| Symptom | Problem | Action |
| OL (on display) | Target temperature out of range | Select a target within the metric range |
| -OL(on display) | Target temperature below range | Select a target within the metric range |
| low battery | Replacement battery. | |
| Display is blank | possible battery drain | Check and/or replace battery. |
| Laser not working | 1. Low battery or dead battery | 1. Replace the battery. |
| 2. The ambient temperature is higher than 40 degree (104 degree F) | 2. Suitable for areas with low ambient temperature | |
| long buzzer | Is there a function to set High/Low, | Reset or cancel limit settings. |
| and the measured value has exceeded the limit |
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infrared thermometer ST490 Product link:
