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12V DC Refrigeration Controller with Auto Defrost (STC-201)
Overview
12V DC Digital Temperature Controller for Refrigeration and Cooling Systems
YeloDeer STC-201 is a compact single-sensor digital temperature controller designed for 12V DC refrigeration and cooling applications. It automatically switches a compressor or cooling load on and off based on the detected temperature and your selected setpoint.
The controller combines temperature control, compressor restart delay, automatic or manual defrost, high and low temperature alarms, temperature calibration, and °C/°F display switching in one compact panel-mounted unit.
It is suitable for RV refrigerators, camper cooling systems, small freezers, portable cooling boxes, beverage coolers, display cabinets, cold storage cabinets, fresh-keeping cabinets, mushroom growing chambers, and other compatible 12V DC cooling applications.
Quick Fit Snapshot
Key Benefits
Best For
Important Before You Order
This controller requires a regulated 12V DC power supply.
Do not connect it directly to 120V or 240V AC power. Confirm the voltage, load type, current requirement, relay capacity, wiring method, and sensor placement before installation.
Use It For / Do Not Use It For
Important Load Note
The 30A compressor relay and 10A defrost relay ratings refer to resistive-load relay contact ratings under specified conditions.
Compressors, motors, fans, and other inductive loads may require a lower allowable working current. Use appropriate circuit protection and confirm the actual load specifications before installation.
General-Use Product Notice
This controller is intended for general temperature-control applications. It is not designed for life-support, medical compliance, pharmaceutical storage, or other critical systems where temperature failure could cause serious injury, loss, or regulatory noncompliance.
Applications
Recommended Applications
YeloDeer STC-201 is designed for compatible 12V DC refrigeration and cooling systems that require automatic temperature control, compressor protection, defrost control, and temperature alarms.
Compatibility Checklist
Compatible Cooling Loads
Cooling Control Example
Example: Set temperature = 41°F (5°C), temperature differential F1 = 3°F (3°C).
The cooling output turns on when the detected temperature reaches 44°F (8°C) and turns off when the detected temperature drops to 41°F (5°C).
When Not to Use This Product
- 120V or 240V AC-powered systems
- Applications that require direct mains-voltage switching
- Heating-only control applications
- Loads above the compressor or defrost relay ratings
- Compressors with unverified startup or inrush current
- Life-support equipment
- Medical refrigerators requiring certified monitoring
- Pharmaceutical or vaccine storage
- Critical food-storage systems without independent safeguards
- High-temperature or high-humidity environments
- Strong electromagnetic interference environments
- Corrosive environments
Sensor Placement Applications
If you are unsure whether your compressor, cooling fan, defrost load, or power supply is compatible, contact yelodeer@yelodeer.com with your system voltage, load current, startup current, wiring diagram, and application details.
Specifications
Product Specifications
| Model | STC-201 |
| Product Type | Digital temperature controller for 12V DC refrigeration and cooling systems |
| Power Supply | 12V DC |
| Sensor Type | NTC temperature sensor |
| Temperature Display Range | -50°C to 120°C (-58°F to 248°F) |
| Temperature Control Range | -40°C to 20°C (-40°F to 68°F) |
| Operating Ambient Temperature | -10°C to 60°C (14°F to 140°F) |
| Working Humidity | ≤80% RH, non-condensing |
| Compressor/Cooling Relay Rating | 30A resistive load |
| Defrost Relay Rating | 10A resistive load |
| Temperature Units | °C or °F selectable |
| Default Temperature Unit | °F |
| Cooling Output | Automatic relay control based on set temperature and differential |
| Defrost Control | Automatic interval defrost and manual defrost |
| Alarm Functions | High temperature, low temperature, and sensor-fault indication |
| Display | Digital real-time temperature and parameter display |
| Key Lock | Automatic key lock with manual unlock function |
| Warranty | 1-year limited warranty against manufacturing defects |
Advanced Parameter Table
| Code | Function | Setting Range | Default |
|---|---|---|---|
| F1 | Temperature Differential | 1–68 | 5°F / 5°C |
| F2 | Temperature Adjustment Lower Limit | -40 to set temperature | -4°F / -20°C |
| F3 | Temperature Adjustment Upper Limit | Set temperature to 68 | 68°F / 20°C |
| F4 | Compressor Start Delay | 0–10 minutes | 2 minutes |
| F5 | Temperature Calibration | -10 to 10 | 0°F / 0°C |
| F6 | Defrost Cycle | 0–24 hours | 6 hours |
| F7 | Defrost Duration | 0–60 minutes | 30 minutes |
| F8 | Display Mode During Defrost | 0 / 1 / 2 | 1 |
| F9 | High Temperature Alarm | F10 to 123°F / °C or OFF | OFF |
| F10 | Low Temperature Alarm | OFF to 45°F / °C or F9 | OFF |
| F11 | Alarm Differential | 1–20 | 2°F / 2°C |
| F12 | Temperature Alarm Delay | 0–60 minutes | 2 minutes |
| F13 | Temperature Unit | 0 = °C / 1 = °F | 1 |
Parameter Functions
Temperature Differential Example
With a 41°F (5°C) set temperature and an F1 differential of 3°F (3°C), cooling starts at 44°F (8°C) and stops at 41°F (5°C).
A larger F1 value creates fewer start-and-stop cycles. A smaller F1 value provides tighter temperature control but may increase compressor cycling.
Temperature Calibration Example
If the actual temperature is 50°F (10°C) but the controller displays 54°F (12°C), set F5 to -4°F (-2°C).
Calibrated temperature = detected temperature + F5.
Defrost Display Options
Temperature values are not automatically converted when switching between °C and °F. After changing the unit, review and reset the temperature setpoint and all temperature-related parameters.
Installation
Installation Overview
The STC-201 must be installed in a compatible 12V DC refrigeration or cooling system. Disconnect power before wiring and confirm all terminal functions before making connections.
- Disconnect all power to the cooling system.
- Confirm that the available power supply is regulated 12V DC.
- Confirm the compressor, fan, cooling load, and defrost-load ratings.
- Install suitable fusing or circuit protection.
- Mount the controller in a suitable panel opening or enclosure.
- Connect the 12V DC positive and negative power wires.
- Connect the cooling or compressor output according to the wiring diagram.
- Connect the defrost output if your system uses a compatible defrost load.
- Connect the NTC temperature sensor.
- Secure all terminals and insulate exposed conductors.
- Position the sensor in the controlled cooling area.
- Restore power and verify the real-time temperature display.
- Set the target temperature and advanced parameters.
- Test cooling, delay, alarm, and defrost operation before normal use.
Terminal Wiring Guide
| Terminal | Function | Description |
|---|---|---|
| 1 | Defrost Output | Negative-side output for the compatible defrost load |
| 2 | Unused | Leave unconnected on this 12V DC version |
| 3 | Power Input | 12V DC negative terminal |
| 4 | Unused | Leave unconnected on this 12V DC version |
| 5 | Compressor/Cooling Output | Negative-side output for the compatible compressor or cooling load |
| 6 | Unused | Leave unconnected on this 12V DC version |
| 7 | Shared Positive | 12V DC positive terminal shared by power input, cooling output, and defrost output |
| 8 | Unused | Leave unconnected on this 12V DC version |
| 9–10 | Temperature Sensor | Connect the external NTC temperature sensor |
Terminal 7 is the shared DC-positive terminal. It is shared by the controller power input, compressor/cooling output circuit, and defrost output circuit.
Terminals 2, 4, 6, and 8 are not used on this 12V DC version and must remain unconnected.
Important Installation Notes
Basic Temperature Setting
- Unlock the controller if the keys are locked.
- Press the SET button once. The SET indicator will turn on.
- Press the up or down button to adjust the target temperature.
- Press the lock/confirm button to save and exit.
Advanced Parameter Settings
- Unlock the controller.
- Press and hold the SET button and down button together for approximately 3 seconds.
- Press the up or down button to select the required function code from F1 to F13.
- Press SET to open the selected function.
- Press the up or down button to adjust the value.
- Press the lock/confirm button to save the setting.
Turning the Controller On and Off
Manual Defrost
Manual defrost can be used when excessive frost or ice forms before the next scheduled automatic defrost cycle, or when defrost must be activated for testing or maintenance.
Setting F6 or F7 to 0 disables automatic defrost. The defrost output stops automatically when the configured defrost duration ends.
Sensor Placement Guide
Incorrect sensor placement may cause inaccurate readings, frequent compressor cycling, unstable alarms, or poor temperature control.
FAQ
Product Basics
Is this controller for 12V DC systems only?
Yes. The STC-201 is designed specifically for 12V DC refrigeration and cooling systems.
Do not connect it to 120V or 240V AC power.
Can this controller operate a refrigerator compressor?
It can control a compatible 12V DC compressor or cooling load when the voltage, wiring, normal current, startup current, and relay requirements are suitable.
The 30A relay rating is a resistive-load rating. Compressors are inductive loads and may require a lower allowable operating current or an external switching device.
Can this controller be used for heating?
This model is designed around refrigeration and cooling control logic. It turns the cooling output on when the temperature rises above the setpoint plus the differential.
It is not recommended as a general heating thermostat.
Does the controller include a temperature sensor?
Yes. The controller uses an external NTC temperature sensor for real-time temperature detection.
Temperature and Compressor Control
How does the cooling control work?
The cooling output turns on when the detected temperature is greater than or equal to the set temperature plus F1.
The cooling output turns off when the detected temperature is less than or equal to the set temperature.
Why does the cooling output not start immediately?
The compressor start delay may be active. When the cooling indicator flashes, the controller is waiting for the F4 delay period to end.
This delay helps protect compatible compressors from rapid restart cycling.
How can I reduce frequent compressor cycling?
Increase the F1 temperature differential or increase the F4 compressor start delay.
Also check sensor placement, airflow, cabinet insulation, door sealing, and whether the sensor is exposed to rapid temperature changes.
Why is the displayed temperature inaccurate?
Check the sensor connection, sensor placement, airflow, nearby heat or cold sources, and whether the sensor is securely positioned.
If the difference is consistent, use F5 temperature calibration to match a trusted reference thermometer.
Why did my setpoint limits change?
F2 sets the lowest target temperature users can select, while F3 sets the highest target temperature.
Review F2 and F3 if the desired set temperature cannot be selected.
Defrost Questions
How does automatic defrost work?
F6 sets the number of hours between automatic defrost cycles, and F7 sets how many minutes each defrost cycle runs.
For example, F6 = 6 and F7 = 30 means defrost starts every six hours and runs for 30 minutes.
How do I disable automatic defrost?
Set F6 or F7 to 0. Either setting disables the automatic defrost function.
How do I start manual defrost?
Unlock the controller, then press and hold the lock button for approximately 3 seconds.
Press and hold the same button again for approximately 3 seconds to stop manual defrost.
Why does the display show “dEF”?
The controller is in a defrost cycle and F8 is set to display “dEF” during defrost.
After defrost ends, the display returns to normal after the delay period or when the cabinet temperature returns to the control range.
Why is frost building up too quickly?
The automatic defrost interval may be too long, the defrost duration may be too short, or the defrost load may not be working correctly.
Review F6, F7, the defrost wiring, the defrost load, door sealing, humidity, and operating conditions.
Alarm and Error Questions
How do the high and low temperature alarms work?
F9 sets the high-temperature alarm value, F10 sets the low-temperature alarm value, F11 sets the recovery differential, and F12 sets the alarm delay.
The alarm functions activate only after the compressor has started and stopped once.
Why is the temperature display flashing?
The detected temperature may have remained above the F9 high-temperature limit or below the F10 low-temperature limit longer than the F12 alarm delay.
Check the actual cabinet temperature, compressor operation, sensor placement, alarm parameters, and cooling performance.
What does “EE” mean?
“EE” indicates a temperature sensor fault.
Check the sensor connection, loose terminals, damaged sensor wiring, and sensor condition. Replace the sensor if necessary.
When the sensor fails, the controller uses timed operation: the compressor stops for 30 minutes and runs for 15 minutes.
Why do the keys not respond?
The controller may be locked. Press and hold the lock button to unlock it before changing settings.
Why did alarm values change after switching between °C and °F?
The controller does not automatically convert parameter values when changing temperature units.
After switching between °C and °F, review the set temperature, differential, limits, calibration, and alarm settings.
Wiring and Safety
Which terminals are unused?
Terminals 2, 4, 6, and 8 are not used on this 12V DC version and should remain unconnected.
Why is terminal 7 used by multiple circuits?
Terminal 7 is the shared 12V DC positive terminal for the controller power input, compressor/cooling circuit, and defrost circuit.
Follow the wiring diagram carefully and disconnect power before wiring.
Can I connect a 30A compressor directly?
Not automatically. The 30A rating applies to resistive-load relay contacts under specified conditions.
Compressors have inductive startup current that may exceed their normal running current. Confirm the compressor’s startup current and use an external relay, contactor, or driver when required.
What should I send when requesting technical support?
Please email yelodeer@yelodeer.com with:
- Photos of the controller and wiring
- Your 12V DC power-supply specifications
- Compressor or cooling-load model
- Normal running current and startup current
- Defrost-load specifications
- Current F1–F13 settings
- Displayed error or alarm condition
- Application and sensor-placement photos
Guides
Setup Checklist
Recommended Initial Settings Review
Quick Troubleshooting Guide
| Problem | Possible Cause | Recommended Action |
|---|---|---|
| Compressor or cooling output does not start | Set temperature is too high, F4 delay is active, or wiring is loose | Lower the set temperature, wait for the delay to end, and inspect the terminals |
| Cooling indicator is flashing | Compressor start delay is active | Wait until the F4 delay period ends |
| Defrost does not work | F6 or F7 is set to 0, the next cycle has not started, or defrost wiring is loose | Set F6 and F7 above 0, wait for the next cycle, and inspect the wiring |
| Frequent alarms | Alarm parameters are incorrect or sensor placement is poor | Review F9–F12 and reposition the sensor |
| Temperature display is inaccurate | Sensor placement is poor or calibration is needed | Reposition the sensor and adjust F5 |
| Display shows “EE” | Sensor fault, loose sensor connection, or damaged sensor | Check terminals 9–10 and replace the sensor if necessary |
| Keys do not respond | Controller is locked | Press and hold the lock button to unlock |
| Temperature cycles too widely | F1 differential is too large | Reduce F1 while avoiding excessive compressor cycling |
| Compressor cycles too frequently | F1 is too small, F4 is too short, or sensor placement is unstable | Increase F1 or F4 and improve sensor placement |
Safety Checklist
- Use only a regulated 12V DC power supply.
- Disconnect all power before wiring or maintenance.
- Do not exceed the 30A compressor or 10A defrost resistive-load relay ratings.
- Account for compressor and motor startup current.
- Use appropriate fuses, wire sizes, terminals, and external switching devices.
- Do not install in high-temperature, high-humidity, corrosive, or high-interference environments.
- Keep sensor wiring separated from power and load wiring.
- Do not use this controller as the only safeguard in critical storage applications.
Need Technical Help?
Contact yelodeer@yelodeer.com with your wiring photos, power-supply information, compressor specifications, current settings, and a description of the issue.