How do I diagnose my AC leak?

[MTL_4runner]

I thought it would be nice to start a thread on how to fix AC systems within the limit of what the homeowner can do and check. I've had some issue with my Honda Civic AC going out, but really AC systems are so similar it doesn't matter which make of vehicle your trouble shooting.

I thought I'd put a bunch of good info togther in one thread so people have a place to go to when their A/C decides to not play fair mid summer.

[MTL_4runner]

Great article I came across...

A/C COOLING PROBLEM?

The most likely cause of an automotive air conditioner cooling problem is no refrigerant in the system. If the refrigerant has escaped past a leaky compressor or O-ring seal, leaked out of a pinhole in the evaporator or condenser, or seeped out through a leaky hose, the leak needs to be identified and repaired before the system is recharged.

On many systems, the compressor will not turn on if the refrigerant is low because the "low pressure safety switch" prevents the compressor clutch from engaging if system pressure is low. This protects the compressor from possible damage caused by a lack of lubrication.

One of the first things you should check, therefore, is compressor engagement. If the compressors magnetic clutch is not engaging when the A/C is turned on, the problem may be a blown fuse or a wiring problem. If the fuse is blown, replacing it may restore cooling temporarily. But the underlying reason for the fuse blowing in the first place needs to be identified and corrected to prevent the same thing from happening again.

If the magnetic clutch is receiving voltage but is not engaging the compressor, the clutch is defective and needs to be replaced. If there is any evidence of leakage around the compressor shaft seal, the seal should also be replaced.

If the clutch works but fails to turn the compressor (the belt may squeal in protest!), the compressor has seized and needs to be replaced.

Compressor failures are usually the result of loss of lubrication, which in turn may be due to low refrigerant in the system, a blockage (such as a plugged orifice tube which prevents refrigerant and oil from circulating to the compressor), loss of lubricant due to leaks or improper service procedures (not adding oil to the system to compensate for oil lost through leakage or component replacement), or use of the wrong type of lubricant.

R-12 systems require mineral oil while R-134a systems require various types of PAG oil or POE oil. Using mineral oil in a newer R-134a system can cause serious lubrication problems as can using the wrong grade (viscosity) of PAG oil. Always follow the vehicle or lubricant manufacturers compressor oil recommendations.

The next thing you should check when troubleshooting a no cooling problem is system pressure. For this, you need a set of A/C service gauges. Attach your service gauges to the high and low service fittings. If both the high and low side pressure gauges read low, the system is low and needs recharging. But before any refrigerant is added, check for leaks to find out where the refrigerant is going.

AIR CONDITIONING PROBLEM: REFRIGERANT LEAKS

All vehicles leak some refrigerant past seals and through microscopic pores in hoses. The older the vehicle, the higher the rate of seepage. Newer vehicles have better seals and barrier style hoses so typically leak less than a few tenths of an ounce of refrigerant a year. But system capacities also tend to be smaller on newer vehicles, so any loss of refrigerant will have more of an adverse effect on cooling performance.

Various methods can be used to check for leaks. The telltale oil stains and wet spots that indicate leaks on older R-12 systems are less apparent on the newer R-134a systems because PAG lubricants are not as "oily" as mineral oil. This makes it harder to see leaks.

Leaks can be found by adding special dye to the system (available in pressurized cans premixed with refrigerant), an electronic leak detector, or plain old soapy water (spray on hose connections and watch for bubbles -- requires adding some refrierant to system first and turning the A/C on). Once you've found a leak, repairs should be made prior to fully recharging the system. Most leak repairs involve replacing O-rings, seals or hoses. But if the evaporator or condenser are leaking, repairs can be expensive.

AIR CONDITIONER PROBLEM: INTERMITTENT COOLING

An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.

For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that�s contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.

Some refrigerant identifier equipment can detect air in the system as well as other contaminants. You should always use an identifier to check the refrigerant before servicing the system to prevent cross-contamination of your recovery and recycling equipment.

AIR CONDITIONING PROBLEM: NOISE

Noise from the compressor usually means the compressor is on its way out. But noise can also be caused by cross-contaminated refrigerant (operating pressure too high), air in the system or the wrong type of compressor lubricant.

Noise can also be caused by hoses or other parts rattling against other components in the engine compartment. Check the routing of the hoses, support brackets, etc., to pinpoint the noise.

TROUBLESHOOTING AIR CONDITIONING ODOR

If a vehicles air conditioner blows out air that smells like the inside of old gym sneaker when the A/C is turned on, microbes are growing on the evaporator. Mold likes damp, dark places. Bacteria can also thrive under such conditions. Besides smelling bad, it can be unhealthy to breathe (ever hear of Legionnaires Disease?).

To get rid of the unwanted organisms, various chemicals can be sprayed on the evaporator directly or through the blower ducts or air intake. Many replacement evaporators have a special chemical coating that inhibits the growth of mold and bacteria. The drainage tubes that carry condensation away from the evaporator should also be inspected and cleaned.

A/C FLUSHING

If the compressor has failed, or the system is full of sludge or contamination, the condenser, evaporator and hoses should all be flushed with an approved flushing chemical (such as Dura 141b) to clean the A/C system. Flushing can help prevent repeat compressor failures and system blockages by dislodging and cleaning out sludge and debris. Replacing badly contaminated parts such as the condenser, accumulator or receiver-drier and orifice tube or expansion valve is another way to get rid of these contaminants, but flushing is usually a more practical and economical choice. Regardless of which approach you use, the orifice tube or expansion valve should always be replaced when contamination is found.

NOTE: Some types of compressors can be very difficult to flush completely. These include "parallel" flow condensers and those with extremely small passegeways. If contaminated, these types of condensers must be replaced to reduce the risk of a repeat compressor failure. Installing ain in-line filter is also recommended for added insurance,

When a compressor fails, a lot of metallic debris is often thrown into the system. Most of this debris collects in the condenser where it can cause blockages that reduce cooling performance. If the debris is carried through the condenser and enters the liquid line, it can plug the orifice tube or expansion valve. This can block the flow of refrigerant and lubricating oil causing a loss of cooling and possible compressor damage. Debris can also migrate backwards from the compressor through the suction hose causing blockages in the accumulator or receiver-drier.

Another source of trouble can be debris from old hoses that are deteriorating internally. Tiny flakes of rubber can be carried along to the orifice tube or expansion valve and cause a blockage.

Sludge is usually the result of moisture-contamination. The blackish goo that results can damage the compressor and plug the orifice tube or expansion valve. The moisture-absorbing "desiccant" in the accumulator or receiver-drier is supposed to prevent this from happening. But the desiccant can only hold so much moisture. Once saturated, sludge begins to form. So you should also replace the accumulator or receiver-drier if the system is contaminated, has leaks or must be opened up for repairs.

Another reason for flushing is to remove residual lubricating oil from the system. This should be done when retrofitting an R-12 system to R-134a. It should also be done if the lubricating oil is contaminated or the system contains the wrong type of oil for the application. Flushing out the old oil can prevent oil overcharging, reduced cooling performance and/or lubrication incompatibility problems.

For added insurance after flushing, you can install a high side filter to protect the orifice tube or expansion valve from any residual debris that might still be in the system, and/or a second filter in the suction hose to protect the compressor.

R134A RETROFIT

As long as R-12 is available, there is no real reason to convert older vehicles to R-134a. That is because R-12 systems cool best when charged with R-12 refrigerant. But converting to R-134a does make sense if your A/C system requires major A/C repairs (such as a new compressor, condenser or evaporator). The extra cost involved to make the changeover to R-134a does not add that much to the total repair bill.

A basic retrofit procedure can be done one of two ways. The "Type 1" retrofit follows the OEM recommended procedure and generally involves removing all the old mineral oil from the system, replacing the accumulator or receiver-drier with one that contains a desiccant (X-7) which is compatible with R-134a, replacing O-rings (if required), installing or replacing a high pressure cutout switch and/or orifice tube (if required), then adding the specified PAG oil and recharging the system with R-134a. Federal law also requires the installation of R-134a fittings on the high and low service ports to reduce the chance of refrigerant cross-contamination the next time the vehicle is serviced, and labels that identify the system has been converted to R-134a. For more information, see the R134A RETROFIT GUIDE program featured on this website.

A "Type 2" procedure is more of a "quick and cheap" approach to retrofit. On many 1989 through 1993 vintage vehicles, the R-12 A/C systems can be converted to R-134a by simply recovering any of the R-12 that is left in the system (NOTE: it is illegal to vent refrigerant into the atmosphere!), adding POE oil (which is compatible with both types of refrigerant), and then recharging with R-134a.

NOTE: Type 2 conversions cannot always be done on some vehicles because their compressors may not be compatible with R-134a (any compressor with Viton seals has to be replaced). This includes original equipment compressors such as Tecumseh HR980, some Keihin compressors and some Panasonic rotary valve style compressors in older Nissan vehicles.

Durability is another concern. Because R-134a raises compressor discharge pressures and increases the compressors work load, some lightweight compressors may not be rugged enough to tolerate R-134a over the long haul. This applies to the Harrison DA6 and Ford FX-15 compressors. The Harrison DA6 can be replaced with a HD-6, HR-6 or HR-6HE compressor. The Ford FX-15 compressor can be replaced with a FS-10 compressor.

http://www.aa1car.com/library/ac98.htm

[MTL_4runner]

So what should the high and low side pressures be on a well functioning Toyota A/C system running R134a?

Well the answer to that question is that it depends on what the temperature isoutside at the time the A/C is being tested. The warmer it is outside, the higher the pressures will be in the system.

Here's a conversion chart which shows you high/low side vs outside temp:
http://www.autoacforum.com/aacf/ptchart.cfm

Toyota's FSM recommends:

Low pressure side:
0.15 – 0.25 MPa (1.5 – 2.5 kgf/cm2) = 22-36 PSI

High pressure side:
1.37 – 1.57 MPa (14 – 16 kgf/cm2) = 199-228 PSI

Toyota FSM says that the system is full when no more bubbles (or very few) can be seen in the sight glass.

[MTL_4runner]

Methods to find AC leaks:

Electronic Refrigerant Leak Detectors

Electronic Refrigerant Leak Detectors are the quickest and easiest to use of the three methods. Most of the time you will have no idea where the refrigerant is leaking and have to narrow down the possible areas. A electronic refrigerant leak detector can get you very close to the location of the leak and from there you can get more precise. Some of the better models will allow to crank up the sensitivity once you get the area found. For very small leaks you can wrap the suspected area in cling wrap or a rag to try and contain the refrigerant. When you unwrap the area, put in the refrigerant leak detector and see if you get a reading. Remember, refrigerant is heavier than air and it will sink to the ground. It is best to sniff under tubing and compartments when looking for it.



Ultrasonic Leak Detectors

These are state of the art leak detectors and are the newest tool to find refrigerant leaks. They operate on the principle of sound detection. Instead of sniffing for refrigerant gas they listen for the sound it makes as Freon escapes the system. To use an ultrasonic leak detector the system should be pressured in order for the refrigerant to leak out and make noise. Also, the work area must be totally silent. Remember it is looking for sound and no background noise is imperative. This is the main drawback to using an ultrasonic leak detector. Very few auto shops are quiet enough to use it effectively.




Ultraviolet Dye Leak Detectors

This third method ultraviolet dye is injected into the air conditioning system and in theory should escape with the refrigerant. Commonly, an auto shops have an ultraviolet leak detection kit that has all of the tools necessary to complete this task. Generally these kits come with ultraviolet lamp or ultraviolet flashlight, a dye injector, safety glasses and ultraviolet dye. This method is the most technically complex of the three and is the messiest. You have to inject the ultraviolet dye into the system and wait for it to leak out. The dye can be messy and get all over the place. It gets in you’re A/C system, your refrigerant manifold gauges and you. However once you shine your ultraviolet flashlight and spot the leak, you usually can see exactly where it is.



I usually prefer to use the dye method since I've tried the other two and found that leaks are very tough to find by the other methods and the likelyhood of a false leak using the "sniffers" is very high (almost to the point where they are useless). This does not mean that all leaks can be found using dye either, but I find it the most helpful. Use the dye in combination with a soapy water solution (similar to what you'd use to find tire leaks) will find 99% of the issues you'd likely come across.

[MTL_4runner]

Ok, I'm running into issues even finding DIY cans of R-134a up here in Canada.
Are the DIY cans illegal up here or something? Anyone know?

[MTL_4runner]

Ok, I'm running into issues even finding DIY cans of R-134a up here in Canada.
Are the DIY cans illegal up here or something? Anyone know?

OK it looks like wonderful O-Canada has decided only people with special licenses can get their hands on R-134a up here so getting DIY cans are impossible. It is truely a mechanic only type of job unless you live near the US border and can do all the work on that side (they will not let you back across with any R-134a in your posession as far as I am aware.....someone correct me if this is not true). It's very hard to work on this stuff anyway and getting all the proper tools is just not practical for the home mechanic. I will say a good set of manifold gauges (which show high and low pressure sides) can come in handy for diagnosis (or topping off the system if you live in the US).

I got a set of these off eBay for about $80 used:


Harbor Freight sells a decent set for just $35 new (quality is less but hey they'll work):
http://www.harborfreight.com/cpi/cta...emnumber=92649

[MTL_4runner]

My A/C doesn't work now how do I troubleshoot it?

There's still a few things you can do to test your A/C system and see if something is wrong. The first thing is note if the compressor is clicking on at all. You should be able to see it turning on the front of the engine with the A/C button pushed and the fan on high. If you don't, then there may be a few things causing this as explained below. Next check all your fuses and relays, change any blown fuses and swap relays to ensure that is not an issue if the A/C is not coming on at all.

Here's a list of things to check if cool air comes out only at high engine RPM:
1. Refrigerant volume
2. Refrigerant pressure
3. Drive belt
4. Magnetic clutch
5. Compressor
6. Pressure switch
7. Thermistor
8. A/C switch
9. A/C amplifier
10.Heater control assembly
11.Wire harness

Here's a list of things to check if you have insufficient cooling:
1. Refrigerant volume
2. Drive belt
3. Magnetic clutch
4. Compressor
5. Condenser
6. Receiver
7. Expansion valve
8. Evaporator
9. Refrigerant lines
10.Pressure switch
11.A/C amplifier
12.Heater control assembly

I'll go over some of the more common ones to check.

What if the compressor turns on but the cooling is poor?

If it is turning, but you're not getting cold air, then you should look at the sight glass and look for bubbles while the compressor is running (the vehcile should be in the shade to keep temps down). If you see streams of bubbles then take it to a shop for recharging or hook up the manifold gauges and charge it yourself. If the sight glass is clear while the compressor is running or has only occasional bubbles, but the manifold gauges are not normal pressures and you still have poor performance, then you need to start looking into other components being the issue such as the compressor being bad, blockage in the evaporator, etc. These parts can be replaced but at the very least you'll need to take it to a shop to have the entire system evacuated before you work on it.

What if the compressor isn't turning on?

If the compressor is not turning at all, then you'll need to hook up a set of gauges to verify that there is pressure in the system. If your A/C just stopped working and find no pressure in the system at all then you've got a pretty decent leak somewhere that needs attention. If the system has below 28 psi in it, then you may just be low on refrigerant (use your manifold gauge set to veify pressure in the system). The pressure sensor will turn off for both too high and too low pressure so if pressure is above 455 psi or below 28 psi then the sensor will not have continuity. The way to test this is to locate the A/C pressure sensor, pull the electrical connector and use a piece of wire to jump the contacts. If this causes the compressor to turn on, then the system is either low on charge or the pressure sensor itself is bad. Check the sensor itself with a DMM for continuity. If the sensor is not continuous, then the pressure in the system is too low or the sensor is bad. If the sensor is continuous, then you either have a broken wire, bad electrical connection or need to check the A/C clutch.

The pressure sensor isn't the issue and the clutch still didn't turn on, now what?

If you checked the A/C pressure sensor and everything is fine there, the last thing is to verify that the magnetic A/C clutch will come on when power is applied. The engine does not have to be on for this procedure. You need to locate the electrical connection coming off the clutch (just follow the wires off the clutch at the front of the compressor, the connector will be within 6-8 inches of it). Connect the positive (+) lead from the battery to terminal on the magnetic clutch connector and the negative (–) lead to the body ground. Check that the magnetic clutch is energized. If it does not, then the clutch needs to be replaced. If it does, check the harness and switches to be sure the clutch is being activated properly.

So how do you add refrigerant to the A/C system?

If your system had no refrigerant in the lines at all, you should bring it to a shop and have them pull a vacuum on the system to evacuate any moisture or air in the lines and then they should purge the system with 50 psi nitrogen. If the system holds a vacuum you may want to have them use a UV dye to check for leaks just in case since if it holds a vaccum it may be a very slow leak but over time it may still leak. Address any leaky parts right away and replace them before you try and recharge. If all's well, you can move on to the actual recharging step.

Start the recharging process by making sure your red/blue hand valves on your manifold gauge set are closed then hook up your red/blue hoses to the high and low service ports (red is high, blue is low) and screw down the valve depressors to allow pressure in the lines. The gauges should now read any pressure remaining in the lines. NEVER add refrigerant to the high side, only the low side of the system. Thank god this is hard to do since the fittings are different and the kits you buy only fit the low side valve.....the service caps are also marked with an H or an L to limit confusion. Attach a can of R-134a to the yellow hose (make sure to cap any other valves on the manifold that are open) and use the can tap to pierce the top of the can and back it off to allow the gas to flow. If the can gets very cold during this process, you can submerse it in a pan of warm water to help promote the flow of gas into the system. Now turn the engine on and put the A/C in the car on full blast and begin to slowly open the blue (low side valve) manifold hand valve. You only need to add enough to remove most of the bubbles from the sight glass while the compressor is running.....it may take 20-30 seconds to stabilize and clear the bubbles so do this process very slowly. Once the bubbles are gone and the system has stabilized at the proper pressures, close all the valves, remove the gauges and recap the service ports.

What refrigerant do I have?

If your vehicle was made before 1993, there's a great probability that it uses R-12, or Freon, as a refrigerant. After 1993, all vehicles in the United States were required by the EPA to use R-134a as a refrigerant. The future holds even more refrigerant alternatives but, for the time being, these two refrigerants are the heavy hitters of automotive air conditioning systems. You can also tell by the valves on the lines. The older R-12 vehicles have screw on type valves versus the R-134a type which are a quick disconnect similar to what is used on air compressor lines.

R-12 service ports vs R-134a service ports:


Again R-12 vs R-134a:


Good articles on switching from R-12 to R-134a if you are looking to do so:
http://www.corvettemagazine.com/2006...conversion.asp
http://www.thirdgen.org/retrofitac

[cHRiSCOe]

What would you recommend if I have a clicking sound coming from under my hood when the a/c is on?

[20005spd]

a clicking sound under the hood is most likely your a/c compressor clutch engaging and disengaging, which is normal. it will cycle on and off depending on what is needed to maintain the outlet temps. yours could be cycling to much due to a problem with the system, or the clutch could be damaged

[cHRiSCOe]

I'm no car expert but I know this is not normal. I have never heard it click before but my heater has started sucking lately and I'm expecting the a/c will suck too this summer. Is there any do it yourself checks I could do before I take it somewhere?