Sure, you’ve fixed the car. But today’s A/C-dependent consumers need their air conditioning, too. And not repairing it properly is a BIG mistake.
It used to be that air conditioning, cruise control, power windows, power seats, power mirrors and other similar items were considered accessories or creature comforts in an automobile. Today, however, if the vehicle doesn’t have these, it’s considered undesirable. In fact, not having them even lowers the vehicle’s book value – rather than their being considered add ons.
Because of these societal changes, you need to make these systems functional following a collision – or the vehicle’s owner and his occupants certainly won’t survive a trip across town, let alone cross country.
To help you help them, let’s examine A/C systems, repairs and servicing concerns common to the collision industry. Our first step? Making a determination.
When a collision-damaged vehicle requires servicing of the A/C system, you need to determine the state of charge in order to develop the correct service plan. The system is generally going to be empty or fairly fully charged, if it was functioning prior to the collision. Let’s take a look at both scenarios – and their corresponding service plans. When working with a charged system following a collision, following the proper procedures will minimize your efforts:
1. Sample the contents. You’ll need to discharge the system before disassembly. Use a refrigerant identifier to sample the contents of the system to determine that it contains the proper refrigerant type before hooking it up to A/C service equipment.
These units can also provide the percentage of atmospheric gases in the refrigerant, which can’t be above 2 percent for proper performance. Some of the identifiers have the ability to purge the atmospheric gases from the vehicle system before recovery operations are performed by the service. Failing to purge atmospheric gases can cause them to end up in the storage tank of the recovery equipment.
Some recovery equipment is capable of purging atmospheric gases from their storage tanks, while others require hooking the identifier to the tank, sampling the tank contents and purging the tank if necessary. Refrigerant identifiers are beneficial because they identify system contents and clean them of atmospheric gases.
These same identifiers can also be hooked to the storage tank to check it for contaminating gases. If atmospheric gases are present in the tank, the units that are able can be used to purge the air from the tank. Some A/C service equipment used by shops have the capabilities to purge the tank of the air – and some don’t.
2. Discharge the system. Once identification is done, discharge the system and document the amount of refrigerant captured. You should also document for later use any oil that leaves the system with the recovered refrigerant.
3. Take apart the fittings. Once you’ve discharged the system, take apart the fittings so you can remove the desired components. It’s important at this point to identify the locations and direction of installation of all gaskets and o-rings for later assembly.
4. Secure new o-rings and gaskets. Using the old ones for sizing, secure new o-rings and gaskets. Replacing these will greatly help to prevent leakage problems following recharging. The o-rings and gaskets take a foot print when the fitting is tightened and are difficult to position exactly the same during reassembly.
5. Seal off open lines or components. Do this shortly after removing them to keep the three enemies of the A/C system out: dirt, moisture and air. Sealing off the components doesn’t mean putting masking tape or duct tape over the fitting or opening. The openings need to be sealed tightly. This requires using tight-fitting rubber plugs; caps with o-rings secured from previously replaced parts; small, tight-fitting balloons; or other similar methods that won’t allow any air in or out. Doing this protects the system and can allow the filter/dryer to be reused if the system contained a charge when taken apart. (I’ll cover the filter/dryer and concerns regarding its replacement later in the article.)
6. Perform vehicle repairs. Once you’ve finished the structural and body repairs, you can complete the A/C system assembly and service.A system that enters the shop already empty and open to the atmosphere requires different considerations in regard to service plans and parts requirements. If the system is empty, it’s likely that it’s become contaminated by those three enemies of the A/C system. This affects parts considerations in regard to the filter/dryer unit.
If the unit has been exposed to atmospheric gases for a prolonged period of time (a matter of one to four hours or more, depending on humidity levels), it’s best that you replace it. OEM procedures recommend this because of the desiccant material that’s in the unit to absorb moisture from the refrigerant. If it becomes saturated with moisture contained in the atmospheric gases, it won’t be able to perform its job correctly. Over a period of time (several months), this moisture will react with the soft aluminum parts of the system and form an acid type of sludge inside the system. And this will potentially damage the compressor or cause pinholes in lines and components.
System oil capacity is also up for grabs with a system that’s ruptured or leaked out. It’s common to utilize charts for oil amounts when you’re replacing components in a system that was discharged following recommended procedures. Charts are provided in service data from OEMs and/or aftermarket suppliers of service manuals and electronic databases. A/C system material suppliers oftentimes have manuals with similar information that a jobber can provide to the shop.
With a system that ruptured during a collision, the amount remaining in the system is somewhat unknown. You could chemically flush all remaining components, remove and drain the compressor, replace the filter/dryer and hope to get back close to a zero starting point for refilling. This, however, requires taking apart almost every fitting – meaning you’ll need to replace all o-rings and gaskets.
But you can’t flush a compressor or filter/dryer. It’s also difficult to get all the oil out of the evaporator core and condenser cores. What you can do, oftentimes, is use charts based on recommendations for the oil amount for the replacement part, and add some additional oil (best guess) for the oil lost due to the fast discharge during rupture of the system.
Another consideration is if the system did rupture, are the surfaces coated by the oil that escaped? These are generally going to be in the engine compartment. And if they’re not degreased through detailing procedures, the oil will gather or collect road grime and act as an insulation blanket. This can cause components to overheat and parts to fail prematurely.
If openings to the system have become contaminated by dirt and fluids, these parts will likely need to be chemically flushed with the proper equipment. This equipment also needs to be compliant with the laws regulating A/C service procedures.
If a part is contaminated and can’t be flushed, you’ll need to replace it – for example, the filter/dryer unit or refrigerant flow-control devices. Seal all openings just like with a system that was charged when servicing began. The reason for this is to prevent any additional contamination from occurring.
Don’t put new filter/dryer units in the system until just before performing recharging procedures. New parts should come sealed with plugs to prevent contamination. Don’t remove these plugs until just prior to their installation, particularly with filter/dryer units. (Save the plugs to use when servicing systems in the future.)The items and concerns we’ve covered so far are things that need to be communicated to the A/C service person who’ll recharge the system. He needs to know what he’s dealing with.
He needs to know how the system got discharged and what the potential is for contamination. He also needs to know what parts have been replaced, such as o-rings. This will help him to determine how much refrigerant oil to add to the system.
The A/C person can be a sublet person, a mechanical person for the collision facility or a body tech who does the A/C for the shop – but there’s usually a specific person responsible for the A/C recharge. Many of the parts would be installed during assembly of the front end if a core support, radiator and fan are involved. Most body techs are going to want the flat rates to hang the parts and cannot wait to have a specialist bolt-in the items they’re capable of doing. This is why it’s important for communication to take place between the person hanging the parts and the A/C service person. Many times, the same specialist would also do the discharge procedures, if required. These specialists are commonly in-house at larger facilities.
The oil used in the A/C system is one of the most refined and pure types of oils used in automobiles. With R134 refrigerant, there are multiple specifications for the oil type. The correct specified oil needs to be used so the compressor will be properly lubricated and have maximum life.
But securing these specifications can sometimes be a challenge. In many cases, system capacity and OEM specified oil are more readily available than the aftermarket oil part type. This means you (or whoever your shop’s A/C service person is) may need to cross an OEM part number over to a PAG oil type that’s used to identify different oils. In some cases, the OEM part number oil is available from the dealer and might be color coded for identification.
Next, put the oil that needs to be added to the system in components that were replaced or flushed. If the compressor is drained, add the proper amount so it’ll have lubrication right away when cycled on. Only about half the oil is at the compressor at any point in time. The remaining portion moves with the refrigerant throughout the system. If all of the oil arrived at the compressor at startup, damage could be done to the compressor. That’s why oil needs to be in the various components according to system-capacity charts by components.After you’ve put the system back together and installed the proper oil type and amount, evacuation is your next step. This procedure requires using a recharging station that has a vacuum pump.
After making sure all lines and fittings have been properly tightened, hook up the equipment to the vehicle’s service ports. Follow the equipment steps to enter the evacuation mode. You should set this for a five-minute period, during which you observe the vacuum gauge to see if the needle goes to the proper measurement – somewhere between 29 to 30 inches of vacuum, depending on your elevation relative to sea level.
Once the five minutes are up, observe the gauge over the next five-to-10 minute period to see if it creeps back up toward zero. Any movement on the gauge is an indication that the system likely won’t hold a charge due to a leak.
If you detect movement, recheck all fittings to make sure they’re properly tightened. If you re-used any o-ring rings or gaskets, they now become suspect as to the cause of this leak. And if you can’t get the system to hold a vacuum, it won’t hold a charge. Keep in mind the equipment being used could also be the cause of the leak. Check all fittings on the equipment if need be.
Once it’ll hold a vacuum, set the timer to evacuate for a minimum of 30 minutes. (Longer won’t hurt the system.)
What the evacuation process does is remove all gases from the system. But evacuation won’t remove solid particles or liquids. That’s why dirt needs to be flushed from parts before reassembly. It’s also why the oil can be put in the system before assembly. The reason for the 30-minute minimum is that placing a vacuum on the closed system lowers the boiling point of water from 212 degrees F to below room temperature of 70 degrees, depending on your elevation relative to sea level. This requires a vacuum of greater than 29 inches (but we’re only talking about tenths and hundredths of an inch greater).
With the vacuum on the system, the moisture that might be in the system comes to a boil and changes from a liquid to a gas. Once it’s in gas form, the vacuum can then remove it from the system. Anything less than the recommended 30-minute minimum might not remove all the moisture. Longer than 30 minutes will help ensure that moisture is removed.You need to know the proper charge amount for the system being recharged. Once the vehicle’s specification is sourced, today’s charging systems make recharging more simplistic.
You also need to know the quantity of refrigerant to be added to the vehicle specification to compensate for the service lines used to hook the equipment to the vehicle. If you don’t compensate for this, the vehicle system will be shorted the amount in the service hoses and likely won’t work at peak performance. This information should be listed in the equipment operation manual.
But the job isn’t done once the system has the proper charge in it. Simply starting the vehicle and turning on the A/C system to see if it blows cold air doesn’t mean it’ll work at a later date or on a hot day at peak demand conditions. The recharging steps need to be followed by leak-detection methods and performance testing. Leak-detection methods and tools need to be understood clearly to get accurate results. A variety of methods and tools are available. The most common method and tool used today is likely the electronic leak detectors. Each brand and model offers slightly different features, but all work relatively the same. With refrigerant in the system, turn on the detector and allow it to stabilize. Select and match the correct scale setting to the refrigerant type in the system if the tool has multiple refrigerant capabilities.
Once you set the detector, slowly move the wand or detection piece along the system lines and components. It’s important to understand that refrigerant gases are heavier than air and will be most easily detected by moving along the bottom side of a line or fitting. When checking the condenser, make sure to work the lower radiator core support area thoroughly, since leaking refrigerant is likely to gather there.
Check all seals, fittings and areas of the compressor that could be the source of a leak. If the system is running while you’re doing this, be careful of moving parts and hot items.
Even if you detect no leaks, remember to check the service ports once you disconnect the service equipment to ensure they’re sealed tightly.
Doing the leak detection while the performance testing is being done allows both time for the system to stabilize and the high side of the system to reach operating pressures that are more likely to show the leaks. Checking the low side before starting the engine will place higher pressures on the low side of the system than when it’s running.
You can also use soapy water on fittings and areas you suspect have leaks. If a leak exists, bubbles will form in the area of the leak. This is similar to checking for leaking valve stems on a tire. You wouldn’t do this to check the entire system, but rather to check specific areas where you may be having trouble with conventional leak detection methods.
Also, ultraviolet dyes are available to add to the refrigerant charge, enabling you to use a black light to look for the area of the leak. Keep in mind that, if added, the dye will be in the refrigerant and will be an identifier that the system’s been serviced. Some OEM manufacturers may advise against the use of these dyes, and their use may void the warranty.
Also keep in mind that if the refrigerant is recovered into the equipment, it’ll contaminate all the refrigerant in the equipment’s storage tank.Performance testing is a big part of the documentation of the repairs. Fill out A/C service forms to document what’s been done to the system, the amount of oil and refrigerant added, system operation pressures, temperature and humidity at the time of service, duct temperatures achieved inside the vehicle, the servicing technician’s name and other information important for the file. This can all be very helpful if a system comes back at a later date because it isn’t functioning.
Specifications for performance testing needs to be secured for the type of system, compressor type, control device type, and temperature and humidity readings in order to know if the compressor is cycling in and out correctly.
Measure the temperature inside the vehicle in the center duct of the dash to determine if the outlet temperatures are getting down to the proper readings, based on the ambient temperature and humidity at the time of the testing. The system must be stabilized to take these readings. This means that the vehicle and A/C need to be running for several minutes and that the engine RPM must be at the specified reading according to service procedures.Hopefully I’ve defined the steps and procedures that everyone in the collision industry needs to know to understand the requirements of collision A/C servicing. Certainly, the actual service work involves a much more detailed understanding to be able to perform it. Also, I didn’t address the electrical side of this issue, which can affect the workings of the A/C system.
Still, estimators and collision technicians need to understand these basics to ensure they make the right decisions and communicate properly as vehicles are moved through the repair process, sent to the A/C service person and, ultimately, returned to the customer – whose car isn’t really “fixed” until the A/C works, too.
Writer Tom Brandt is an autobody collision technology instructor at Minnesota State College Southeast Technical Campus in Winona, Minn. The program is a post-secondary, two-year diploma program and is NATEF certified. Brandt has 16 years of teaching experience, has been an I-CAR instructor for 15 years and, prior to that, was a combination technician.