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San Antonio Furnace Maintenance
The Damage Is Done in August, Not January
A San Antonio furnace gets its first real test on a November night when half the city turns the heat on within the same hour. How that goes was decided months earlier, in an attic that spent July and August well above 120 degrees. That kind of heat dries out wire insulation, cooks control boards and leaves a film of oxide on the flame sensor. Dust, live oak pollen and cedar pollen drift onto the burners and the blower wheel. Wasps build in the flue. A furnace that ran perfectly last February can carry all of that into the fall without a single visible sign, because nothing has asked it to light.
A fall tune-up asks it to light on purpose, in daylight, with a technician watching the ignition sequence and a combustion analyzer in the flue. It is also the one time each year someone checks the heat exchanger and venting on a gas furnace, which matters more than comfort does: winter is when the house is shut tight and carbon monoxide has nowhere to go. We service closet furnaces in the 1950s and 60s homes around Alamo Heights and our Wye Drive office, attic furnaces in Stone Oak and Alamo Ranch, and the heat-strip air handlers of Converse and Schertz, and we have since 1999 under Texas HVAC license TACLB138286E.
The complete tune-up checklist is on our furnace maintenance page. What follows is why the visit matters more in San Antonio than the mild winters suggest, and what we look for here.
- Safety before comfort Heat exchanger, venting and carbon monoxide are checked on every gas furnace before we touch anything else.
- Timed for the first front October and early November, after the air conditioner has finished its year and before the first norther asks the furnace to work.
- Covered by Care Club For $9.99 a month, an enrolled system gets both of its yearly HVAC tune-ups, and members take 5% off repairs with priority scheduling.
Overdue?
How a Furnace Tells You It Wants a Look
None of these is an emergency by itself. Each is a reason to book the tune-up now instead of finding out on a cold night.
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Nobody has serviced it since you bought the house
The home inspection confirmed it turned on. It did not measure gas pressure, test the safeties or look inside the heat exchanger.
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The first-run smell lasted days, not an hour
A short burnt-dust smell is normal. One that lingers means a heavy buildup on the burners or heat exchanger, or something overheating.
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Last winter it took a few tries to light
A flame sensor or igniter on its way out. It will not have improved over the summer, and it is a small part today.
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The filter is grey and bowed inward
A starved blower runs hot, and on a furnace that trips the limit switch. The same filter has been catching pollen all cooling season.
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It rumbles or bangs a second after it lights
Delayed ignition from dirty burners. Gas collects, then lights all at once. Cleaning the burners at a tune-up fixes it.
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The rooms at the end of the ducts stayed cold last year
Low airflow from a dirty blower wheel or a duct that has come loose in the attic. We check both while the furnace is running.
The Fall Checklist
What We Check on a San Antonio Furnace Tune-Up
Measured with instruments and written down. You get the readings, not a thumbs-up.
- Flame sensor and igniter The sensor is cleaned of the oxide that builds up in an idle season and the igniter is checked for cracks and resistance. These two cause more no-heat calls than anything else.
- Heat exchanger and combustion Inspected for cracks and corrosion, with carbon monoxide measured in the flue and at the registers while the furnace runs.
- Venting and draft Flue slope, joints and clearances, and a check for the wasp nests and debris that block a vent over a Texas summer.
- Gas pressure and burners Manifold pressure set to the manufacturer’s number and burners cleaned so the flame is blue and even across all of them.
- Filter and blower A new filter, the blower wheel cleaned of a season’s dust, and motor amp draw and capacitor readings recorded.
- Safety controls Limit switch, pressure switch and flame rollout tested so the furnace shuts itself down the way it should if something goes wrong.
- Heat strips and thermostat On electric furnaces and heat pumps, each strip is amp-tested and the sequencer checked. On every system, the thermostat is confirmed to be calling for heat correctly.
About an Hour
A Fall Furnace Tune-Up, Step by Step
One system takes roughly an hour. You are welcome to watch, ask questions or leave us to it.
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Book it in October
Before the first front, when the schedule is open. Care Club members go to the front of the line and never pay a dispatch fee.
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Fire it and watch
A full ignition sequence with the analyzer in the flue and the panels off, so we see how the furnace actually behaves rather than assuming.
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Clean, adjust, measure
Sensor and burners cleaned, gas pressure set, filter replaced, blower and safeties tested, every reading written down.
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The report
What passed, what is wearing, and what can wait until spring. If something needs replacing, you get a written price and the decision is yours.
Current Specials
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Has Your Furnace Been Checked This Fall?
An hour in October beats a cold night in January.
What Our Customers Say
Don't just take our word for it — hear from our satisfied customers
★★★★★
Our 18 year old HVAC system finally gave out this past week, so we reached out to Radiant to see what could be done. They sent a tech out named Bryan the same day, and he did a great job looking over the entire HVAC system. He was friendly and helpful in explaining everything that he saw, and our options moving forward. We decided to replace the entire system, so we met with Jacob (same day thankfully) to find the best HVAC system for our needs. Jacob was friendly, professional, and did a great job explaining the different options on offer. Radiant was able to set-up next day install, which was much appreciated, because the temps were still going to be cold in the coming days.
The install team consisted of Carlos and Pablo, who were very courteous and professional, and were kind enough to answer any questions I had regarding the install. They did a great job installing our new HVAC system, and were tidy which is always appreciated! Before they left, they explained everything that had been done, and showed me photos of the work.
Our entire experience from start to finish was great. I appreciate that they send photos of who is coming to your home too. Friendly, kind, professional team members, and good work all the way around. Thanks Radiant!
The install team consisted of Carlos and Pablo, who were very courteous and professional, and were kind enough to answer any questions I had regarding the install. They did a great job installing our new HVAC system, and were tidy which is always appreciated! Before they left, they explained everything that had been done, and showed me photos of the work.
Our entire experience from start to finish was great. I appreciate that they send photos of who is coming to your home too. Friendly, kind, professional team members, and good work all the way around. Thanks Radiant!
★★★★★
This is the first time I’ve used radiant my neighbor recommended them…. I called them today and they set me up an appointment on the same day. I was totally shocked at that and the service call was only $39!!…. Highly recommend them Danielle showed up and he was a great guy and he put up with all my wishy-washiness and I had to hurry him because I was heading to church and he got caught in a lot of traffic getting here he even would’ve installed the part that broke but I Didn’t have the time tonight….. He was patient with me and just told me to call the office first thing in the morning and get a service call set up…. Thank you so much Radiant!!….
With another cold front coming in tomorrow now I just hope they can get me scheduled for a separate call tomorrow but I have a feeling they will. They are such a great company!!😊😊
With another cold front coming in tomorrow now I just hope they can get me scheduled for a separate call tomorrow but I have a feeling they will. They are such a great company!!😊😊
★★★★★
My unit had been acting funky for a bit and then decided it would shed its mortal coil and go to the next life. I called an another company lets call them company A since I had a warranty with them thinking I could save a few bucks. They showed up 2 hours late of given window. Warranty didnt cover any of the perceived issues ( not really their fault, maybe). Double billed me (why pay 700 for a service call when you can pay 1400!!! ie: they ran my card twice) and then even though issue still wasnt fixed wanted to upsell me some more for close to 3k or get another sweet unit for an overpriced amount.
I'll admit I was getting desperate. Do I let the giant commercial bad guys win? Give them all my money I could be using on fishing gear? My neighbor happens to work at Schmidt Mechanical Group (shout out to Jared) and got me in touch with their service technicians for a 2nd opinion. ENTER Richard Moreno. Showed up at the beginning of time window. Diagnosed the multiple issues in a timely manner. Explained to me what was going on and why and hand held me through what needed to be done now and what to expect in the future. Worked on both of my units. My bill came to a FRACTION of what was recommended by company A. Mr. Moreno was very professional, kind, and honest. As a first time home owner whos been bamboozled by companies like company A, Schmidt Mechanical Group just gained a customer for life. Look forward to doing more business with them and their techs are awesome. Dont be like me and use company A first. Use this company.
I'll admit I was getting desperate. Do I let the giant commercial bad guys win? Give them all my money I could be using on fishing gear? My neighbor happens to work at Schmidt Mechanical Group (shout out to Jared) and got me in touch with their service technicians for a 2nd opinion. ENTER Richard Moreno. Showed up at the beginning of time window. Diagnosed the multiple issues in a timely manner. Explained to me what was going on and why and hand held me through what needed to be done now and what to expect in the future. Worked on both of my units. My bill came to a FRACTION of what was recommended by company A. Mr. Moreno was very professional, kind, and honest. As a first time home owner whos been bamboozled by companies like company A, Schmidt Mechanical Group just gained a customer for life. Look forward to doing more business with them and their techs are awesome. Dont be like me and use company A first. Use this company.
Maintenance Membership
Join the Care Club
Home maintenance for $9.99 a month.
Care Club members get two HVAC tune-ups and a plumbing safety inspection every year, priority scheduling, no dispatch fees — ever — and 5% off every repair.
- Priority scheduling
- Seasonal HVAC tune-ups
- Annual safety inspection
- Exclusive member discounts
- Free dispatch on repairs
- No long-term contracts
San Antonio Furnace Maintenance Questions
What month should a San Antonio furnace tune-up happen?
October or early November is ideal. The air conditioner has usually finished its season by then, the first real cold front has not arrived, and there is time to order a part if the tune-up finds something failing. It is also when the schedule is easiest, because once the first norther comes through, tune-up slots compete with no-heat calls across Bexar County. If fall got away from you, a December or January visit still beats skipping the year; the furnace has simply had fewer chances to fail before we see it. Care Club members get the fall visit as one of the plan’s two yearly HVAC tune-ups, and priority scheduling once the rush starts.
Why check for carbon monoxide when the furnace barely runs?
Because a furnace that sits idle is the one most likely to have a problem nobody has noticed. A heat exchanger can crack from years of expansion and contraction, a flue can be blocked by a wasp nest or a bird from the summer, and a vent connector can separate in an attic. None of that matters until the burners light, and when they do the house is closed up against the cold with everyone asleep inside. At a tune-up we inspect the exchanger, measure carbon monoxide in the flue with a combustion analyzer, and check the air at the registers and around the furnace. We also recommend a working CO alarm near the bedrooms regardless of what we find. It is a cheap backstop for the one furnace fault that can hurt you.
My home has heat strips instead of a gas furnace. Is a fall tune-up still worth it?
Yes, and in a hard freeze it can matter more. Electric furnaces and heat pumps on the northeast side and in Converse, Schertz and Cibolo rely on resistance heat strips for the coldest nights, and those strips can burn out or lose a sequencer without any sign until they are needed. During February 2021, a lot of the homes that went cold had strips that had quietly failed years earlier. On a fall visit we amp-test each strip, check the sequencers and breakers, confirm the thermostat stages auxiliary heat correctly and, on a heat pump, run the defrost control and reversing valve. There is no combustion to check, so the visit is quicker, but the parts that keep you warm in a freeze all get exercised. Our San Antonio heat pump page goes into the winter side of those systems.
Will a tune-up tell me whether my old furnace can make it through another winter?
It will tell you what is failing now and what is wearing, which is as close to an answer as anyone honest can give. A cracked heat exchanger is a clear no: that furnace is done, and we will show you the crack rather than ask you to take our word. A weak igniter, a marginal capacitor or a tired blower motor are parts we can price in writing, and a furnace with one of those is usually worth keeping. What a tune-up cannot do is promise that a 20-year-old furnace has no other surprises in it. If the equipment is at that stage, we will say so and give you replacement numbers to compare, with no pressure either way. Care Club members pay 5% less on any repair we recommend, and our San Antonio furnace installation page explains what a replacement involves.
*Offers cannot be combined with other promotions or applied to dispatch fees. No cash value. Must present offer at time of service. Call for details.
