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30 Sept. 2009
Airconditioning equipment technology.
Ecotechnics service equipment pre-delivery service in progress at AECS.
AECS as a training institute and equipment providers comes across many misconceptions about air conditioning. In this article I would like you to take a fresh look at some of the aspects of aircon service.
In my view is the role and profitability of regular automotive aircon maintenance totally under-estimated by most automotive technicians out there.
I believe that as a tutor I have to try to change this.
Aircon systems leak.
As a result of inevitable leaks on any automotive air conditioning system of any brand, the aircon system can cause high fuel consumption and is in danger of expensive damage after having been intensively used for about three years without service.
Why do we get our customers to come in with their cars for a regular services? To change oil and filters, and to check a number of items on the vehicle. Hardly any garage seems to ever service an aircon system as part of a regular service. Therefore all systems wait for expensive terminal failure, which ends up not being repaired on most vehicles as a result of the very high costs.
Yet aircon service is so simple and so profitable! As long as you have the right equipment and knowledge.
Some garages (and even airon specialists?) are dabbling around with a gauge set and a separate compressor and feel that they are totally ready for aircon service.
Pls let me layout what you need for proper aircon service and motivate the components technically:
Connect to the vehicle
You need hoses, couplers and a gauge set with manifold to connect to the aircon system’s quick couplings.
Ecotechnics gauge set
Often these gauges are used for diagnostics without the operator realising that by simply connecting they are altering the system’s charge. Alternative for quick diagnostics are tools with pressure sensors which cannot alter the system’s charge.
The Sherlock, Ecotechnics quick and portable aircon inspection tool
Evacuate (remove) the refrigerant
You need to be able to evacuate the refrigerant from the vehicle into a storage bottle.
Evac pump and waste bottle
Often the used refrigerant (with the PAG oil) gets pumped straight into a waste bottle for it to be destroyed by a company like BOC gas, yet the refrigerant does not lose it chemical composition unless it is mixed with blend gasses.
The best practice by far is to recycle the refrigerant, by filtering, distilling and de-acidising it, making it ready for re-use.
Ecotec ECK recycle and recovery (R&R) machine with distillation towers and filters.
The distillation columns besides separating gasses, separates the oil which inevitably escapes together with the refrigerant. The oil volume needs to be measured and visually inspected for discolouration. The quantity needs to be measured as the system does not have a dip stick. “The quantity which comes out needs to go back in!”.
Inspecting the colour of the oil is important as it is an indicator of what kind of mechanical strain the compressor has had, and if it makes sense to recharge the system.
We don’t need come backs in our workshops!
Contaminated PAG oil from a system with a worn compressor.
The oil reintroduced into the system needs to be of suitable viscosity (three different types) and from a closed airtight container.
The quantity of recovered oil varies greatly from service to service even on the same vehicle.
Best practice is to measure the quantity recovered by for example weight. Store the recovered oil in a clear bottle and automatically reintroducing the same quantity of new oil in to the vehicle.
Three different viscosities PAG oil bottles. These oils are chemically single capped (non Daphne).
Vacuumise and leak check the aircon system
The next thing you need to connect is a vacuum pump, the vacuum pump needs to draw any remaining gasses out of the system, including possible water vapour. The vacuum pump needs to be serviced regularly, of which a service record needs to be kept. The vacuum pump needs to be connected to the vehicle through a gauge set, just like the evacuation compressor.
Ecotechnics vauum pump with gauge set.
The vacuum stability needs to be checked, to ensure that no vacuum leak is present wasting the refrigerant which is to be charged into the system. After a period of vacuum time you need to switch the pump off and monitor the gauges for some time to see if the system has a leak.
Best practice is that the vacuum leak check on the vehicle gets performed automatically and that vacuum pump unit automatically indicates that it is in need of maintenance.
After the vacuum leak check a Nitrogen pressure leak check can be performed automatically, if that option has been bought with the R&R unit.
Ecotechnics ECK R&R unit’s vacuum pump.
Charge (refill) the system
After the system has passed the (vacuum) leak check the system needs to be recharged, for this purpose the vacuum pump (and gauge set) needs to be removed and a bottle with clean pure refrigerant needs to be connected. The operator needs to check in a data base how much “gas” the system needs and has to precisely meter this out….
For this purpose the operator needs a set of electronic scales, one which records the weight before and after the charging process. When the desired weight of refrigerant has been introduced into the system the bottle need to be closed, manually or automatically by a set of extra solenoids which can be purchased with the scales.
There is no way that on modern systems with only 500 grams (+/-10 grams) of R 134a the charge quantity can be guessed by ‘feeling the tubes’. This almost certainly will end up in expensive aircon failure.
Ecotechnics electronic scales.
Best practise is that the machine has a data base which contains a charge quantity table, of which you only have to select the vehicle model and age. After which the machine automatically meters out the correct amount of refrigerant.
Ecotechnics ECK 3900 (2010 model) fully automatic recovery/ recycle system.
Charging can be done with liquid or gaseous refrigerant. An operator with lose service components needs to think about this.
Best practise is a machine with solenoid valves which will automatically select liquid on the high side and gas on the low side. On such a machine the pressure difference during charging is created by a heater blanket around the on board refrigerant bottle, which turns on and off automatically. A heater blanket speeds up the charging process dramatically.
Picture heater blanket inside the ECK.
Nitrogen pressure leak tests or diagnostics through logic can also be performed by such machines, something which is very time consuming with manual equipment.
For high volume aircon installations like busses the refrigerant needs to be positively charged in to the vehicle, for this purpose a separate high volume charge compressor is build into a truck designated unit, this is needed for systems where more than approx. 1.5 Kg’s of refrigerant is needed.
ECK truck with high volume components and positive pressure R134a charging pump.
Equipment knowledge
On all aircon recovery systems high pressure condensable gasses (incorrectly called non condensable gasses) get introduced into the recovery tank, increasing the pressure of the tank.
On a manual system (loose components) the pressure of the tank and its temperature needs to be measured, to work out with a chart if the high pressure condensable gasses are slowing the recovery process down. Sometimes bringing it to a halt, damaging the recovery compressor.
Best practise is to have the logic (electronics) in the machine deciding if these gasses are present and then have the machine automatically purging these gasses out of the on board tank. This automatic process eliminates the chance of refrigerant entering into the atmosphere.
Environment
The Ecotechnics equipment from AECS Ltd are as one of the few suppliers homologated in the USA market under the strict new no loss SAE standard SAE J-2788. This Jan 2008 standard specifies the machine’s precision with regards to the loss of refrigerant during the recovery/recycle procedure and the precision in charging volume. This is in line with the IRHACE’s voluntary NZ guide lines.
Summary
To set up for airconditioning service there are several items which are essential. The purchase figures used are indicative and vary from equipment brand to brand.
Manual (lose components)