top of page

AC Not Cooling? Furnace or Heat Pump Not Heating? Try These Steps First.

Most "no cool" and "no heat" calls come down to a thermostat setting, a tripped breaker, or a clogged filter.
Find your system below and walk thru the checklist before you pay for a service call.
Still stuck? Cogburn's offers same-day service across Denton County.

✓ Family-owned since 1999   ✓ Same-day service   ✓ Upfront pricing   ✓ Denton County local  

(Click the System That's Not Working)

❄️ AC Not Cooling

🔥 Furnace Not Heating

♻️ Heat Pump Not Heating

Not sure which you have? If your outdoor unit runs in the winter to make heat, you have a heat pump. If it only runs in summer and you have a gas line to the indoor unit, you have a furnace.         Still unsure? Call (940) 229-6243

⚠️ Stop — Call Us Immediately If You Notice Any of These

Do not troubleshoot. Turn the system off at the thermostat and call 940-229-6243.

  • You smell gas (rotten egg odor) — leave the house, call Atmos Energy first, then us

  • Smoke, sparks, or scorch marks on the unit, wiring, or vents

  • Loud grinding, banging, or electrical buzzing

  • Water actively leaking onto electrical parts or through a ceiling

  • The breaker trips again after you reset it once

  • Signs of carbon monoxide exposure (headache, dizziness, nausea) — leave and call 911

Refrigerant, gas, and electrical work are pro-only for exactly these reasons.

AC Not Cooling? Try These 5 Checks — About 5 Minutes

1. Check the thermostat

  1. Set mode to COOL (not OFF, HEAT, or FAN only)

  2. Set the target temp at least 5°F below current room temperature

  3. Blank display? Replace the batteries or reseat the thermostat on its wall plate

  4. Confirm a schedule or "hold" isn't locking in a higher setpoint

2. Check the air filter

  1. A clogged filter is the most common cause of weak airflow and frozen coils

  2. Gray, matted, or can't see light through it? Replace it

  3. North Texas summers: change 1" filters every 30–60 days

🧰 Order the Right Filter for Your System

3. Check the breakers

  1. Open the electrical panel; look for "AC," "Air Handler," "Furnace," or "Condenser"

  2. A tripped breaker sits between ON and OFF — push fully OFF, then back ON

  3. Trips again immediately? Stop. That's an electrical fault. Call us.

4. Look and listen at the outdoor unit

  1. Is the outdoor condenser running? You should hear the fan and see it spinning from the top

  2. Clear leaves, grass clippings, and cottonwood fluff off the coil fins

  3. Keep at least 2 feet of clearance on all sides. 12 to 14" on the house side.

  4. Humming but the fan isn't spinning? Shut it off at the gray disconnect box on the wall and call us

5. Walk through the house

  1. All supply vents open and unblocked by furniture, rugs, or curtains?

  2. All return-air grilles clear?

  3. Ice on the copper lines or coil? Turn the system OFF, set the thermostat fan to ON for 1–2 hours to thaw. If it re-freezes, call us.

Worked through all five and still no cool air?

​📞 (940) 229-6243

Gas Furnace Not Heating? Start Here

This section is for gas furnaces. If your outdoor unit runs in winter to produce heat, skip to the Heat Pump section instead.

1. Thermostat

  1. Set to HEAT, target temp 5°F above room temperature. Replace batteries if the display is dim or blank.

2. Power to the furnace

  1. Most furnaces have a switch that looks like a light switch on or near the unit — make sure it's ON. Then check the breaker labeled "Furnace" or "Air Handler."

3. Gas supply

  1. Confirm the gas shut-off valve on the pipe to the furnace is parallel with the pipe (open). If your water heater or stove are also out, call Atmos Energy — the issue is upstream.

4. Air filter

  1. A clogged filter makes a furnace overheat and shut down on a safety limit. Same rule as above.

🧰 Order the Right Filter for Your System

5. Condensate drain (90%+ efficiency furnaces)

  1. A clogged condensate line trips a float switch and stops the unit. Look for standing water in the drain pan.

​📞 (940) 229-6243

Heat Pump Not Heating? Start Here

Heat pumps behave differently from gas furnaces, and two of the most common "problems" are actually normal operation. Read the first two items before you call.

First: cool-feeling air is often normal

  1. A heat pump delivers supply air at roughly 85–110°F. A gas furnace delivers 125–150°F. Since your skin sits around 90°F, properly working heat pump air can feel cool on your hand even while it's heating the house correctly

How to check it properly: put a meat or cooking thermometer in a supply vent for 5 minutes. Above 85°F means the system is working. Also confirm the house is actually holding its setpoint over a few hours.

Second: frost on the outdoor unit is often normal

Light white frost on the outdoor coil in winter is normal physics, not a breakdown. Your heat pump runs a defrost cycle every 30–90 minutes that melts it off in 2–10 minutes. During defrost you may hear a whoosh, see steam rising off the unit, and feel briefly cool air indoors — all normal

Call us if instead you see: solid ice encasing the coil or fan blades, ice filling the top grille, ice that doesn't clear after 4+ hours above freezing, or a unit frozen into a block

1. Check the thermostat

  1. Set to HEAT (not AUTO, not COOL), setpoint a few degrees above room temp

  2. Set the fan to AUTO, not ON. A fan stuck on ON blows unheated air between cycles and feels like a failure (TruComfort)

  3. Check that Emergency Heat or Em Heat is NOT switched on (see below)

2. Is Emergency Heat accidentally on?

Emergency heat is a manual mode that shuts your heat pump off and runs electric resistance strips only. It heats the house but can cost 2–3× more per day, and many homeowners leave it on by mistake after a cold snap

  • Use Em Heat only when the outdoor unit has failed and you're waiting on service

  • Auxiliary heat ("Aux Heat") is different — it kicks in automatically below roughly 40°F to supplement the heat pump. Seeing "Aux Heat" on your thermostat during a North Texas cold snap is normal (Trane)

  • If Aux Heat stays on constantly in mild 50°F+ weather, that's worth a service call

3. Check the air filter

A clogged filter chokes airflow and is a leading cause of weak heat and coil freeze-ups. Replace it, then let the system run 30 minutes before judging

🧰 Order the Right Filter for Your System

4. Check BOTH breakers

Heat pumps typically have two breakers — one for the outdoor unit and one for the indoor air handler. If only the indoor breaker is on, the fan runs but no heat is produced.

  • Reset any tripped breaker fully OFF, then ON — once only

  • Trips again? Stop and call us

5. Confirm the outdoor unit is running

Unlike a furnace, your heat pump's outdoor unit must run in winter to make heat.

  • Go outside and confirm the fan is spinning and the unit is humming

  • Clear leaves, snow, and ice from around it; keep 2 feet of clearance on all sides

  • Never chip ice off the coil with a tool — you'll puncture the fins. Pour lukewarm (never hot) water over it instead

  • Outdoor unit dead silent while the thermostat calls for heat? That's a service call

Still no heat after these checks?
 

​📞 (940) 229-6243

Still Not Working? Pick Your Next Step

Schedule Service

Same-day diagnostic visits across Denton County. Upfront pricing before any work starts.

Buy the Right Filter

Get the exact filter size for your system, shipped to your door.

Shop Filters

Free Replacement Quote

System 12+ years old? Get a no-pressure quote on a new high-efficiency system.

Get My Quote

Why Denton Homeowners Call Cogburn's

​

  • Family-owned since 1999 — same local family, same phone number, 25+ years

  • Same-day service — most calls handled the day you call

  • Upfront pricing — you approve the price before we start

  • North Texas specialists — we size and service systems for our heat, our humidity, our dust

  • Diagnostic fee waived when you approve the repair

​

Service area: Denton, Krum, Sanger, Corinth, Lake Dallas, Shady Shores, Aubrey, Argyle, and Ponder — roughly 20 miles around Denton.

Frequently Asked Questions

How often should I change my HVAC filter in North Texas?

For a standard 1" filter, every 30–60 days during heavy-use months (May–September and December–February). Homes with pets, allergies, or heavy dust may need monthly changes. 4" or 5" media filters typically last 6–12 months.

Why does my AC freeze up in the summer?

The two most common causes are a dirty air filter or low refrigerant. Restricted airflow drops the coil below freezing. Change the filter first; if it re-freezes within a day, you likely have a refrigerant leak, which requires a licensed technician.

Should I reset a breaker that keeps tripping?

Reset it once. If it trips a second time, stop and call a professional. A repeatedly tripping breaker means a short circuit, a failing motor, or another fault that can start a fire.

Is it worth repairing an older AC or should I replace it?

Common rule: if the unit is more than 10–12 years old and the repair costs more than 30–50% of a new system, replacement usually makes more financial sense — especially with today's higher SEER2 efficiency ratings. We give free replacement quotes with no pressure.

Do you charge a diagnostic fee?

Yes, a flat diagnostic fee covers the technician's trip and a full system evaluation. The fee is waived if you approve the repair. Call 940-243-9199 for current pricing.

What areas do you serve?

Denton and surrounding North Texas communities: Krum, Sanger, Corinth, Lake Dallas, Shady Shores, Aubrey, Argyle, and Ponder — roughly a 20-mile radius from Denton.

Ready When You Are
 

Cogburn's Heating & Air Conditioning has served Denton families since 1999.

Honest recommendations, upfront pricing, same-day service.

​📞 (940) 229-6243

Cogburn's Heating & Air Conditioning · Denton, TX · 940-243-9199

Home · AC Repair · Heating · Maintenance Plans · Privacy

LIC# 11080 · © 2026 Cogburn's Service General dba Cogburn's Heating & Air Conditioning

Regulated by The Texas Department of Licensing and Regulation, P.O. Box 12157, Austin, Texas 78711, 1-800-803-9202, 512-463-6599, www.tdlr.texas.gov

bottom of page