Proper operation of the A/C and cooling system is critical - Techs must walk the line to meet emissions and fuel economy standards in today's A/C service. - Motor Age - Automotive training, certificat
Proper operation of the A/C and cooling system is criticalTechs must walk the line to meet emissions and fuel economy standards in today's A/C service.
Publish date: Apr 1, 2009 By:Peter F. Meier Source: Motor Age
When you think of drivability issues, the proper function of the A/C and cooling systems is probably the last thing on your
mind. In addition, global warming is one of the "hot" issues of our day, and refrigerant emissions — both direct and indirect
— are coming under increased scrutiny by a variety of regulatory agencies. This month, we'll take a look at just a few of
the concerns you may find showing up in your shop and some keys to staying in line with regulations while servicing customer
complaints.
The Cool Side
A/C compressors can put a large load on the engine when engaged. That robs energy that otherwise could be used to drive the
wheels and impacts fuel economy and emissions. The focus on newer cars is more efficient compressors, controlled more precisely
by the Engine Control Module (ECM). The design goal is to maintain more consistent temperatures at the evaporator.
Pressure switches on many models are now pressure sensors, providing more precise feedback to the ECM. Because any control
module needs accurate feedback to do its job, making sure these sensors are functioning properly should be included as part
of your system diagnosis.
Heating Up
TECH TIP: It has been reported that shorted pressure sensors sharing a common reference voltage with other engine management devices
like the Throttle Position Sensor (TPS) can result in a "no start" condition on some GM models.
TECH TIP: Some hybrid owners may complain of lower fuel economy during the dog days of summer. They may be running their A/C systems on MAX. Doing so can override the "idle stop" feature and keep the Internal Combustion Engine (ICE) running, resulting
in higher fuel use.
Refrigerant emissions also are under fire. The European Union has banned the use of R-134a in any new model platform offered
for sale starting with the 2011 model year. Here in the U.S., Minnesota is the first state to require OEMs to provide information
on system leak rates starting with the 2009 model year. That information is posted on a state Web site for consumers concerned
with global warming for comparison ( http://www.pca.state.mn.us/climatechange/mobileair.html).
There was even talk of an A/C system leak test becoming part of California's emissions inspection, when leaking systems failed
that inspection. Modern A/C systems are using smaller refrigerant charges and fewer connections to reduce these leak rates.
The old days when a compressor shaft seal could leak ½ ounce a year and be considered normal is now the total annual leak
rate from the entire system on some models!
TECH TIP: There are models currently in production using charges of less than 1 pound of refrigerant. That means less room for error
when recovering and recharging these systems, and the need to make sure the system is "tight." New Society of Automotive Engineers
(SAE) standards are in place for both RRR (recovery-recycling-recharging) machines and leak detectors.
Peter Meier is an ASE-certified Master Technician, member of iATN and full-time tech in Tampa, Fla. His experience reaches back over 30 years, and his contributions to Motor Age reflect a wide variety of experience with almost every make and model.
Articles by Peter F. Meier
