With the advent of printed circuit boards and LED lights, the fine art of HVAC equipment troubleshooting is starting to go by the wayside. On many service calls we go to the equipment, read the code it flashes, repair what it says it wrong, and hope for the best. That's too bad, because good troubleshooting is what sets the professional technician apart from the parts changer.
In an economy like the one we're currently experiencing, lots of older (and less technically advanced) equipment is being repaired instead of replaced. Homeowners simply don't have the finances to install new equipment. This is where the skilled troubleshooter is invaluable. We are the “bailout” to our homeowners.
Technicians must repair systems in a timely and effective manner. Yet, too often we get stuck in a rut of knocking on the door, setting the stat, finding the obvious problem, repairing it, collecting the bill, and rushing to the next call.
Effective troubleshooting calls upon our ability to look at every aspect of the unit, including duct work, grille placements, and the high- and low-voltage wiring. The wiring must be safe and up to local codes, and able to do the job the owner needs it to do, in the most energy-efficient manner.
Start With the Homeowners
Like a skilled surgeon wielding a scalpel, you have to dissect the system. But first, it's always a good idea to get as much information from the homeowner as you can. There are a few key questions to ask: Did this problem just start, or has it been going on for a while? Did the system malfunction after they did something, such as mowed the grass, made home improvements, or had other repairs made to their home? For intermittent issues, find out if there's any consistency to it, such as a certain time of day.
Ask if the homeowner has attempted a repair on the HVAC system. We live in a do-it-yourself (DIY) world now, and with the coming of age of the Internet, there's just enough information out there for homeowners to quickly get in over their heads.
Ask about the maintenance schedule they're on. If the homeowner doesn't have a service agreement, you already know that the machine needs to be cleaned and serviced before diagnostics can begin. It also gives you the opportunity to sell a service agreement while you're there. Many contractors spend countless dollars on advertising and lead generation, yet technicians go into homes every day and leave money on the table by not informing customers of the services their companies offer.
The most important question to ask is the location of the air filter and the last time the filter was replaced or cleaned. Many homeowners don't change filters as often as needed; some are even unaware the machine has a filter in it.
Time to Troubleshoot
After gaining as much information from the homeowner as you can, it's time to begin troubleshooting. First, familiarize yourself with the wiring diagram, all of the components, controls and safeties. After you've done this, the real work begins. With your trusty volt meter in hand, start where the furnace connects to the power grid, (wall outlet, switch box, etc.). Thanks to your analysis of the wiring diagrams, you should know the value you're looking for. If the value matches what's stated, you can proceed; if not, determine why that value isn't there and repair that issue first, keeping in mind that there may be an underlying problem that caused the power failure.
The wiring diagram will show the route you need to take in making the repair. If the wiring diagram is missing, take a few minutes to sketch one out. Start by listing the major components; then list the minor components and wires that connect them. Leave your drawing with the system; it will be a time-saver for you or the technician who services it next time.
Begin by checking each component, comparing the values you have with the values listed on the component. Keep detailed notes of what you find, as these will be needed as you do your paperwork.
Most technicians stop too quickly. A problem is encountered and repaired, the machine is operating, and our minds begin to dwell on the 12 other “no heat” or “no cool” we have on the schedule for the day. But is the system really fixed, or is it just up and running for now? If there is another problem, there will be a callback. This will cost your company money, and cause a lack of confidence on the part of the customer. So we need to have a stick-to-it mentality and thoroughly diagnose and repair the system.
A Thorough ‘No Heat’ Check
For example, let's say you go on a service call for a gas furnace not heating. You find a bad fan motor capacitor, replace it, and restart the system. The problem you found was electrical, the system is heating and the homeowner is happy, so it's time to move on, right? Wrong! Dig a little deeper. Customers are going to be billed a diagnostic fee, so give them their money's worth.
Check the gas pressures, both inlet and manifold. Use your combustion analyzer to make sure the machine is burning clean and efficiently. Make any adjustments that are necessary to make the furnace operate at its designed and maximum efficiency. With ever-increasing energy costs, it's part of your job to ensure that customers aren't spending any more money than they must to heat and cool their homes.
A Thorough ‘No Cool’ Check
Six months later it's summertime. You go on a no-cooling call and find a bad contactor. You replace it and restart the system. Cool air is flowing and the homeowner has his checkbook in hand. However, you still have a little more work to do.
First, let the system run for a few minutes (15 by most manufacturer's recommendations) and check the refrigerant level. Most of us are guilty of cranking the machine up, slapping our gauges on, grabbing the suction line and adding refrigerant till the line is good and cold. The increase of the minimum SEER ratings and the use of the TXV has made the “beer can-cold” method for charging obsolete.
Fifteen minutes of run-time ensures that there is a full column of liquid at the TXV inlet and the system is stabilized and ready for accurate superheat and sub-cooling temperatures to be taken. Most manufacturers place a chart on the machine giving the value you need to look for. You can also take amp-draw readings on the vital components, give the system a thorough examination, and discuss with the homeowner any other services that your company may provide.
Wrapping Up the Call
Note on the invoice the operating conditions, temperatures, pressures, electrical values, and any items on the equipment that are operable but that may be nearing the end of their useful life. Include conditions of heat exchangers and coils. This gives the homeowner the information that justifies the billed amount. Your notes will also give the homeowner the information he or she needs to help make the decision about a replacement product. Arrangements can be made towards saving up for or securing financing for a replacement product in the near future. Of course, if there's a life, health, or property damage threat posed by the equipment, it must be taken offline until proper repairs can be made.
Troubleshooting steps can and should be used on equipment with printed circuit boards as well as the equipment's self-diagnostics. Although the boards themselves are not user serviceable, you'll still want to verify that they're diagnosing correctly.
The Technician's Responsibility
Proper troubleshooting skills increase customer confidence and make our companies more profitable. We can reduce costly callbacks and help keep equipment and parts costs lower. Many compressors and circuit boards returned under warranty are either not faulty or were damaged by another defect in the system that wasn't found, and repaired on an initial service call. Even though we're not billed for the warranty parts, they're not free: manufacturers figure the cost of maintaining in-force warranties into the price of parts and equipment. Reducing the number of warranty claims keeps our costs in check.
Technicians have a responsibility to customers, employers, and ourselves to ensure that we're well-informed and properly trained. Attend as many classes and seminars as you can. Equipment and technology change everyday, and technicians must stay informed.
And, I can't overemphasize the importance of North American Technician Excellence (NATE) certification in helping technicians reach the top.
Wherever technology takes us, we must keep our troubleshooting skills sharp. Those skills go a long way toward making us the best technicians this field has to offer.
Gary Hodges is the service manager at Carthage Heating & Cooling, Carthage, MS. He won the 2008 North American Technician Excellence (NATE) Certified Technician Competition, held at HVAC Comfortech 2008 in Atlanta. Hodges can be reached at 601/267-4611, or by e-mail at email@example.com.