Air conditioning system issues

Feb. 13, 2018
How preventative maintenance on HVAC systems can help to stave off bigger problems down the road.

Vehicles affected – 2011 Cadillac SRX, all vehicles with Automatic Temperature Controls

Issue – Lack of A/C system maintenance causing poor HVAC performance

Tools used:

·        Vehicle information

·         Refrigerant identifier

·         RRR machine

·         Electronic leak detector

·         Bi-directional scan tool

·         Thermometer

·         DMM with thermocouple

·         Thermal imaging camera

This Tool Briefing article is going to take a slightly different approach; specifically, it will look at how performing maintenance can prevent issues. We all know that performing preventative maintenance will help avert larger issues on many vehicle systems, such as the engine, transmission and brakes, but there are other systems on a modern vehicle that also need maintenance. One of the most neglected systems is HVAC (heating, ventilation, air conditioning).

Many shops neglect to think about how they may be able to prevent failures in a HVAC system by performing an annual maintenance service. Most shops are able to repair a system properly after a failure, but there are many cases where performing an inspection would have been able to prevent the failure from occurring in the first place.  

You might consider whether your shop serves your clients better by repairing their vehicles to fix issues, or by maintaining them in an effort to prevent problems – or both. You may think it is more profitable to repair the vehicle rather than maintain it, but in reality, preventative maintenance and repairing issues found during those services can be very profitable, too.

Step 1 – Obtain information

The beginning of the air conditioning season is a perfect time to perform maintenance. In fact, once a system is used after cold months of not using the A/C, many problems can develop.

Start by asking your customer questions such as:

·         Are you having any issues with your HVAC system now?

o   Many times, the system may not be defogging properly, or not getting warm enough, indicating an issue

·         Did you experience any issues last fall?

o   Not cooling enough, or not cooling side-to-side properly can be indicators of a pending problem

·         Are there any strange noises coming from the dash?

o   This may indicate blend door or fan motor issues

·         Do you notice unpleasant odors inside the vehicle with the fan running?

o   This could indicate a mold issue

Once you have this information, you should research your digital information source. Obtaining TSB’s, or in some cases, any open recall notices may show potential issues.

We checked Identifix Direct Hit and found an open recall on our 2011 Cadillac SRX for an updated reprogram for the Electronic Climate Control (ECC).  The recall called for reprogramming the ECC to repair an intermittent issue where the system is unable to control the defrost system.

Next, you’ll want to perform an Air Conditioning Performance Test. Each manufacturer, and in some cases, different vehicles from the same manufacturer, have very specific steps that must be done to determine if the A/C system is performing correctly under the current ambient temperature conditions. As temperature or humidity changes, system pressures and outlet temperatures change. Performing the manufacturer’s specific test allows the technician to determine if the system is functioning correctly at the current outside temperature and humidity.

Step 2 – Perform System Tests

Perform the System Performance Test exactly as it is detailed in the specs for the vehicle. In order to do this test, you will need to connect your RRR machine. Before connecting your machine, you should connect a refrigerant identifier to make sure there are no contaminants in the system, which may cause the A/C system to not operate correctly, and could possibly damage your RRR machine.

It is necessary to record the ambient air temperature and relative humidity for the performance test. Some RRR machines have this capability, but if yours does not, a temperature gauge placed a few feet in front of the radiator, or even readings from your scan tool, can be used.

Connect your RRR machine and record the high- and low-pressure readings, as well as the left vent outlet temperatures, as indicated in the performance test. The readings from the test will be compared to the chart (see image) and used to determine if the system is performing correctly.

In most cases, pressures lower than expected indicate the system is low on refrigerant. Low refrigerant causes two things: poor system performance, and, since refrigerant oil is carried through the system to lubricate components, eventual system failure due to lack of lubrication. With today’s A/C systems using extremely small amounts of refrigerant, less than 16 oz in many cars, even small leaks can cause big issues, both in performance and loss of lubrication.

Even if you have determined there is a system leak, it is still necessary to do some additional system tests. Since many HVAC systems use automatic temperature control, a complete scan of both the Body Control Module, and the HVAC module is necessary. If any codes are present, you will want to perform diagnostic tests to determine the cause of the code. Scan tools in fact contain software calibration part numbers for each system module. This information may be relevant to verify that the latest software version is present or should be changed to correct any known issues.

If you note performance issues and the system is full, a contact thermometer or DMM with a thermocouple is an extremely valuable testing tool to help determine the cause. Certain tests can help to compare inlet and outlet temperatures of the evaporator and condenser to determine the most likely causes of issues. Since this is a short article and temperature tests can vary, check your vehicle information source for specifications and the specific test procedure for the vehicle you are testing.

Step 3 – Repair the Vehicle

Our Cadillac had a recall for reprograming the A/C controller. To address this we looked up the current calibration part number in the A/C module with our Launch Tech Pad II scan tool, then compared it to the one listed for the VIN number. We found the recall was still open and needed to be corrected.

For GM vehicles, it is relatively easy to determine if any of the modules have the most current calibration. Start by recording the VIN number. Go online to the link and enter the VIN. Once the VIN is entered, select “Get Cal ID.” Then select the module you are obtaining information on, in this case, the Remote Heater and Air Conditioner Module. Click on “Next,” then click on “Programming and “Next” again. The correct part number for the module will appear. Note this part number and compare it to the module part number obtained with your scan tool. If they are different, some active or potential issues may be corrected by updating the software. If it is a recall, like this Cadillac, advise your customer that it should be repaired and will most likely be done by the dealer at no charge. We informed the customer and they decided to have us finish the maintenance on the system while they returned to the dealer for the module reprogram.

If the system is low on the refrigerant charge, look for visible leaks or use your electronic detector to locate them. After you find and correct any leaks, charge the system completely and make sure the correct amount of oil is in the system. Remember – if you decide to add dye to highlight any other leaks, be sure to reduce the amount of oil in the system by the same amount of dye you put in.

Additional testing can be done using a Snap-on Tools thermal imaging camera to determine if seat heaters/coolers are functioning properly and to look for obstructions in vents. Inconsistent temperatures between the left and right sides of the vehicle may indicate either an improper charge, or vent or door issues preventing even flow. Uneven temperatures in window heat strips or seat heaters may indicate broken elements.

Any A/C job should not be considered complete until a few housekeeping duties are done.

·         Remove any leaves or debris from the fresh air intake below the windshield and replace the cabin air filter

·         Clean any debris from in front of the condenser and between the condenser and radiator

·         Inspect and replace any damaged or missing seals between the radiator and condenser

·         Inspect and replace any damaged air dams that direct air to the radiator and condenser

·         Inspect and test the condenser cooling fan for both low and high-speed operation

·         Make sure the blower fan is working at all speeds

Step 3 – Calibrate and Test the System

Once the system has been fully charged and the cleaning of the condenser and vent system has been done, it is time to evaluate if the system is fully functioning. Start with connecting your scan tool and recalibrating all of the door actuators. There will be specific instructions for performing this test for each type of vehicle, but generally speaking, this is done bi-directionally through selecting the function in a “Special Test” in the HVAC module.

Once this is done, complete another System Performance Test. If the system is functioning correctly, the test results you achieve will match with a normally operating system.

With the New Year came some new regulations for the distribution and purchase of refrigerants. Please check to make sure you are complying with these regulations and, most importantly, remember that every automotive technician that services, tests or repairs A/C systems on mobile vehicles must have an EPA 609 certification. The fines for not complying can be devastating.

To sum things up, there are plenty of opportunities to perform system maintenance on your customer’s HVAC systems and catch small problems before they become big ones. If you can do so, you will be generating a lot of goodwill for your business.

About the Author

Barry Hoyland

Barry Hoyland has been in the independent aftermarket for more than 45 years as a technician, technician instructor, shop owner, and shop management consultant. He owned and operated a successful Southern California automotive repair center that offers complete auto care and specialized in emission and diagnostic services for over 28 years. Hoyland also owned a company that modified vehicles to perform as emergency response units and mobile command centers, incorporating high-end electronic components into today’s vehicles. Hoyland has experience with all size and types of vehicles including traditional gas, hybrid electric, alternative fuel, and heavy duty diesel trucks.

Hoyland has provided consulting services for many automotive shops, fleets, and government agencies in order to improve their operational efficiencies.

In addition, he has worked with many NHRA drag racing teams as a crew chief on supercharged alcohol and nitro-methane fueled cars and currently serves as a crew chief on a Top Alcohol Funny Car, a Nostalgia Funny Car, and a Nostalgia Alcohol Dragster

Hoyland holds certifications in ASE: A1, A6, A8, and L1, MACS 609, maintains a California Advanced Emission license, and a CDL with endorsements for double and triple trailers, tankers, and HazMat.

When he is not helping to run a shop in the Pacific Northwest, Hoyland travels across the U.S. as an instructor of technical and shop management courses, many of which he has developed. 

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