be trapped at the top of the condenser.  The only sure way to remove the air is to vacuum the system before recharging, and always be sure the hoses on your gauge set are purged of air.

How does air get into the system when I am recharging or adding refrigerant?

A: Typically when recharging the A/C system, the system is vacuumed, and you will not get air into the A/C system. However, when adding refrigerant or 'topping off' the A/C system, you can easily get air into the system right from the hoses on your gauge set. Before connecting to the system, if your gauge set hoses do not have refrigerant in them (being held by the quick couplers) then they are full of air. Connecting them to your A/C system and then adding refrigerant or freon will cause the air to be pushed into the system. Longer charge hoses create a bigger problem. To eliminate this, simply 'purge' the hoses. That's done by 'cracking' the hose at the threaded connection. Usually opening that connection about 1/4 to 1/2 turn will cause refrigerant to leak. Once you're leaking refrigerant, you know you have the air removed or purged from the charge hose. You're ready to add refrigerant.

What's the best type of vacuum pump to use for auto A/C service?

A: Typically there isn't a 'better' type of pump to use. It just has to be able to pull deep vacuum in order to boil moisture and remove the air that may be in the system. When you're deciding on a vacuum pump, you should pay more attention to the 'micron' rating. That's the level of vacuum that the pump is rated for. The lower the number, the better the pump. Water only starts to boil at levels of vacuum under 1,500 micron. Deep vacuum is typically at levels under 750. You should really aim for 500 microns or under. The most popular type of vacuum pump is the rotary vane design.  Our Kozyvacu Models are all capable to vacuum your car vacuum system.

How do I vacuum the Auto A/C System?

A: In order to vacuum the auto A/C system, you need a standard manifold gauge set and vacuum pump. Start by being sure that all control valves on the gauge set are closed. With the pressure gauges connected to the A/C system (red hose to high pressure side and blue hose to the low pressure side) connect the yellow (center hose) to the vacuum pump. Start the vacuum pump and then open both high and low side control valves on the manifold gauge set. This assures that vacuum is being pulled throughout the A/C system. Typically vacuum is pulled for about 1/2 hour, but that will depend on the condition of the system and the work being performed. In the case of regular maintenance, a 1/2 hour vacuum at 29.9" should be fine. Where a system has been contaminated or suffered catastrophic failure (ie.: seized compressor) it's generally a good idea to vacuum for at least 1 hour or more to assure a totally dry system. It's also important to assure that your vacuum pump pulls deep vacuum. Water does not boil until the level of vacuum is under 1,500 microns. Deep vacuum is considered to be under 750 microns. Ideally, for automotive service, you should attain at least 200-300 micron vacuum if not lower. See more details about "vacuum basics". The following  two Youtube video is very help for you to vacuum your AUTO A/C System

1.How to Pull a Vacuum on an AC System - Step by Step

2. Vehicle A/C System Evacuation and Recharge - DIY

How does air get into the system when I am recharging or adding refrigerant?

Typically when recharging the A/C system, the system is vacuumed, and you will not get air into the A/C system. However, when adding refrigerant or 'topping off' the A/C system, you can easily get air into the system right from the hoses on your gauge set. Before connecting to the system, if your gauge set hoses do not have refrigerant in them (being held by the quick couplers) then they are full of air. Connecting them to your A/C system and then adding refrigerant or freon will cause the air to be pushed into the system. Longer charge hoses create a bigger problem. To eliminate this, simply 'purge' the hoses. That's done by 'cracking' the hose at the threaded connection. Usually opening that connection about 1/4 to 1/2 turn will cause refrigerant to leak. Once you're leaking refrigerant, you know you have the air removed or purged from the charge hose. You're ready to add refrigerant.

What's the best type of vacuum pump to use for auto A/C service?

Typically there isn't a 'better' type of pump to use. It just has to be able to pull deep vacuum in order to boil moisture and remove the air that may be in the system. When you're deciding on a vacuum pump, you should pay more attention to the 'micron' rating. That's the level of vacuum that the pump is rated for. The lower the number, the better the pump. Water only starts to boil at levels of vacuum under 1,500 micron. Deep vacuum is typically at levels under 750. You should really aim for 500 microns or under. The most popular type of vacuum pump is the rotary vane design. Our Kozyvacu Models are all capable to vacuum your car vacuum system.

How do I vacuum the Auto A/C System?

In order to vacuum the auto A/C system, you need a standard manifold gauge set and vacuum pump. Start by being sure that all control valves on the gauge set are closed. With the pressure gauges connected to the A/C system (red hose to high pressure side and blue hose to the low pressure side) connect the yellow (center hose) to the vacuum pump. Start the vacuum pump and then open both high and low side control valves on the manifold gauge set. This assures that vacuum is being pulled throughout the A/C system. Typically vacuum is pulled for about 1/2 hour, but that will depend on the condition of the system and the work being performed. In the case of regular maintenance, a 1/2 hour vacuum at 29.9" should be fine. Where a system has been contaminated or suffered catastrophic failure (ie.: seized compressor) it's generally a good idea to vacuum for at least 1 hour or more to assure a totally dry system. It's also important to assure that your vacuum pump pulls deep vacuum. Water does not boil until the level of vacuum is under 1,500 microns. Deep vacuum is considered to be under 750 microns. Ideally, for automotive service, you should attain at least 200-300 micron vacuum if not lower. See more details about "vacuum basics". The following two Youtube video is very help for you to vacuum your AUTO A/C System

1.How to Pull a Vacuum on an AC System - Step by Step

2.Vehicle A/C System Evacuation and Recharge – DIY

Orifice Tubes

What about TXV's and expansion valves? Can they be checked?

A: The answer really depends on which type of expansion valve your auto A/C system has. The typical type expansion valve that has an external capillary tube (where the sensing bulb is usually attached to the evaporator outlet) can be tested. The test process is to remove the sensing bulb (gently). Use caution so that you do not 'kink' or bend the tube. With the A/C system charged and running, FREEZING the sensing bulb should cause the low side pressure to rise over 45 p.s.i. WARMING the sensing bulb should cause the low side pressure to drop to zero and possibly vacuum. For a valve to be considered 'good', BOTH pressure gauge reading conditions must be met.

I can't find the orifice tube on my A/C System. How do I locate it?

The orifice tube will always be in the liquid line between the condenser and the evaporator inlet. Typically, they are installed right in the inlet of the evaporator. However, on more current model vehicles they may be in the A/C condenser outlet or actually 'in-line' between the condenser and the evaporator. This illustration will help detail the location of the orifice tube on your A/C system. Also watch for the 'dimples' in the line. Those dimples secure the orifice tube in place. Therefore, wherever you find the dimples, you will find the orifice tube.

Why is the location of the orifice tube changed on some vehicles?

The orifice tube is a fixed opening. When the A/C system shuts off, both sides of the system will equalize through the orifice tube. When that happens, there is a definite 'hissing' sound. Because that sound can be heard inside the passenger compartment of the vehicle, it was decided to move the orifice tube further up the liquid line (on some vehicles) to reduce the noise.be.

Does the orifice tube have to be installed in a specific direction?

Yes! The orifice tube does have to be installed in a specific direction. Simply speaking, there is a 'long' and 'short' screen on each orifice tube. The 'long' screen is the INLET filter. Therefore, it should be at the inlet side (from the condenser). The 'short' filter screen should be pointing towards the evaporator (or outlet of the orifice tube). Also, if you look closely, there is usually a flow arrow that will show you the proper direction of flow through the orifice tube. It's in the plastic portion of the orifice tube. That will tell you what direction the refrigerant is expected to flow through the orifice tube.

Refrigerant oil in the auto A/C system

Do I have to add refrigerant oil the the A/C system when I recharge?

The general rule is that the automotive A/C system is a closed system, and unless oil has leaked out, there should be no reason to 'just add oil' every time you recharge the system. Having said that, it's also true that components like compressor shaft seals and some 'quick connect' fittings will leak oil and may not even show a sign. Adding an ounce of refrigerant oil to an otherwise leak free system is not going to hurt it. Just don't add too much because an oil overcharge can cause poor cooling problems.

How much refrigerant oil should I add to the A/C system when recharging?

As outlined above, there may not be a requirement to add oil to the A/C system every time it's recharged. However, if the system requires oil, you should only be adding the amount of oil that's been lost. With leaks or 'normal' loss of refrigerant oil through the a/c compressor shaft seals it may be difficult to determine exactly how much to add. Therefore, you should follow the general 'rules'. Adding 1-2 ounces for loss through small leaks or through the compressor shaft seal is acceptable. When replacing components, there are additional guidelines that should be followed. They are; A/C Condenser - 1 oz.; Accumulator or receiver drier - 1 oz.; Evaporator - 3 oz.; Compressor - Generally, the amount removed plus one ounce (1oz.). For more detailed refrigerant oil specifications, follow the service manual for your specific application.

When adding refrigerant oil to the A/C system, where do I add it?

There is no hard and fast rule about where to add refrigerant oil to the automotive A/C system. If you are replacing a component (like an accumulator or receiver drier) the refrigerant oil can be added right to the part. Simply measure the required amount and pour it into the part before installing it. If you are adding to a closed system (where no parts are being replaced), you will need to add the refrigerant oil using an oil injector or you will have to open the system to pour it in. Typically, the best place to add the oil would be to the low side of the system. Refrigerant oil will circulate throughout the system and 'seek' it's own level once the system is operating.

Auto A/C Component replacement

What if I am replacing the A/C compressor? Where do I add that oil?

When replacing the A/C compressor, you should make all attempts to follow the specific instructions provided with that compressor. Some compressors will ship with the oil already installed; others will ship virtually dry. If no manufacturer's instructions are available, you should start by draining all the oil from the new replacement (or remanufactured replacement) and from your old compressor. Measure the amount drained from your old compressor and add that amount plus one ounce to the replacement. That oil should be added directly into the suction port of the A/C compressor. If you can not drain any oil from your old compressor, you should add about 1/3 of the total system charge of oil to the compressor. As a rule, the A/C system will hold between 8-12 ounces of oil. Therefore, depending on your particular system, you would add between 2-1/2 and 4 ounces into the replacement compressor. For best results, use Polymax2 refrigerant oil because it's non-hygroscopic (will not attract moisture) and is approved for use with all oils. Also consider adding an in-line A/C filter for added protection for your new compressor. These in-line filters are almost like insurance for your A/C Compressor.

Check out the details how to change AC compressor in the following Youtube video:

Why can't I replace an A/C hose with fittings and a hose clamp?

On older R-12 A/C Systems, hoses used what was known as a "Three Ring Barb" style fitting. With those fittings, you could install a new piece of hose and utilize a standard 'worm gear' hose clamp to secure the hose. On current auto A/C systems using R-134a refrigerant, all hoses are barrier type A/C hose. Three ring barb fittings should not be used on barrier hose because the barbs pierce the inner nylon core of the hose, causing it to leak prematurely. All R-134a systems should use barrier hose and proper 'bead lock' fittings. Those fitting incorporate the crimp ferrule (or shell) into part of the fitting, and they will have to be crimper using a A/C hose crimper.

Do I have to replace the complete A/C hose assembly or can it be repaired?

No, you don't have to replace the complete assembly. It's typical that many hose sections leak at the hose crimp. That small hose section could be part of a long A/C hose assembly that's costly to purchase, and does not need replacement. You can repair just the section of hose by cutting the ferrule and using a simple unique hose repair system that lets you replace the ferrule and hose section only. That way, you don't have to replace the complete A/C hose assembly. You just replace the section of A/C hose that's leaking. To complete the job, you will have to be able to measure the A/C hose and fittings on your vehicle, and then complete the A/C hose repair in three simple steps.

Measuring the tube or fitting size:

As illustrated above, simply measure the tube section of fitting size by taking a measurement of the tube O.D. (outside diameter) as close to the section of A/C hose as possible. Then refer to the chart below to understand what size of A/C hose or fitting is required to complete the repair.

TUBE or HOSE O.D. = Outside Diameter
TUBE or HOSE I.D. = Inside Diameter

Tube O.D. Normal Size A/C Hose I.D. A/C Hose O.D
3/8" #6 5/16" 3/4"
1/2" #8 13/32" 29/32"
5/8" #10 1/2" 1"
3/4" #12 5/8" 1-3/32"

Note about the A/C hose sizes listed in the chart: The above chart provides A/C hose I.D. and O.D. of standard barrier refrigerant hoses. In some applications, the original manufacturer may use 'Reduced Diameter' barrier hose. Reduced Diameter hose is the same INSIDE DIAMETER as standard barrier hose, but the OUTSIDE DIAMETER is reduced. It allows for tighter bends under the hood. However reduced diameter A/C hose can be replaced with standard barrier hose without any effect on fit or performance of the A/C system.

3 Steps A/C Hose Repair:

Here's a series of photos of an actual A/C hose repair completed with the Crimpmate 3 Step hose repair system. You will be able to see just how easy it is to repair any A/C hose and get professional O.E. style results all the time!

Cut the original hose crimp to remove it from the hose. It helps to secure the tube section in a bench vice. In this photo, you can see that we made two cuts, being careful not to cut through the hose or damage the beads that hold the original hose ferrule.
The original A/C hose is removed and the original ferrule can be pulled from the beads that held it in place on the fitting. Be sure not to damage the original tube section when cutting. That could upset the sealing surfaces and create a leak at your new hose crimp.
You can see that we have installed the new ferrule first, and then positioned the proper retainer clip into the groove (between the two bead) that originally held the ferrule. We're ready to install the hose
With the hose installed and pushed right up to the beads (where the retainer clip was installed) we simply slide the new ferrule on top of the hose. We're ready to complete the job by simply crimping the new ferrule and hose connection. That will give us a leak free repair with the same look and feel as the O.E. hose. All without having th replace the entire hose assembly.

How do I measure the fitting or hose on my A/C system?

Always determine the fitting size by taking a measurement of a straight section of the tube, as close to the hose section as possible. You will find that typically, auto A/C tube sections are 3/8", 1/2", 5/8" or 3/4" in O.D. (Outside Diameter). Use that measurement to determine which size fitting and hose is required for your repair.

Can I repair the rear A/C hoses or lines on a vehicle with rear A/C?

Yes, you can usually repair the rear A/C lines that run under the vehicle for the rear evaporator. Typically, these hoses or lines are metal because they are exposed to all the harsh road and weather conditions as they run the entire length of the vehicle on underneath. In most cases, the entire line does not have to be replaced. (Complete line replacements are only available from the dealer). The rear A/C lines usually rust or corrode where there are clamps holding them or in areas where they have been exdposed. To repair the lines, you first must be able to determine the actual size of the tube. With that, you can use the rear A/C line repair kits to fix just the section that's leaking. Just cut away the corroded section and install the repair kit.

Does the A/C system have to be vacuumed before recharging?

Yes, the A/C system should always be vacuumed before recharging. Vacuum removes air and moisture from the system. Removing moisture is important as it creates harmful acids when mixed with the refrigerants. Those acids will corrode the system internally and can cause restrictions at the orifice tube. On the other hand, air causes problems with high pressures and is very difficult to diagnose when it's in an A/C system. The air is considered a contaminant and is a 'non condensable' Therefore, it will be trapped at the top of the condenser. The only sure way to remove the air is to vacuum the system before recharging, and always be sure the hoses on your gauge set are purged of air.

The Auto A/C Compressor Clutch

My A/C Compressor clutch slips when the compressor engages? What's the problem?

Every A/C compressor clutch has a specific 'air gap'. That is the distance between the clutch plate (or clutch hub) and the pulley. If the clutch is slipping when the compressor trys to engage, it is most likely that the air gap is too large. Typically the air gap will change over time. In most cases, the gap increases. When it increases too much, the clutch plate will start to slip when the compressor engages. It should also be noted that there are other problems that could cause compressor clutch slipping; typically insufficient voltage or excess high pressures. Those possible causes require other equipment or pressure gauges to check.

The A/C Clutch will not engage. What could the problem be?

There are several different reasons why the A/C compressor clutch does not engage when you turn the A/C system on. Typically, the most common problems are:

  • Low refrigerant prevents the cycling switch from engaging the compressor. That's because it's acting as a safety for the compressor. This can be tested by jumping the switch. Also check system pressures. Low refrigerant pressures would indicate the charge is low and the system will have to be leak tested and recharged to fix the problem.
  • Clutch coils can also fail. The coil is what creates the magnetic field to 'pull' the clutch hub into the pulley, engaging the clutch. The coil can be tested using an Ohm meter to assure continuity.
  • Air Gap; That's the distance between the front hub and the pulley. Typically, it should be about .025" or about the thickness of a business card. When the air gap is too wide, the magnetic field is not strong enough to pull the hub in. The clutch air gap can be adjusted (usually on the vehicle). Also see 'clutch slipping' below.
  • Not enough voltage; the clutch requires a full 12 volts in order to create the required magnetic field. When contacts and connections are corroded, there may be a drop in voltage. Check voltage at the clutch to assure proper voltage is present.

Note that these are the most common reasons why the A/C compressor clutch does not engage. Other electrical problems (ie.: control head, relays, etc.) will require a wiring diagram for diagnosis

Offensive Odors from your A/C system?

What can I do to eliminate the foul odor from my auto A/C system?

The foul odor is a result of the basic design of the auto A/C system. The system is technically known as a ‘series re-heat system’. That’s because all the air entering into the vehicle passes over the evaporator regardless of whether you’re calling for cooling, heat or some blend of hot and cold air. Therefore, the air side (or inlet side) of the evaporator faces all the pollutants and contaminants in the air. Because the evaporator is usually wet or moist with condensation, that dirt and debris tends to stick to the evaporator face. Those are perfect conditions for the start of bacteria, mold and mildew. To eliminate the problem, you have to apply something to treat the odor and help eliminate the odor causing bacteria and mold. The following video tells you how to fix it.

Retrofit Air-Conditioning
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