The Tiniest Mistake

Is faulty HVAC diagnosis costing you money in the cold of winter?

Sometimes the tiniest mistake can be very costly. Take the heating, ventilation & air conditioning (HVAC) system: like the tires or the brake lines, it's one of the systems on a vehicle where a flaw no bigger than a pin prick, gone unnoticed, can cause utter disaster.

Paul DeGuiseppi, manager of service training for the Mobile Air Conditioning Society (MACS), has seen a lot of tiny mistakes become major problems in his day.

"Technicians are making mistakes--we even have a published list of the top 11 mistakes they make--and it's because of a lack of knowledge and lack of training," he says. "There's this attitude of 'That's the way we've been doing it for years,' and that's the main thing I see. Other things I hear: 'It worked on my '82 Monte Carlo...' 'That's what the salesman told me would work...' 'The label on this container says...' All those kinds of things."

It's enough to make a professional trainer pull his hair out. But, because every technician who works with refrigerant is required by the Environmental Protection Agency (EPA) to be certified, DeGuiseppi keeps on hammering home his message, in class after class.


Of course it makes perfect sense to talk to an expert about air conditioning when winter is approaching.

"Based on the fact that you're using your air conditioning for window defrosting, you should absolutely pay attention to it in the wintertime," DeGuiseppi says. "You also have to apply the same maintenance list to the cooling system. Cooling systems and A/C systems are very interrelated. The belt that spins the compressor is often the same belt that spins the water pump. The cooling fan that comes on when you turn the A/C on is the same cooling fan that comes on when the engine reaches a certain temperature. And of course, the cooling system is important in wintertime for heating purposes.

"Keep in mind that at around 35 or 38 degrees, the compressor will not engage anyway, and that's for two reasons," he explains. "One: they don't want the compressor operating at such low ambient temperatures, because that could damage the compressor, due to the fact that the oil is thicker, so it might not receive adequate lubrication. The second reason is, it's really not needed, because the colder the air is, the less humidity it contains, but when the compressor runs it dehumidifies the air, and the dehumidified air just does a better job of clearing the windshield.

"A diagnostic process that many technicians will use is, if they have a lack of compressor clutch engagement, the first thing they'll do is turn the controls to defrost," he explains. "If the compressor does not engage, they know they need to start digging."

Unfortunately, many technicians don't know where to start digging, because their training isn't up to snuff, according to DeGuiseppi.

What's missing?

"Basically, not staying current with things that are happening, or have been happening, with air conditioning," DeGuiseppi says, "like smaller charge systems, understanding why it's so important to recharge with incredible accuracy, maintaining the equipment to help you do this the right way.

"A lot of people don't understand this: many old systems held three pounds of refrigerant; some today hold less than a pound," he explains. "You have to be much more accurate on these tighter systems, because the tiniest mistake can cause it to blow too warm or damage the compressor or many other things. But basically, repeat compressor failures, when they're swapping out compressors and other components, means they're not doing the full job, not doing the job the right way."


"The biggest issue is leaks," says William Johnston, climate control manufacturing & service manager for Ford Motor Company. "We struggle with the technician's ability to properly identify a leak. In response to that, the SAE has recently developed new standards for leak detection tools and refrigerant recovery/recycling machines.

This content continues onto the next page...

We Recommend