Avoiding diagnostic traps

With all the electronic controls on today’s systems, it’s awfully easy to fall into the trap of looking for responses to them and letting those responses color our diagnostic thinking. The dual system on a 2003 Land Rover Discovery seemed to fit into that category. It switched from hot to cold and cold to hot nicely on the driver’s side, but seemed to be stuck in hot on the passenger’s side. So the technician started to think “electronic controls” and began digging into the HVAC case, first disconnecting the motor to see if he could hear any difference. He couldn’t, and he was next going to head for the heater, first hooking up the recovery machine so he could disconnect the evaporator, when another technician (who hadn’t settled into a particular line of thinking), said to do an evac and recharge. By this point, you’ve probably already figured out that the problem was just a low charge – about 12 ounces low on a 32-ounce system.


The “second opinion” is standard procedure for complex medical procedures. It’s always worthwhile getting one before you dig too deep into an automotive system unless the problem is very well defined. Much of the time during the heart of the A/C season, the shop is too busy to post the question at an online forum and wait for answers (although many technicians do, and are surprised at how fast many technicians respond). However, talk to another tech in the shop, another shop with which you have a friendly relationship, or look at a diagnostic chart or an on-line system like Identifix—just get that second opinion.

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit http://bit.ly/10zvMYg for more information.

You can E-mail us at macsworldwide@macsw.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Mobile A/C The Next Generation, February 11-13, 2016 at the Caribe Royale, Orlando, FL.

About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues. www.macsw.org
This entry was posted in ACtion Magazine, aftermarket career week, Automotive, Automotive Aftermarket, Automotive training, MACS Member, MACS Training Event, Mobile Air Conditioning, Refrigerants and tagged , , , , . Bookmark the permalink.

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