What does the TXV do?
It's a precision brass valve that meters liquid refrigerant into your indoor coil based on demand. Think of it as the carburetor for your AC's refrigerant flow.
San Antonio · TXV Replacement Repair · Family-Owned Since 1996
If Your Cooling Is Weak But The Refrigerant Charge Is Perfect, It's Probably The TXV.
The TXV is the brass valve that meters refrigerant into your indoor coil. When it fails (open or stuck closed), no amount of recharging will fix the cooling — it has to be replaced.
Typical price
$549–$895
Time to fix
3–4 hours
Urgency
Medium-high — keeps system running inefficient until fixed
In plain English — what's going on with your txv replacement
The thermostatic expansion valve (TXV) sits at the inlet of your indoor evaporator coil. Its job is to meter exactly the right amount of liquid refrigerant into the coil based on demand. When it works, your system runs efficient and your superheat stays in a tight range.
TXVs fail two ways: stuck open (too much refrigerant floods the coil, you get high superheat, weak cooling, possible compressor flooding) or stuck closed (starving the coil, frozen coil, no cooling at all). Both feel like 'low refrigerant' but recharging won't help.
Diagnosis takes a real tech with gauges who knows superheat/subcool relationships. Replacement is $549–$895 — the valve itself is $80–$200, but it requires recovering refrigerant, brazing in the new valve under nitrogen purge, pulling a deep vacuum, and recharging to spec.
What it costs in San Antonio
$549–$895 — Includes new TXV, brazing labor, nitrogen purge, vacuum, and refrigerant recharge to factory spec. Our $59 diagnostic is waived when you approve the repair, so you only pay for the fix itself.
Symptoms you'll notice at home
If two or more of these sound familiar, it's probably your txv replacement.
Weak cooling despite correct refrigerant charge
High superheat readings at the suction line
Indoor coil frosting up randomly
Hissing sound from the indoor air handler
Inconsistent cooling — works fine one day, weak the next
Compressor running very hot or short-cycling on high pressure
Why txv replacements fail in San Antonio
- Contamination in the refrigerant from a previous compressor burnout.
- Moisture in the system from poor brazing or skipped vacuum on a prior repair.
- Age and wear — most TXVs last 10–15 years.
- Sensing bulb falling off the suction line or losing its charge.
- Manufacturing defects in certain model years/brands.
How we diagnose and replace it
Here's exactly what a Carnes and Sons tech does at your house — no mystery, no upselling.
- 1
Measure superheat and subcool
We take pressure and temperature readings and calculate both. A failed TXV has a very specific fingerprint — high superheat with normal subcool means TXV starvation, low superheat means TXV flooding.
- 2
Inspect sensing bulb mount and insulation
Sometimes the fix is just re-securing the sensing bulb to the suction line. We check that first before condemning the valve.
- 3
Recover refrigerant and braze in new TXV
Full refrigerant recovery, cut out the old valve, braze in new one under nitrogen purge to prevent oxidation inside the lines.
- 4
Vacuum and recharge to spec
Pull a deep 500-micron vacuum to remove moisture, then weigh in refrigerant to factory data plate. Verify with superheat/subcool readings before leaving.
What Your Neighbors Are Saying
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TXV Replacement questions San Antonio homeowners actually ask
How do I know if my TXV is bad?
Weak cooling with a correct refrigerant charge is the biggest clue. We confirm with superheat and subcool readings — TXV failures have a specific fingerprint that a real tech with gauges can spot in 15 minutes.
Can the TXV be cleaned instead of replaced?
Sometimes — if the failure is from light contamination, a flushing kit can save it. Most of the time it's worn out and replacement is the right answer. We try cleaning first if it's a candidate.
How much does TXV replacement cost?
$549 to $895 in San Antonio. The part is cheap ($80–$200), but the labor is intense — recover refrigerant, braze the new valve in under nitrogen, vacuum the lines, and recharge to spec.
How long does TXV replacement take?
3 to 4 hours done right. Anyone promising it in an hour is skipping the nitrogen purge or the proper vacuum — both shortcuts will destroy the new valve within a year.
Is TXV covered under warranty?
Usually yes if the system is under 10 years old and you have proof of regular maintenance. We'll check your warranty before quoting and pass through any covered parts cost.
What's the difference between TXV and a fixed orifice?
TXV adjusts refrigerant flow in real-time; a fixed orifice (piston) is just a hole drilled to one size. Most newer high-SEER systems use TXVs because they're more efficient. Older base models often use orifices.
Will replacing the TXV fix my cooling?
If TXV is the actual problem, yes — immediately and dramatically. We always confirm with measurements before condemning the valve, because replacing one that's working won't help.
Serving txv replacement repairs across the greater San Antonio area
We're based in Stone Oak and roll trucks across San Antonio and the surrounding Hill Country every day.
Carnes and Sons Air Conditioning
License TACLB29435E · Family-Owned Since 1996
401 E Sonterra Blvd Suite 375
San Antonio, TX 78258(210) 600-5091
San Antonio, TX 78258(210) 600-5091
Mon–Sat: 7AM – 8PM · Emergency same-day service
Cities & neighborhoods we serve
San Antonio · Stone Oak · Alamo Heights · Hollywood Park · Hill Country Village · Shavano Park · Castle Hills · Leon Valley · Helotes · Boerne · Fair Oaks Ranch · Bulverde · Timberwood Park · Garden Ridge · Schertz · Cibolo · Selma · Universal City · Live Oak · Converse · Windcrest · New Braunfels
Talk to a real person about your txv replacement
No call center. The owner or one of his sons picks up.
(210) 600-5091