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Thermostats
The Smallest Part of the System Causes a Surprising Share of the Calls
A thermostat is a switch with opinions. It decides when the compressor starts, when the second stage kicks in, when a heat pump gives up and turns on the electric strips, and how long the fan runs after a cycle. Get any of that wrong and the system misbehaves in ways that look like an equipment fault: short cycling, a house that is never quite the right temperature, a winter electric bill that doubles because auxiliary heat is running every night. We trace a lot of “broken AC” calls in Austin and San Antonio back to a thermostat that was wired for a different kind of system than the one on the wall.
Radiant installs smart thermostats, programmable thermostats and straightforward digital replacements, and the part that matters is the match. A heat pump needs a thermostat that can control the reversing valve and stage the backup heat. A two-stage furnace or variable-speed air handler needs one that can call for each stage. Many smart thermostats need a common wire for power that older homes never had. Our technician confirms what your equipment needs, runs or adapts the wiring, sets the configuration for your system and shows you how to use it before leaving.
If the thermostat is part of a bigger problem, we will say so. A new thermostat will not fix a failing compressor or a house that is hot upstairs because of thin attic insulation, and we would rather tell you that than sell you one.
- Wired for your equipment Heat pump, two-stage, variable-speed or single-stage: we configure the thermostat to match, not to the default.
- Set up before we leave Connected to your Wi-Fi, schedules built, and a walk-through so you are not reading a manual at 10 p.m.
- Home Comfort Guarantee A written price first, and if the issue cannot be resolved, a 10% inconvenience refund up to $1,000.
What to Watch For
Signs the Thermostat Is the Problem
Any of these is worth a look before assuming the equipment is at fault.
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A blank or flickering screen
Dead batteries, a lost common wire, a tripped float switch in the attic or a blown low-voltage fuse on the control board. Only one of those is the thermostat.
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The number on the wall never matches the room
A thermostat in a hallway, in sunlight or above a lamp reads its own little climate. Relocation or a remote sensor fixes it.
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The system starts and stops every few minutes
A wrong cycle-rate setting, a thermostat wired for the wrong equipment type, or a heat anticipator on an old unit set badly.
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A winter electric bill that jumped
On a heat pump, a thermostat that calls for auxiliary heat too early runs the electric strips all night. A configuration fix, not a new system.
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The fan never stops, or never starts
Fan set to “on” instead of “auto” is the easy one. A miswired G terminal or a stuck relay is the one that needs a meter.
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You replaced the system and kept the old thermostat
A new two-stage or heat pump system on a single-stage thermostat runs in one mode and never delivers what you paid for.
What We Install
Thermostat Installation, Replacement and Repair
From a straightforward digital swap to a smart thermostat with room sensors on a multi-stage system.
- Smart thermostat installation Wi-Fi thermostats with scheduling, remote control and learning features, wired and configured for your specific system.
- Programmable and digital replacements A reliable, accurate thermostat without the app, for homeowners who want set-and-forget control.
- Heat pump and multi-stage setup Reversing valve, staging and auxiliary heat lockout configured so the strips run only when they should.
- Common wire and low-voltage wiring Adding a C wire, repairing chewed or broken thermostat cable in the attic, and replacing blown control fuses.
- Relocation and remote sensors Moving a badly placed thermostat, or adding sensors so the system averages the rooms you actually use.
- Thermostat troubleshooting Blank screens, wrong readings and short cycling diagnosed at the thermostat, the wiring and the board, whichever is at fault.
How It Works
What a Thermostat Visit Looks Like
Usually under two hours, and you leave knowing how to use it.
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We check the equipment first
What kind of system you have, how many stages, and what the existing wiring supports. That decides which thermostats will work.
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You pick from written options
Smart, programmable or standard, with the price of each including any wiring work. Honored for 72 hours.
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Install and configure
Wired, powered, set for your equipment type and staging, connected to Wi-Fi and tested through a full heating and cooling cycle.
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A real walk-through
Schedules built around your week, the app on your phone, and the two or three settings that matter explained in plain language.
Current Specials
Save on the work your home needs most.
Ready for a Better Thermostat?
Installed and configured by a licensed technician, with a written price first.
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!!😊😊
★★★★★
Alex performed the winter service on my unit. This business along with Alex, are very professional and upfront about everything. To be transparent, this is the maintenance included with the purchase of a unit from them. I was informed about everything to include pictures as proof. I was told that my unit is 100% and very clean and again pictures to prove it. I was reccomended this business by a friend and glad he did. The initial purchase experience was also amazing. I had contacted 5 other businesses to get quotes about a new unit as my upstairs unit failed. 2 were outrageous quotes and I am technically still waiting on the other 3. On every instance of getting a quote, I waited about 1 week. Luckily my house has two units but still, un acceptable especially during the summer. I guess they all had so much business they did not care for mine. When I called this business not only did they come out the same day, I had the new unit installed with in 48 hrs. Oh and let's not forget the quote they gave me was the lowest of all. I can say enough good things about this business. Keep up the great work.
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
Thermostat Questions
Will a smart thermostat work with my system?
Usually, but not always straight out of the box. Three things decide it. First, power: most smart thermostats need a common wire, and a lot of Central Texas homes built before the 2000s have a four-wire cable with no spare, so a C wire has to be added or an adapter installed at the air handler. Second, equipment type: a heat pump needs a thermostat that controls the reversing valve and stages the electric backup heat, and a two-stage furnace or variable-speed system needs one that can call for each stage. Third, the odd cases: some older systems, line-voltage heaters and certain proprietary communicating systems need their own control. We check all three before recommending a model.
Why does my thermostat read one temperature when the rooms feel different?
Because it only measures the air around itself. A thermostat in a central hallway with no vents, or on a wall that gets afternoon sun, or above a lamp or a TV, will satisfy long before the bedrooms do, or run long after they are comfortable. In a two-story house the problem is bigger: a thermostat downstairs has no idea the upstairs is 82. The fixes are a better location, remote room sensors that let a smart thermostat average the rooms you use, or in a larger home a zoning setup. If the imbalance is severe, the cause may be ductwork or insulation rather than the thermostat, and we will tell you which.
Can a smart thermostat really lower my energy bill in Texas?
It can, if you let it do the one thing that saves money: run the system less when nobody needs it. Setting back a few degrees while the house is empty in August, and letting it recover before you get home, is where the savings come from. A thermostat that is simply set to 72 all day, every day, saves nothing. The other real saving is on heat pumps, where a smart thermostat configured correctly keeps the electric backup strips from running when the heat pump alone could carry the load. We do not quote a percentage, because it depends entirely on how you use it, but a schedule that fits your week is a good start.
What is the difference between a smart, programmable and standard thermostat?
A standard digital thermostat holds one setpoint until you change it. A programmable thermostat lets you set different temperatures by time of day and day of week, so the system eases off while you are at work and asleep. A smart thermostat does that and adds Wi-Fi: control from your phone, schedules it learns or adjusts on its own, room sensors, and alerts when something is wrong, like a filter reminder or a system that is running but not reaching setpoint. Which one is right depends on how you live. Someone home all day on a fixed routine may be well served by a programmable model; someone with a variable schedule or a second home gets real value from the smart features.
Why did my thermostat screen go blank?
Start with batteries if it has them. If it is powered by the system, a blank screen means the 24-volt supply from the air handler has stopped, and the common causes are a tripped float switch in the attic drain pan, a blown low-voltage fuse on the control board, a tripped breaker, or a thermostat wire that has been chewed or pulled loose in the attic. In summer, the float switch is the usual culprit: the condensate drain has clogged, the pan filled, and the switch cut power to protect your ceiling. That is a drain problem, not a thermostat problem, and clearing it restores everything. If the screen is blank and there is water in the pan, call us before resetting anything.
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