Gas furnaces need one annual service visit before winter. Heat pumps need two — one before cooling season in spring and one before heating season in fall. The reason is simple: a heat pump runs year-round in both modes, so both seasons represent real stress on the system. Skipping the spring visit is how people end up calling for emergency AC service in August.
This post covers what you can realistically do yourself and what requires a licensed technician. I have seen homeowners take on work that damaged equipment they were trying to maintain. I have also seen homeowners who did not know they could do anything themselves and called for issues that cost them nothing to fix. This is meant to give you an accurate picture of both.
What You Can Do Yourself
Filter Replacement
For central systems with standard flat filters, change them every one to three months. How often depends on whether you have pets, how dusty your home runs, and how much the system operates.
Most residential heat pumps work best with filters in the MERV 8 to 11 range. Do not assume a higher MERV rating is always better. MERV 13 and above creates significantly more airflow resistance, and if your system was not designed to handle that restriction, you will get problems: the evaporator coil can freeze in cooling mode, the heat exchanger can overheat, and blower motors can burn out working against the pressure. If you want better filtration, use a thicker filter (a 4-inch MERV 11 creates less restriction than a 1-inch MERV 11) rather than jumping to a higher rating on the same size filter.
For ductless mini-splits, the filters are washable. Check them every two to four weeks and clean as needed. The process: turn the unit off, open the front panel, pull out the filters, rinse them with water and a small amount of mild dish soap, and let them air dry completely on a counter before reinstalling. Do not reinstall a wet filter.
Outdoor Unit Clearance
Walk around your outdoor unit and check that nothing is encroaching on it. The minimum clearance is roughly two to three feet on all sides and three to four feet above. Shrubs, stored equipment, stacked wood, and garden beds creep in over time.
Clear away leaves, pine needles, grass clippings, and any debris that has accumulated against the coil. This matters more in Western Washington than in most places because of the amount of material that comes off trees and because wet debris stays wet and packs down against the fins.
One thing I see homeowners do that causes damage: pressure washing the outdoor coil. The aluminum fins are delicate enough that a pressure washer will bend and crush them. Bent fins restrict airflow and cannot easily be straightened. If the coil needs rinsing, use a regular garden hose at normal pressure, and spray from the inside outward, not from outside in. But for most homeowners, clearing the debris with your hands or a soft brush is enough.
Vents and Registers
Make sure supply and return vents throughout the house are not blocked by furniture, rugs, or curtains. This one sounds obvious but is easy to overlook after rearranging a room.
Do not close vents in unused rooms to “save energy.” I understand the logic, but it does not work that way. Your system moves the same volume of air regardless of how many vents are open. Closing vents backs up static pressure in the ductwork, which can freeze the evaporator coil in cooling mode, overheat the heat exchanger in heating mode, and shorten the life of the blower motor. The energy savings are not real, and the potential damage is.
Condensate Drain Inspection
The condensate drain carries water away from the indoor unit as it pulls humidity from the air. Over time, algae and sludge build up in the drain pan and line.
You can inspect this yourself. On a mini-split, look at the small drain line where it exits the indoor unit and check the drain pan for visible slime, algae, or standing water. For central systems with accessible drain pans, take a look when you change the filter.
Pan treatment tablets (commonly sold under names like HVAC Guys Flow Tabs or QwikTreat) dissolve slowly in the pan and prevent algae buildup. They are inexpensive, non-toxic, and completely safe to use. Drop one in every month or two during cooling season. A clogged condensate drain can cause water damage to walls and ceilings, or trigger your system’s automatic shutoff, which will look like a system failure when it is just a backed-up drain.
Line Set Insulation
For mini-splits and split-system heat pumps, take a few minutes once a year to walk the refrigerant line set from the outdoor unit to where it enters the building. Look for:
- Sections where the foam insulation is missing, cracked, or deteriorated
- Oily residue on or around the lines, which indicates a refrigerant leak
- Ice forming on the lines
Missing insulation alone causes efficiency loss. The other two items indicate problems that need a technician. Call if you see them.
Thermostat Check
Verify your thermostat responds correctly: set it to heat, confirm the system runs and produces warm air, then switch to cool and do the same. Check the battery if it is battery-powered. Look for any error codes on the display. This is particularly worth doing in spring (before you need cooling) and in fall (before you need heat), rather than finding out the system will not switch modes during the first cold snap in October.
What Requires a Technician
Refrigerant Check
Homeowners cannot legally handle refrigerants. EPA Section 608 of the Clean Air Act requires certification to purchase, handle, or service refrigerant-containing equipment. This is not just a recommendation; it is federal law.
What you can watch for that signals low refrigerant or a leak: the system runs longer than usual but struggles to reach the setpoint, energy bills spike without an obvious cause, you hear a hissing sound from the outdoor unit, or you see frost or ice on the outdoor unit at times that are not part of the normal defrost cycle. If you notice any of these, call a technician.
Coil Cleaning
The evaporator coil (inside) and condenser coil (outside) both accumulate dirt over time, which reduces heat transfer and system efficiency. Both require professional cleaning.
The evaporator coil is enclosed inside the air handler and is delicate. The condenser coil has those thin aluminum fins that bend under pressure. I have seen homeowners try to clean condenser coils with pressure washers and end up with coils that needed to be replaced. A trained technician uses appropriate coil cleaner and low-pressure rinse technique. Leave this one to us.
Electrical Connections
Inside the outdoor unit and the air handler, electrical connections loosen over time from vibration. Loose connections arc, overheat, and can cause component failures or fires. Checking and tightening them requires turning off power at the disconnect and working around high-voltage components. This is professional work.
Capacitor and Contactor
The capacitor is a cylindrical component in the outdoor unit that gives the compressor and fan motors the electrical jolt they need to start. The contactor is essentially a relay that delivers power to the major components when the thermostat calls.
Both need periodic inspection and both have signs of failure homeowners can watch for: if the system will not start, makes a buzzing sound without the compressor running, or the fan runs but the compressor does not engage, these components are often the cause. They are not expensive repairs.
The reason homeowners should not inspect or replace them: capacitors store electrical charge even when power is completely off, and contact with a charged capacitor can cause serious injury. Testing a capacitor correctly requires a multimeter and knowledge of what the readings mean. If you suspect capacitor or contactor failure, call a technician. It is one of the more straightforward HVAC repairs, and there is no reason to take the risk yourself.
System Performance Measurement
A technician at a service visit will measure the temperature difference across your system’s coil, called the delta T or temperature split. In cooling mode, the air returning through the coil should be 16 to 22 degrees warmer when it leaves. In heating mode, the split is typically 20 to 30 degrees. Numbers outside these ranges indicate airflow problems, refrigerant charge issues, or dirty coils. They also check refrigerant superheat and subcooling, which require manifold gauges and training to interpret correctly.
Heat Pump Specifics
The Defrost Cycle
If you have a heat pump and have not seen it go into defrost mode, you will at some point. During cold, humid weather, frost accumulates on the outdoor coil as the system pulls heat from outside air. When this happens, the system temporarily reverses and runs in cooling mode to push hot refrigerant through the outdoor coil and melt the frost.
What this looks like: the outdoor fan may stop, steam rises from the outdoor unit, and warm air from the house is briefly redirected. The cycle typically lasts five to fifteen minutes. This is normal and nothing is wrong.
When to call: if the system is going into defrost multiple times per hour or staying in defrost much longer than fifteen minutes, that warrants a technician visit. Excessive defrost cycles can indicate a dirty outdoor coil restricting airflow, a refrigerant problem, or a defrost control malfunction.
The Reversing Valve
The reversing valve is what allows a heat pump to switch between heating and cooling. It redirects refrigerant flow depending on the mode.
Signs of reversing valve problems: the system blows warm air when set to cool, blows cold air when set to heat, or will not switch modes at all. You may also hear unusual clicking or hissing when the thermostat changes from heating to cooling. Reversing valve failure requires professional diagnosis and repair.
When to Schedule Service in the Pacific Northwest
Spring (March through May): Before cooling season and before technicians get booked solid. PNW outdoor coils frequently develop algae and moss from wet winters, and the coil cleaning done at a spring visit addresses this directly.
Fall (September through October): Before the heating season starts. Our heating season runs from roughly October through April. Discovering a problem in November means months of degraded comfort or emergency repairs during the period of highest demand.
If you have not had your system serviced in more than a year, or you have moved into a home and do not know the service history, schedule a visit. The cost of a tune-up is a fraction of the cost of a repair that a tune-up would have caught.
If you are in Kelso, Longview, or the surrounding area and want to schedule a spring or fall service visit, give me a call. I will tell you honestly what I find.