Trane CVHE Chiller Alarm AFT2: Air Flow Transmitter Failure Diagnosis & Field Fix
Published: 2026-06-11
🔍 Symptoms Checklist
- ⚠️ Unit derates to 60% capacity automatically
- ⚠️ UC800 display shows 'AFT2 Sensor Fault'
- ⚠️ No visible damage to external wiring
- ⚠️ More frequent during high-humidity days or after heavy rain
🛠️ OEM Replacement Parts
| Part Name | OEM Part Number | Est. Price |
|---|---|---|
| Air Flow Transmitter Sensor Module | TRN-SEN04162 |
$420-580 |
| AFT2 Wiring Harness (sensor-to-UC800) | TRN-HAR08241 |
$95 |
| UC800 Controller Board (if sensor signal trace is damaged) | TRN-CTRL-UC800-MOD6 |
$2,800-3,500 |
📋 Interactive Diagnostic Procedure
Click each step to expand detailed diagnostic instructions. Follow in sequence — each step builds on the previous one.
Frequently Asked Questions
Can I run the chiller with AFT2 alarm active?
Yes, at 60% derated capacity. The chiller will continue to operate but cooling output is limited. Do not bypass the sensor — the derate is protecting the compressor from potential surge damage if actual flow is compromised. Repair within 48 hours.
Is AFT2 failure related to the chiller's age or operating hours?
More correlated with installation environment than age. Units in coastal areas, cooling tower plume zones, or high-humidity mechanical rooms see 3x the failure rate regardless of operating hours. Apply dielectric grease to the connector during preventive maintenance to extend sensor life.
🔗 Related Error Codes — Centrifugal Chillers
Other diagnostic guides in the same equipment category. Common failure patterns often share root causes — cross-referencing speeds up diagnosis.
Carrier 19DV Chiller Alarm 104: Centrifugal Compressor Surge Diagnosis
Alarm 104 on the Carrier 19DV centrifugal chiller indicates a compressor surge condition — a...
York YK Chiller Alarm: Compressor Surge & High Lift Protection
The York YK centrifugal chiller features an advanced surge protection algorithm that monitors...
Daikin WMC Chiller Alarm E3: Motor Overcurrent & VFD Fault
Daikin WMC chillers use oil-free magnetic bearing centrifugal compressors with integrated...
Trane CVHE Chiller Alarm 8D: Low Evaporator Refrigerant Temperature
Alarm 8D on the Trane CVHE centrifugal chiller indicates that the leaving evaporator water...
Carrier 19DV Alarm 102: Low Oil Pressure — Compressor Lubrication Failure
Alarm 102 on the Carrier 19DV centrifugal chiller indicates that the compressor's lubrication...
York YK Chiller Alarm: High Oil Temperature — Oil Cooler Performance
The York YK centrifugal chiller monitors oil sump temperature via an RTD sensor in the oil...
Trane CVHE Alarm 8A: High Condenser Pressure — Heat Rejection Failure
Alarm 8A on the Trane CVHE centrifugal chiller indicates that the condenser pressure has...
Carrier 19XR Alarm 125: Motor Bearing High Temperature — Hermetic...
Alarm 125 on the Carrier 19XR hermetic centrifugal chiller monitors the motor bearing...
⚡ Fault-Induced Energy Waste Estimator
When HVAC equipment runs with active error codes, it operates inefficiently and wastes electricity. Estimate the monthly cost of delaying repairs. All calculations run locally in your browser.
References & Industry Standards
- ASHRAE 15 — Safety Standard for Refrigeration Systems
- ASHRAE 34 — Refrigerant Designation & Safety Classification
- AHRI 550/590 — Water-Chilling & Heat Pump Packages
- SMACNA — HVAC Duct Construction Standards
- Manufacturer Service Manuals — Carrier, Trane, York, Daikin, Lennox