Why Your HVAC Runs Constantly and How to Fix It
A system that never takes a break costs money and usually signals a fixable problem. In Vado, NM, long summer afternoons and chilly desert nights push equipment hard, but a healthy HVAC system should cycle off after it reaches the set temperature. If the blower or condenser runs nonstop, something is off in the load calculation, control sequence, or airflow. This article explains the common causes, how to diagnose them at home, and when to call an HVAC contractor in Vado, NM for targeted repair.
First, confirm what “running constantly” really means
Homeowners sometimes hear the indoor blower and assume the air conditioner or heat pump is also running. In reality, there are two different modes. The blower might run to circulate air with no heating or cooling, or the outdoor unit might be active, which uses far more energy. A quick look helps: if the thermostat fan setting is on “On,” the blower never stops by design. If it’s on “Auto” and you still hear air moving after the temperature is met, the control or a sensor may be wrong.
Most systems in Dona Ana County should complete a cooling cycle in roughly 10 to 20 minutes under normal load with proper sizing and ductwork. On a 102°F afternoon in Vado, a longer runtime is expected, but the system should eventually hit setpoint. If it cannot, it’s either undersized for the actual home, starved for air, low on capacity due to a fault, or chasing an inaccurate thermostat reading.
The usual suspects that keep systems running
Airflow restrictions lead the list. A clogged return filter, crushed flex duct in a crawl, or a closed supply register reduces the mass flow across the coil. The system then removes less heat per minute and runs longer. A simple filter check fixes many “always on” complaints. Filters in the Borderland tend to load faster in windy months, especially during dust events along NM-28 and fields near Vado Lake. Expect to replace a 1-inch filter every 30 to 60 days in summer; 4-inch media can run 3 to 6 months depending on dust and pets.
Refrigerant charge issues come next. Low charge from a small leak reduces capacity and can lead to coil icing. An iced coil restricts airflow, which further extends runtime. Homeowners sometimes notice poor airflow from registers and a sweaty suction line outside. If ice is present on the indoor coil or outdoor lines, shut the system off at the thermostat and switch the fan to “On” for 2 to 3 hours to melt ice, then call for service. Running frozen risks compressor damage.
Thermostat placement matters more than most people think. A thermostat mounted in direct sun through a west-facing window near Vado Elementary will read high in late afternoon and run the system continuously. The same happens if it sits above a supply register, near an attic hatch, or in a hallway with poor airflow. A relocation or a remote room sensor often fixes this without touching the equipment.
Duct leakage is widespread in older homes across the Mesilla Valley. Leaky supply ducts dump cooled or heated air into the attic or crawlspace, while return leaks suck in hot, dusty attic air. The system then fights a never-ending heat source and runs for hours. A quick pressure test and mastic sealing can reclaim 10 to 30 percent of lost capacity, which often shortens cycles and cuts bills.
Oversizing and undersizing both cause problems, but for different reasons. An undersized system never catches up during a 100°F spike and runs all day. An oversized system short-cycles, which is the opposite problem, but can still leave humidity high and comfort poor, tempting a homeowner to keep lowering the setpoint, which makes it feel like the system is running constantly. Proper Manual J and Manual S calculations solve this, but in the short term, airflow tuning and staging strategies can soften the issue.
Dirty coils slow heat transfer. Cottonwood fuzz, desert dust, and dryer lint on outdoor fins act like a blanket. Indoors, a dirty evaporator coil behaves like a clogged filter. Both force long runtimes. An annual coil cleaning keeps the system efficient, especially in Vado, where winds carry fine silt.
Aging equipment loses capacity over time. A 15-year-old condenser might test furnace repair Vado “within range,” but its real-world sensible capacity on a 100°F day can be notably lower than its nameplate. Expect longer cycles as parts wear. A capacitor on the edge, a weak blower motor, or a contactor with pitted points can all add small inefficiencies that add up to hours of extra runtime each week.
Finally, building factors matter. Single-pane windows on a west wall, leaky exterior doors, missing attic insulation, and poor shading add load. If the envelope gains more heat than the system can reject, it runs and runs. Improving the shell often shortens cycles without touching the equipment.
A quick homeowner diagnostic path
Before calling an HVAC contractor in Vado, NM, a focused, safe check can save time and money.
- Check the thermostat. Confirm mode, setpoint, and fan setting “Auto.” Replace batteries. Shade the thermostat temporarily if it sits in sunlight and see if cycles return to normal.
- Inspect the filter. If it looks gray or fuzzy, replace it. Note the size and MERV. If airflow improves and the system starts cycling off, the filter was the culprit.
- Look at the outdoor unit. Clear debris within a 2-foot radius. Gently hose the coil from the inside out if dust is visible. Avoid bent fins and high-pressure settings.
- Open supply registers and return grilles. Closed registers can raise static pressure and extend runtime. Balanced airflow beats closing rooms down.
- Observe the refrigerant lines. If frost or heavy condensation is present, shut cooling off and run the fan to thaw, then call for service for a likely refrigerant or airflow issue.
This simple sequence fixes a surprising share of constant-run complaints and gives clear information to share with a technician if the issue persists.
What normal cycling looks like in Vado’s climate
Cooling cycles lengthen as outdoor temperatures climb. With a correctly sized system, a 75°F setpoint, and decent envelope, expect cycles of 12 to 20 minutes when it is 92°F outside, with 2 to 4 cycles per hour. At 100 to 105°F, cycles may stretch to 25 to 40 minutes. If the system runs flat out for hours without reaching setpoint, even after sundown, there is likely a capacity, airflow, or control issue.
In winter, heat pumps in the Lower Rio Grande Valley may run longer, especially on nights that dip into the 20s. Defrost cycles can add noise and longer run times. Proper staging and balance keep it reasonable. Gas furnaces should follow shorter, steadier cycles if ductwork and filtration are correct.
Common fixes an HVAC contractor provides
After a site visit, a local technician will measure static pressure, temperature split, superheat, and subcooling, then inspect the duct system and controls. That data leads to practical fixes:
- Correct airflow. Adjust blower speed taps, replace restrictive filters with the right MERV and thickness, fix crushed flex, and seal key duct leaks. Small airflow gains often shorten cycles dramatically.
- Repair refrigerant issues. Locate and repair leaks, weigh in the correct charge, and validate superheat/subcooling. A proper charge restores capacity so the system can cycle off.
- Clean coils, blower wheel, and drain. Restored heat transfer and improved evaporator airflow bring cycle times back to normal and improve comfort.
- Reposition or replace the thermostat. Smart thermostats with remote sensors read the actual occupied space better. Proper location removes constant-run commands caused by bad readings.
- Address load problems. Simple attic insulation top-offs, weatherstripping, and window film on west exposures reduce run time. Technicians in Vado routinely see 10 to 15 percent runtime reductions after basic envelope tune-ups.
A good contractor will also weigh the age and cost curve. If the condenser is 14 to 18 years old, a repair may be a bridge, but a right-sized, high-SEER2 replacement can reduce runtime and bills for the next decade.
Real examples from the Mesilla Valley
A 1,700-square-foot home off Vado Drive with a 3-ton split system ran continuously from 2 p.m. until 8 p.m. on 101°F days. Static pressure measured high at 0.95 in. w.c. due to a 1-inch MERV 13 filter in a grille sized for MERV 8. Swapping to a 4-inch media cabinet and opening three supply registers dropped static to 0.58, raised airflow by roughly 200 CFM, and reduced late-day cooling runtime by about 30 minutes per hour.
Another case near NM-189 had a hallway thermostat directly across from a west-facing door. Afternoon sun heated the wall. The thermostat read 78 while the living room was 72. The system ran and ran, and the owners kept lowering the setpoint. Moving the thermostat inside the living area and adding a shade over the door fixed the issue in one visit.
A farm home south of Mesquite had return leaks in the attic. The return pulled 110°F dusty air; the coil iced over every afternoon. Sealing returns with mastic, adding a dedicated filter rack, and cleaning the evaporator stopped the icing and restored normal cycling.
How to prevent constant runtime through the season
Routine maintenance is the cheapest insurance. In a dusty, windy area like Vado, spring coil cleaning, a static pressure check, and a filter strategy matched to the grill size go a long way. Many homes benefit from a media cabinet that accepts 4-inch filters. It lowers static, improves IAQ, and allows longer service intervals.
Thermostat calibration and placement should be reviewed during a maintenance visit. A technician can confirm that what the thermostat reads matches the actual room temperature within 1°F. If it does not, a relocation or wireless remote sensor is worth it.
Duct sealing pays back quickly when ducts run through attics. Crews can test leakage and target the worst joints, boots, and plenums. It is messy work but once done, the system runs less, dust drops, and rooms balance.
On the envelope side, shade west windows, add attic insulation to at least R-38 if it is lower, and seal doors. These steps reduce the cooling load and bring runtime down in the hottest stretch of July and August.
When the compressor is fine but the blower never stops
Sometimes the outdoor unit cycles normally, but the indoor blower keeps running. A few causes stand out:
- Thermostat fan set to “On.” Switch to “Auto.”
- Stuck fan relay or a failed control board on furnaces and air handlers. The fan output stays energized. A board replacement fixes it.
- High-limit or freeze protection issues. If a limit trips, the control may command the blower to cool the heat exchanger, leading to extended runs. That points to airflow problems or a dirty coil.
- Humidification or IAQ accessories wired to run the fan continuously. In homes with certain air cleaners, the fan is set to circulate 24/7. That is a choice, not a failure, but it adds cost.
A technician can test the G and Y circuits at the board to confirm whether the call for fan is from the thermostat or a stuck relay.
Heat pump quirks that look like constant running
Heat pumps often run longer than gas furnaces in winter. That is normal. In a cold snap, auxiliary heat may kick in. If the unit never cycles off and the bill jumps, a stuck balance point or failed outdoor sensor can leave heat strips on too long. Defrost cycles add noise and steam outside, which is normal. What is not normal is a never-ending defrost or frequent short defrosts. That hints at control or sensor problems.
Technicians can confirm defrost logic, sensor values, and staging. A small sensor replacement can restore correct cycling and lower bills.
How long fixes take and what they cost
Time and cost depend on the root cause:
- Filter, coil rinsing, and thermostat settings adjustments often resolve the issue within an hour.
- Refrigerant repairs vary. Finding and fixing a small leak in a flare or service valve might take 1 to 3 hours; coil leaks take longer and may lead to coil replacement.
- Duct sealing in a typical Vado attic can be a half-day to full-day job, depending on access and leak size.
- Control board or relay replacements are usually same-day repairs if parts are local.
A reputable HVAC contractor in Vado, NM will offer an on-site diagnosis with transparent pricing before work begins. Ask for readings: static pressure, temperature split, superheat, and subcooling. Numbers show whether the fix restored capacity.
What to try before scheduling service, and when to stop
It is reasonable for a homeowner to handle filters, outdoor coil rinsing, thermostat checks, and looking for blocked registers. It is risky to open refrigerant circuits, pull blower assemblies, or wash indoor coils without training. If ice forms, if breakers trip, or if the outdoor fan runs without cooling the home, turn the system off and call.
If the unit is old and repairs stack up, consider a replacement quote. Many Vado homes were originally fitted with equipment sized to the old envelope. After window upgrades and insulation, a smaller, two-stage system often runs steadier and uses less energy, with normal, shorter cycles even on hot days.
Local context that matters in Vado
High dust, cottonwood pollen, and occasional haboob conditions punish filters and coils. Homes near fields pick up more airborne load. Wind-driven infiltration through attic hatches or can lights adds heat gain. Electrical service can see voltage dips that stress capacitors. These local realities show up as long runtimes and nuisance failures.
A local technician who works the I-10 corridor understands these patterns. Filter plans change with spring winds. Coil cleanings are scheduled before the June heat. Duct sealing focuses on return leaks common in older ranch homes. This practical, local approach reduces runtime and extends equipment life.
Ready for expert help
If the system runs nonstop, comfort drops, or the bill spiked, it is time for a thorough check. Air Control Services serves homeowners across Vado, La Mesa, Berino, and the Mesilla Valley with diagnostic visits that focus on airflow, charge, and controls, not guesswork. The team measures, explains the findings in clear terms, and fixes the exact cause so the system cycles normally again.
Call to schedule a diagnosis or book online for a convenient time. Whether it is a clogged filter, a thermostat heat source, a leaky return, or a refrigerant issue, an experienced HVAC contractor in Vado, NM can restore proper cycling and lower your energy costs fast.
Air Control Services is your trusted HVAC contractor in Las Cruces, NM. Since 2010, we’ve provided reliable heating and cooling services for homes and businesses across Las Cruces and nearby communities. Our certified technicians specialize in HVAC repair, heat pump service, and new system installation. Whether it’s restoring comfort after a breakdown or improving efficiency with a new setup, we take pride in quality workmanship and dependable customer care.
1945 Cruse Ave Phone: (575) 567-2608 Website:
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88005
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