A/C Inspection Tips
The best way to begin any A/C repair is with a thorough A/C inspection of the components since the problem can stem from a number of things. After checking components like the belts, the hoses and the related connections, the next step is a visual inspection of the A/C compressor. This can be challenging on some vehicles because they can be well hidden.
So what do you want to look for? Well, you need to check for any oil leakage and inspect the clutch and the bearing for good condition.
Note: To perform detailed inspections, you might want to look into acquiring a flexible automotive inspection-type mirror to allow you to see into some of those tight spots and find out what’s going on in any particular area.
Next, check the compressor clutch itself. You’ll find that there’s an air gap between the compressor clutch and the bearing face. Inspect that clutch air gap for its recommended spacing. To measure the air gap, you need to slide a gap gauge between the compressor clutch and the bearing face. Verify that it’s not thinner than 0.014” and not greater than 0.030”.
Did You Know… Most compressor failures are caused by loss of lubricant and/or refrigerant. Repeat failures are usually due to system contamination (sludge or metallic particles from a previous compressor failure).
If you just need to do a quick gap test and you don’t have access to service information, try a money test. It’s an old rule of thumb using a nickel and dime. If the air gap is thinner than a dime, it’s too thin. If you find that the nickel easily slides in and out of the air gap, you can bet that the clutch is totally worn out. While this is a simple, quick test, to get the best results, you always want to use the appropriate service information and check it the way the car manufacturer would want you to do it.
In The Clutch
Belt-driven compressors have a magnetic clutch on the input shaft that cycles the compressor on and off to control cooling. If needed, the clutch can be replaced separately. If the compressor has failed, the replacement unit may or may not come with a new clutch installed. We recommend ordering a new clutch if one is not included.
One concern techs have is the issue of replacing A/C hoses following a compressor failure.
Metallic debris that is spewed into the A/C system when a compressor fails can block orifice tubes and possibly damage a new compressor when it is installed. Getting all of the debris out of the system is therefore essential to make sure the new compressor won’t suffer the same fate.
While most of the garbage ends up in the condenser, some can migrate from here to other parts of the system or be thrown backward into the suction hose from the compressor’s intake port.
Serpentine-style condensers with large diameter tubes can usually be cleaned by flushing with an approved flushing chemical. But parallel-flow condensers or those with very small tubes may be impossible to clean, requiring replacement to eliminate possible contaminants.
As for the refrigerant hoses, replacing the suction and discharge hoses should not be necessary, provided they can be thoroughly flushed and cleaned. Hoses that contain mufflers or orifice tubes, however, usually cannot be cleaned and must be replaced. Installing a protective screen in the end of the suction hose that attaches to the compressor and/or installing an inline filter to trap any residual debris that may have been missed also is recommended for added insurance against a future compressor failure. The high-pressure hose is between the compressor and condenser. Late-model vehicles with R-134a A/C systems require “barrier” (nylon lined) hoses with crimped end fittings. Older vehicles with R-12 systems can use unlined hoses with barbed end connections. When replacing A/C hoses, always use new O-rings or seals.
Check The Radiator
Following an A/C inspection of a compressor clutch and compressor that appear to be in good condition, check the front of the condenser for any type of air flow or debris, or anything that would restrict the ability of the air to flow through the condenser and into the radiator. A suitable shop light should be used to visually inspect the radiator and condenser. On most vehicles, this means removing the plastic cowl on the front of the radiator and then looking down in between the components. Any vehicle with more than 100,000 miles on the radiator is a perfect candidate for a radiator inspection and evaluation. If the coolant is excessively rusty or the radiator core is excessively damaged from road debris, it’s time to consider replacing the radiator.
Tech Tip: Continued Inspection — How to Spot the Type of Refrigerant Leak for an Accurate Diagnosis
When diagnosing a refrigerant leak, it’s helpful to know what type of leak is present in the air conditioning system. There are two types of refrigerant leaks — active and passive. An active leak is easier to locate than a passive leak. Knowing the type of leak you’re dealing with will help determine the type of refrigerant leak detection tool to use for locating the leak.
Active Refrigerant Leak
The active refrigerant leak is a continuous leak, so an electronic leak detector will find it effectively.
There are a number of common causes for active leaks in an A/C system that include:
• Corrosion porosity on a refrigerant line, evaporator or condenser
Note: Paint flaking from a steel refrigerant line or condenser is normal and it will occur over time and is not always an indicator of a refrigerant leak. Evidence of oil around the rusted or paint-flaked refrigerant line does, however, indicate that a leak is present.
– A crack in the compressor housing.
– Loose compressor through bolts.
– Compressor shaft seal.
– Compressor body seals.
• Refrigerant line
– Damage from bending a line during a refrigerant system repair.
– An impact that caused the line to become deformed.
• O-ring or sealing washer
– Debris trapped between an O-ring or sealing washer joint or mating surface.
– An incorrect size O-ring or sealing washer used on a joint or mating surface.
– A rolled O-ring.
– A missing O-ring or sealing washer.
• Improperly torqued components
– An over- or undertorqued refrigerant line or component joint or component fitting.
– An under-torqued pressure switch or cycling switch.
– A loose service port cap
• Component casting porosity
– Porosity from an improperly manufactured part, such as the compressor housing or a thermal expansion valve (TXV) body.
• Service valve or pressure switch
– A pintle that is off center and is not seating properly
– A loose valve pintle
Passive Refrigerant Leak
A passive leak is a type of refrigerant leak that occurs intermittently and are caused by changes in pressure, temperature or vibration.
Using an ultraviolet leak detection dye will be more effective at finding the leak than using an electronic leak detector. Depending upon the severity of the leak and the driving habits of your customer, it may require anywhere take from a few minutes to a few days to locate the leak. Before adding additional dye to the system, Check if it has dye installed from the vehicle manufacturer.
The following are some examples of how a passive leak can occur:
– Expansion and contraction of an under-torqued refrigerant line, component joint or component fitting during operation of the air conditioner.
– Compressor shaft seal leak.
– A cracked braze on a condenser or evaporator from a refrigerant line that is not supported properly.
– Compressor body or front head O-ring.