Pool Heater Not Working? Troubleshooting Guide for Gas, Heat Pump & Solar

A pool heater that won't work is frustrating, especially when Texas weather swings from 80°F to 40°F overnight. Most heater problems fall into a few categories: ignition failure, low flow, thermostat issues, or electrical faults. Many can be diagnosed at home before calling a technician, and some have simple fixes that take minutes.

Here's how to troubleshoot your pool heater by type and know when it's time for professional repair.

Gas Pool Heaters (Most Common in DFW)

Gas heaters (natural gas or propane) are the most popular pool heaters in the DFW area because they heat water fast regardless of air temperature.

Problem: Heater won't ignite

Check these first:

1. Is the gas supply on? Check the gas valve on the supply line — it should be parallel to the pipe (open), not perpendicular (closed)
2. Is the pilot light lit? (older models) Follow your heater's pilot lighting instructions
3. Is there an error code on the display? Write down any codes — they're diagnostic gold
4. Check the breaker — even gas heaters need electricity for ignition and controls
5. Is the filter clean and pump running? Most heaters have a flow switch that prevents ignition without adequate water flow

Common causes of ignition failure:

• Dirty or corroded igniter
• Failed ignition control module
• Low gas pressure
• Blocked exhaust or intake vents (bird nests, debris, spider webs are common in DFW)
• Wind blowing out the pilot (exposed heaters without wind guards)

Problem: Heater ignites but shuts off quickly

Common causes:

• Low water flow — dirty filter, closed valve, or undersized pump. The flow switch detects insufficient flow and shuts down the heater as a safety measure
• High limit switch tripped — water is too hot or the sensor is faulty
• Blocked heat exchanger — scale buildup from hard DFW water restricts flow through the heater
• Exhaust rollout — combustion gases not venting properly, triggering safety shutoff

Try this:

1. Clean or backwash your filter
2. Check that all valves between pump and heater are fully open
3. Let the heater cool for 15 minutes, then try again
4. If it keeps shutting off, the issue likely requires professional diagnosis

Problem: Heater runs but water isn't getting warm

Check:

• Thermostat setting — is it set high enough? For pool heating, set to desired temperature (typically 82-88°F)
• Heater size — an undersized heater can't keep up with heat loss, especially in cooler weather or if the pool isn't covered
• BTU output — older heaters lose efficiency. A 400,000 BTU heater from 2005 may only be outputting 300,000 BTU today
• Gas pressure — low gas pressure reduces heating capacity
• Wind and weather — uncovered pools lose massive amounts of heat at night

Gas heater error codes

Every manufacturer uses different codes, but common ones include:

• IF or IGN — Ignition failure
• FL or FLO — Low flow
• HI — High limit tripped
• PS — Pressure switch error
• AFS — Air flow switch fault

Write down your error code and heater model number. Contact us at (469) 455-1054 and we can often diagnose the issue over the phone.

Heat Pump Pool Heaters

Heat pumps extract heat from the air and transfer it to pool water. They're energy-efficient but slower than gas heaters and dependent on air temperature.

Problem: Heat pump won't turn on

Check:

1. Breaker — heat pumps run on 220V circuits. Check the breaker at the panel
2. Thermostat setting — set above current water temperature
3. Air temperature — most heat pumps stop working efficiently below 50°F air temperature
4. Flow switch — ensure pump is running and filter is clean
5. Timer — if the heat pump is on a timer, verify it's in the "on" window

Problem: Heat pump runs but doesn't heat

Common causes:

• Air temperature too low — below 50°F, heat pumps can't extract enough heat from the air
• Dirty evaporator coil — leaves, dirt, and debris block airflow across the coil. Clean with a garden hose
• Refrigerant issue — if the fan runs but air coming off the top isn't cold, refrigerant may be low (professional repair required)
• Undersized unit — heat pumps are sized for pool volume and temperature rise. An undersized unit will run constantly without reaching target temperature

Problem: Heat pump is icing up

Causes:

• Running in cold weather below the heat pump's operating range
• Low refrigerant charge
• Blocked airflow from debris or landscaping too close to the unit
• Defrost cycle malfunction

Fix: Ensure 24+ inches of clearance around the heat pump. Clean the coil. If icing persists, call for professional service.

Heat pump maintenance

• Monthly: Clean debris from around the unit and evaporator coil
• Seasonally: Check refrigerant sight glass, clean coil thoroughly
• Annually: Professional inspection of refrigerant charge, electrical connections, and heat exchanger

Solar Pool Heaters

Solar heating uses roof-mounted or ground-mounted panels to warm pool water using sunlight. Common as supplemental heating in DFW.

Problem: Solar heater isn't heating

Check:

1. Solar panels are getting direct sunlight — shading from new tree growth reduces output
2. Flow rate — solar panels need adequate water flow. Check the solar valve is open
3. Solar controller — if equipped, check that the controller is set properly and sensors are working
4. Check valve — prevents water from flowing backward at night. A stuck check valve blocks circulation
5. Panel condition — look for leaking panels, disconnected headers, or cracked tubes

Problem: Solar panels are leaking

Solar panel leaks are common as UV exposure degrades the panels over time.

Short-term fix: Solar panel patch kits can seal small leaks.

Long-term fix: Panel replacement. Solar panel lifespan is typically 10-20 years depending on material and UV exposure.

Products That Help

Pool thermometer — accurately monitor your water temperature to know if your heater is actually performing. Digital floating thermometers give the most accurate readings. Available at our Northlake store.

Solar pool cover / liquid solar blanket — reduces heat loss by up to 75%, making any heater dramatically more effective. A solar cover is the single best investment for pool heating efficiency. We carry covers and liquid blanket products at our store and online shop.

Scale inhibitor — DFW's hard water causes scale buildup inside heat exchangers, reducing heater efficiency and eventually causing failure. Monthly use of scale inhibitor protects your heater investment. Available at our store.

Heater Repair Costs in DFW

Repair	Typical Cost
Service call + diagnosis	$100-$200
Igniter replacement	$150-$300
Ignition control module	$200-$500
Flow switch replacement	$100-$250
Heat exchanger cleaning	$200-$400
Heat exchanger replacement	$800-$2,000
Thermostat replacement	$150-$350
Gas valve replacement	$250-$500
Heat pump fan motor	$300-$600
Heat pump compressor	$1,000-$2,500

When to Repair vs Replace

Repair if:

• Heater is under 8 years old
• Single component failure (igniter, thermostat, flow switch)
• Repair cost is under 50% of replacement cost
• No rust or structural corrosion

Replace if:

• Heater is over 10-12 years old
• Heat exchanger is leaking or severely scaled
• Multiple components failing
• Repair cost exceeds 50% of new heater price
• Heater is inefficient (high gas bills for low heat output)
• Upgrading to a more efficient system makes financial sense

New gas heater installation in DFW typically runs $2,500-$5,000 depending on size and brand. Heat pump installation runs $3,500-$7,000. We install all major brands including Pentair, Hayward, Raypak, and Jandy.

Professional Heater Service

Simplified Pools provides full heater diagnostics, repair, and installation across the DFW North area. Our repair technicians service gas heaters, heat pumps, and solar systems.

• Same-week repair appointments available
• 1-year warranty on all repair work
• Free diagnostic with approved repair
• All major brands serviced

Schedule a heater repair or call (469) 455-1054. We serve Northlake, Argyle, Flower Mound, Trophy Club, Justin, Roanoke, Krum, Ponder, Bartonville, Westlake, and surrounding areas.

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Need heater repair in DFW North? Simplified Pools offers same-week service with a 1-year warranty. Contact us or visit our store at 1611 Commons Cir Suite 100, Northlake, TX 76226.