Tech Stuff

Nailing tough A/C problems: A review of new tools and diagnostic strategies

Craig Truglia is an ASE A6, A8, and L1 certified technician who presently works as a service writer for Patterson Auto Body, a repair facility in Patterson, N.Y. A former shop owner and editor of several automotive repair magazines, Truglia combines his Columbia University education with the real-world experience he sees daily in the automotive repair field. Technicians Truglia and Fred Byron took part in diagnosing the different vehicles presented as examples in this article.

As labor rates climb, and serviceability gets increasingly convoluted, it is becoming more and more important to diagnose A/C problems as accurately as possible. Of course, being that air conditioning is generally diagnosed by interpreting pressures and looking at the “general vicinity” of where UV dye can be spotted, it’s less than an objective, exact science.

However, there are new tools and diagnostic strategies that make use of the tools already in most shops, that can greatly increase accuracy in diagnosing A/C problems. Chief among these is using thermal imagers, emissions analyzers, broad spectrum UV flashlights, CO2 gas and a smoke machine, and the Bullseye Leak Detector (which in principle works the same).

This example citing a 1995 Jeep Grand Cherokee has a leaking A/C condenser. The dye, however, cannot be seen on the condenser itself but rather on a nearby area running adjacent to A/C lines that are not leaking. Dye oftentimes nails the spot of the A/C leak, but other times it just tells the technician the general area in which to look. This specific A/C leak was spotted using a Cliplight Vector 7 UV light and dye (A/C Pro Pag 100 with UV dye). It was repaired using sealant (specifically U-View Leak Guard.)
<p>This example citing a 1995 Jeep Grand Cherokee has a leaking A/C condenser. The dye, however, cannot be seen on the condenser itself but rather on a nearby area running adjacent to A/C lines that are not leaking. Dye oftentimes nails the spot of the A/C leak, but other times it just tells the technician the general area in which to look. This specific A/C leak was spotted using a Cliplight Vector 7 UV light and dye (A/C Pro Pag 100 with UV dye). It was repaired using sealant (specifically U-View Leak Guard.)</p>

Using dye

The tried-and-true method to finding leaks is to use a UV dye and a broad spectrum UV light.

There is a good reason for this: It works almost all of the time.

The normal procedure for the technician is to use a UV light and scan the obvious trouble areas. This includes the evaporator, condenser, lines, compressor, expansion valve/office tube, Schraeder valves, and any associated seals.

A/C machine-safe sealants?

There are two kinds of technicians — those who use whatever A/C sealant they can find and hope it does not cause any issues and others who are really paranoid and use sealant detectors like the Neutronics Quick-Detect to find harmful sealants. If the technician wants to avoid potentially trashing their A/C machine, an in-line sealant filter such as the Charge Guard from Air Sept can be used to remove it.

The Society of Automotive Engineers has issued a standard (SAE J-2670) for sealants that can be used for mobile air conditioning that will pose no threat to standard air conditioning servicing equipment. U-View makes a sealant called “Leak Guard” that is oil-based, so it does not harden when it reacts with moisture like most other sealants. This particular product has a dye in it, so it can be used for the detection of very large leaks, as well as replacing the need to inject oil in the system because it is in of itself oil-based. In independent testing (by the author of the article) it has been found to work, even in a vehicle that has had the standard A/C sealant added to it to no avail.

Many shops make it a standard practice to inject oil, dye and then sealant in three different steps. Not only is this potentially risky to equipment, but it is time consuming.

New J-2670-certified products make it possible to mitigate the risk of A/C leaks, while at the same time lubricating the A/C system and putting in dye so larger leaks can be spotted.

Dye cannot always spot leaks for several reasons. Sometimes, it washes away or it is covered by road debris. In other instances, it is somewhere the technician cannot easily point an UV light at (i.e. behind the firewall where the evaporator is). Oftentimes, evaporators are sold without total confidence that they will fix the problem. Is there a way to be more certain about the location of an A/C leak?

Tags: A/C  Air conditioning 
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