Underhood: Timing The BMW N53 And N54
Adapted from Larry Carley’s article in TechShop
Like any type of service equipment today, refrigerant recovery equipment must be fast, accurate, easy to operate and provide a good return on investment. What’s more, it must also meet certain legal requirements. You may already have used A/C recycling and recovery units in your automotive classes. Or you may not use one until your first job in a shop. Whichever the case, knowing why to use this equipment is just as important as how to use it.
Why Recover & Recycle?
The Environmental Protection Agency (and just about everyone else, for that matter) does not want technicians venting refrigerant when servicing vehicles. For many years, this was a common practice because refrigerant was relatively cheap and no one realized it was causing any harm. Today, R-12 (used in older vehicles) is scarce and expensive, and we know it is harmful to the environment.
Recovery equipment is readily available from a variety of aftermarket suppliers, so there’s no excuse not to recover the old refrigerant before you work on a customer’s A/C system. In fact, it is illegal to vent any type of refrigerant from a vehicle, including R-12, R-134a (used in newer vehicles) or any other alternative or unknown refrigerant. The prohibition against venting includes even a small charge of refrigerant that may have been added to a vehicle for purposes of detecting a leak. If there’s any refrigerant in the system at all, it must be recovered and not allowed to escape. Period.
Venting has been outlawed because man-made chlorofluorocarbons (CFCs) such as R-12 damage the Earth’s protective ozone layer that shields us from most of the sun’s harmful ultraviolet radiation. Scientists have discovered that CFCs react with ozone in such a way that ozone is destroyed faster than it can be replenished by natural processes. The result has been a measurable thinning of the ozone layer and a big increase in UV exposure, which increases the risk of skin cancer.
To make matters worse, CFCs break down very slowly. R-12 is estimated to have an atmospheric lifespan of nearly 100 years! So any R-12 that leaks out of a vehicle’s A/C system today will still be eating holes in the ozone layer a century from now! That’s why recovery is so important.
Reducing global warming is another reason not to vent refrigerants. R-134a contains no chlorine and poses no danger to the ozone layer, but like R-12, it is a “greenhouse” gas that retains heat and contributes to the global warming problem. The “Global Warming Potential” (GWP) rating of R-134a is 1,200, which compares to 7,300 for R-12, but only 1.0 for carbon dioxide. So every pound of refrigerant that leaks or escapes into the atmosphere has the same effect as thousands of pounds of CO2.
Refrigerants are also a valuable commodity that can be easily recycled and reused. R-12 is getting hard to find these days and costs a fortune. Why let it escape if you can easily and inexpensively recover it, recycle it and then resell it back to your customers?
What To Expect
The type of recovery and recycling equipment that you will use will depend on the volume of A/C work performed at the shop where you work. It also may depend on the shop owner’s budget. You should note that these units can cost quite a bit of money, so make sure you use them properly. A shop owner can’t go around replacing expensive service equipment if his employees are mishandling the machines.
Basic recycling equipment generally costs anywhere from $3,000 to $4,500 or more, which isn’t a bad deal considering the equipment can pay for itself in six months or less depending on the volume of A/C service work a shop does. If your shop attempts to go for a faster payback, it may charge a “cleaning fee” for recovering and recycling your customer’s old refrigerant.
Some recovery and recycling machines have a built-in refrigerant identifier. This feature is highly recommended to prevent accidental cross-contamination of refrigerants, as well as the equipment itself.
There is no way to know for sure what kind of refrigerant is actually in a vehicle or if it has been cross-contaminated without testing it. An identifier will tell you what’s in the system and its degree of purity. Most will also detect flammable hydrocarbons such as propane or butane that can be hazardous to technicians. If the identifier detects the wrong type of refrigerant or a flammable refrigerant, it stops the recovery process and warns the operator.
The law requires a separate recover and recycling machine for each type of refrigerant you service: one for R-12, one for R-134a and a third machine if you work with any alternative refrigerants. To keep costs down, some suppliers offer “combination” recovery and recycling machines that can do both R-12 and R-134a using separate internal circuits, pumps, filters and storage tanks. Some of these machines have two separate compressors while others share a common compressor and use a self-cleaning purge cycle to prevent cross-contamination of refrigerant lubricants.
Purity standards are also important. Recycling equipment must meet SAE J1991 for R-12 (no more than 15 ppm moisture, 4,000 ppm of refrigerant oil and 150 ppm of noncondensable gases/air by weight), and/or SAE J2099 for R-134a (no more than 50 ppm of moisture by weight, 500 ppm of refrigerant oil, and 150 ppm of noncondensable gases/air by weight).
If you end up doing a lot of A/C service work at your place of employment, a combination recovery/recycling/charging station may provide the best all-round service solution. Such units typically sell in the $6,000 to $7,500 range. The latest generation of A/C service equipment combines identification, recovery/recycling, vacuum purging, recharging, pressure readings and refrigerant identification into one machine. On the more sophisticated models, most of these functions are automated so an operator doesn’t have to baby-sit the machine while it pulls out the refrigerant and recharges the system. Additional features may include automatic oil purging after recovery, automatic air purging from the recovery tank to minimize the risk of air contamination, and the ability to capture and record important system data (minimum and maximum system pressure, outlet duct temperatures, amount of refrigerant charge in system, etc.), and to generate a printed report for the customer.
A highly accurate scale is also essential. Most vehicles today have reduced refrigerant capacity (under 2 lbs.), which means charging accuracy is extremely important to avoid overcharging the system. This requires a highly accurate scale (plus or minus 1 oz.) for measuring the amount of refrigerant used. If you have an older machine that can’t achieve this level of accuracy, it’s time to upgrade to new equipment.
Ready To Operate
Using a recovery/recycling machine isn’t difficult. The basic procedure goes as follows:
- Connect the hoses on the recovery machine to the service fitting on the vehicle.
- Turn the recovery unit on following the equipment manufacturer’s operating instructions. Allow the machine to continue pulling refrigerant from the system until it indicates all of the refrigerant has been recovered (system pressure reads vacuum and holds vacuum for at least 5 minutes). If the machine does not have an automatic timer or shut-off, discontinue recovery at this time, and close and disconnect the service hoses.
TIP: If A/C components show evidence of icing during the recovery process, the components can be gently heated to speed up the flow of refrigerant. Use a hot air blow dryer, never any type of open flame, to heat parts.
Most machines use “single-pass” recycling where the refrigerant makes only one pass through the cleaning circuit, but some machines also offer “multi-pass” recycling or a choice of single-pass or multi-pass cleaning. Multi-pass cleaning takes longer, but may be necessary with refrigerant that contains a lot of moisture.
The filter-drier that removes particulates and moisture from the refrigerant needs to be replaced periodically. Filter capacities vary somewhat from one machine to another, and lifespan depends on how much crud and moisture the filter picks up from the refrigerant. But as a rule, a typical filter will usually clean about 1,000 lbs. of refrigerant before it has to be replaced.