Brand: Honeywell
Category: Thermostat
Manual Type:
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Manual for TH9421C1004 - Troubleshooting and error codes + PDF Download
Uploaded: April 8, 2025, 1:49 p.m.
Manual Publish Date: 2008-01-01
Warranty Summary
No warranty information found in this installation manual.
The Honeywell VisionPRO® IAQ TH9421C1004 is a touch-screen programmable thermostat designed for up to 4 Heat/2 Cool systems. Key operations include setting date and time, and installer setup for configuring zone number, year, month, date, schedule format, system type, compressor stages, fan control, and various advanced settings like dehumidification, ventilation, and error code handling. The installer setup is accessed by pressing and holding the 'SYSTEM' button for 5 seconds. The thermostat also features a system test mode to verify the functionality of cooling, fan, heating, emergency heating, humidifier, dehumidifier, and ventilator components.
Troubleshooting and error codes
| Error codes | Description |
|---|---|
| 027 | Faulty thermostat (must be replaced) |
| 035 | Duplicate thermostat zone detected |
| 036 | Duplicate UV timer |
| 037 | Duplicate filter timer |
| 038 | Duplicate humidifier pad timer |
| 039 | Duplicate indoor humidity sensor |
| 040 | Compressor should be running but it is not |
| 050 | Duplicate outdoor temperature sensor |
| 052 | Faulty post-coil air discharge sensor |
| 053 | Faulty outdoor temperature sensor |
| 054 | Faulty indoor humidity sensor |
| 089 | Heating/cooling equipment is missing |
| 090 | Data interface is continuously busy |
| 091 | Thermostat is not receiving data from other equipment |
| 118 | Faulty discharge air temperature sensor |
| 119 | Faulty temperature sensor |
| 121 | Duplicate post-coil air discharge sensor |
Troubleshooting and error codes
| Error codes | Description |
|---|---|
| 027 | Faulty thermostat (must be replaced) |
| 035 | Duplicate thermostat zone detected |
| 036 | Duplicate UV timer |
| 037 | Duplicate filter timer |
| 038 | Duplicate humidifier pad timer |
| 039 | Duplicate indoor humidity sensor |
| 040 | Compressor should be running but it is not |
| 050 | Duplicate outdoor temperature sensor |
| 052 | Faulty post-coil air discharge sensor |
| 053 | Faulty outdoor temperature sensor |
| 054 | Faulty indoor humidity sensor |
| 089 | Heating/cooling equipment is missing |
| 090 | Data interface is continuously busy |
| 091 | Thermostat is not receiving data from other equipment |
| 118 | Faulty discharge air temperature sensor |
| 119 | Faulty temperature sensor |
| 121 | Duplicate post-coil air discharge sensor |