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You will never see
us arriving
at a job sight
loaded with
5 gallon buckets
of rusty tools
attempting to
"wing it"

— Mark Armstrong


 

Air Conditioning

 

At Mobile Diesel Medic we bring out a complete professional air conditioning recharge diagnostic station to your job location.  There is so much to doing air conditioning right.  One needs to make sure when you recharge your system with new refrigerant, it remains in your system.  Here at Mobile Diesel Medic we test for leaks on all recharge jobs before we add refrigerant to your system and not after the customer returns complaining the AC recharge only lasted two weeks.  Whenever we change any components in your system, we always flush all debris and contaminants out prior to addingnew parts.  Whenever changing new parts, all jobs will always include replacing expansion valves, orifice tubes, receiver dryers, and accumulators. They don’t cost that much, why be penny wise and pound foolish.

There are so many different mixes of environmentally friendly refrigerants that some are not compatible with earlier less efficient versions.  When servicing your Air Conditioning system, we always come out with a top end gas analyzer to get a confirmation of purity of refrigerant prior to adding anything.  This ensures no cross contamination.  Once your system is contaminated, it is nearly impossible to bring back to original.  Finally when exposing AC hose ends, compressors, dryers, evaporators, condensers and any other A.C. components to atmosphere, your air conditioning system will never work at its optimal best if any moisture is left behind in your system.  When we drive out to your job sight all Air Conditioning Services, always include the evacuation of all water in the system before adding the refrigerant.  This takes an extra half hour but the benefits far outweigh the labor cost.

Air Conditioning 101

  •  HVAC – Heating Ventilation Air Conditioning.  Heating and air conditioning is supposedly one discipline but the reality is in the automotive world it is 96% AC and the remainder is heater blend doors and leaky cores etc…
  •   New Computer Controlled AC systems – Lots of newer air conditioning systems communicate via an ECM.  The systems are no longer isolated and separate from the rest of the motor..  This is frustrating for the do-it-yourselfers, but the benefit is by incorporating electronics into the mix, many newer fuel saving strategies have come on line.
  •  Vacuum Testing – Can’t say enough good things about our handy vacuum pumps/leak testers.  They make sure your systems are leak free and won’t dump all your nifty new refrigerant in one week, as well it flashes all unwanted moisture out of your AC piping and arteries.  Remember water good in heaters and water BAD in Air Conditioning Systems
  • AC Flushing – Lots of solid and gooey contaminants via too much water, happens when those small disposable quickie ac recharge kits are used without proper pulling the water out of your system before recharging it.  Those too good to be true cheepo kits mostly wreak havoc on the fixed spray points of the Orifice Tubes and the Expansion Valves.  When we can’t get communication between the high side and low, we flush.  That usually does the trick.
  • Receiver Dryer- Older technology than the Accumulator but works great and has a water removing desiccant bag that keeps the moisture to a minimum.  When this thing gets gooey inside it releases contaminants that clog small pinhole passage-ways like in the expansion valve.
  • Expansion Valve – This is also older technology but has a variable orifice aspect to it that reduces the load on the compressor when not so hot outside.  This saves fuel and therefore Expansion Valve platforms are making a comeback.  You will find them in higher end systems as well as bigger trucks
  • Compressor – This guy combined with the Condenser and Evaporator almost feels like an accordion performance on the Lawrence Welk Show.  Yes my grandmother forced me to watch it with her on Sunday evenings.  The Compressor pulls (stretches) cool liquid refrigerant into a cooler gas, and pushes (compresses) hot gas back into a hotter liquid.  Really quite exiting, almost as exciting for me as Sunday evenings with Mr Welk was for my Grandmother.
  • Condenser – Takes a too hot to handle gas refrigerant (most likely R134a) and pounds it into submission.  As long as you have enough refrigerant in your system the Condenser zone will be the area that the hot gas gets condensed back into a liquid.  But you gota have the juice or forget about it. Any low levels on Refrigerant it will stay a gas.
  • Evaporator – This is where the magic happens.  Found in your hot dash board, it miraculously pours oh so cold air into your little mobile eco-system.  The Evaporator receives a fine misty cloud of small refrigerant droplets and flashes them into a gas.  The spray of refrigerant won’t occur if it is submerged due to too much refrigerant.  Too much juice no magic cooling box.  Worse yet your compressor will take a dump on you.  You better not overcharge your system with one of those lame all in one kits.
  • Presser Switch – Don’t bypass this switch.  If your pressure switch is stuck on without much refrigerant, it will cause the system to run empty.  This is bad, kind of like running a transmission without any ATF.  Causes damage but not quite as sudden and catastrophic as running a motor without the motor oil.  None the less permanent and expensive.  Pressure switches are designed to shut the whole system down to save you money and heartache.
  • Accumulator / Dehydrator – This guy has a nifty way of gathering up all the liquid refrigerant and keeping it separate from the gas.  Compressors absolutely don’t like compressing liquid and a properly functioning accumulator keeps the compressor happy.  Always found with Orifice Tubes.
  • Fixed Orifice Tube (FOT) also called the expansion tube. Don’t want this guy clogged with contamination.  It needs to make a fine spray.  Its purpose is to make small droplets of refrigerant from large droplets.  It’s much easier to flash a small droplet into a gas than a big droplet. Always found with Accumulators
  • R-134a refrigerant – This is the bread and butter refrigerant found in all new automotive applications.  Rumor has it new refrigerants are “right around the corner,” but this is only on a flyer on my desk which creates fear in me and forces me to pay for five class spots in next month’s HVAC update class.  Got keep the money local and flowing right?
  • NU-R22b refrigerant – Truly bad #ss refrigerant, usually found on larger passenger/tour busses or on yachts.  Much Much cooler than the R-22a!!  It has the same high efficiency cooling capabilities of the old R-22 with all the safe environmental aspects of the R-22a. Prevents both the lefts and rights from getting hot and bothered.
  • High Pressure Side – Goes hotter when the compressor forces the gas back into a liquid
  • Low Pressure Side – Goes colder when pulls liquid into a gas.  Arteries can’t be clogged or none of this will work efficiently.

Photography: © Jessica Armstrong 2013

we do air conditioning throughout the sf bay area

san francisco • oakland • san jose • san mateo • south bay • marin • san rafael • north bay • east bay