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What This Guide Helps With
This guide helps troubleshoot a SureTemp Plus 692 that does not complete a temperature measurement and instead displays “LO”, “HI”, or fails to read at all. These indications often happen when the instrument cannot detect a valid patient temperature or when it’s operating outside of its measurement range or environmental limits. The focus here is on simple, external checks and systematic isolation of common causes before assuming internal failure.
Step-by-Step Troubleshooting
Verify Correct Probe and Probe Cover
- Ensure you are using a Welch Allyn-approved disposable probe cover on the appropriate probe. Using incorrect or no cover can cause inaccuracies or failed readings.
- Confirm the correct probe type (oral/axillary or rectal) is installed for the intended measurement site.
Check Probe Seating and Connection
- Remove the probe from the probe well and then firmly reseat it until it clicks.
- Inspect the probe cable and connector for damage, kinks, or corrosion.
- A poorly seated or damaged probe often prevents valid readings.
Inspect Ambient Conditions
- Make sure the thermometer and probe are within their operating temperature range. If the ambient temperature is too low or too high, the device may display an error instead of reading. Move the device into a normal room environment and allow it to stabilize for a few minutes.
Battery Check
- Weak batteries can cause erratic behavior or failure to complete prediction cycles. Replace all three AA batteries with fresh alkaline batteries and retry.
Try a New or Known‑Good Probe
- If available, swap in a different Welch Allyn probe and well assembly. Probe thermistors can fail or drift, leading to LO/HI readings; a good probe will isolate whether the probe assembly or the main unit is at fault.
Confirm Proper Measurement Technique
- Ensure the probe is in firm contact with the patient’s tissue and held steadily during the measurement cycle.
- If taking axillary temperatures, the arm should be snug against the body to minimize ambient air exposure.
Attempt a Cycle Reset
- Eject the probe from the well and then reinsert it. This can sometimes “reset” the measurement cycle and clear transient errors.
Check for Device Security States
- Model 692 has security features that can disable operation (e.g., temperature count exhausted) showing messages rather than temperatures. Refer to the manual if SEC or other security indicators appear.
If the Problem Persists
If after following all the steps above the unit still will not take a reading or remains stuck on “LO”/“HI”, then common external causes have been ruled out:
- The thermometer’s internal electronics or heater/thermistor circuitry may be faulty.
- The main board or measurement circuitry could require bench evaluation.
Do the following:
- Remove the unit from service.
- Label it Out of Service.
- Send for authorized repair or bench evaluation.
Attempting internal board‑level repair is not appropriate for clinical engineering troubleshooting and may void warranties or compromise safety.
Clinical Use Tip
Never troubleshoot this device on an actively monitored patient. If the unit fails to take a measurement, move the patient to another verified working thermometer first, then troubleshoot the faulty unit.
Work Order Documentation (CCR Method)
CCR = Complaint, Cause, Resolution
Complaint
What was reported by the clinical staff.
Example:
“User reports that the SureTemp Plus 692 displays “LO”/“HI” and fails to complete a temperature reading.”
Cause
What was observed during troubleshooting.
Example:
“Verified poor probe contact, out‑of‑range ambient conditions, and low batteries were ruled out; error remained after trying a known‑good probe and fresh batteries.”
Resolution
What action was taken.
Example:
“Unit removed from service, labeled Out of Service, and sent to authorized service center for repair.”
Helpful Details to Include (If Known)
- Alarm behavior
- Probe type used
- Battery status
- Environmental conditions
- Final device status
Final Thought
Always approach thermometer issues by starting with simple external checks — probes, batteries, environment, and measurement technique — before moving to escalation. Documentation not only satisfies regulatory expectations but supports trend analysis for recurring issues.
That is successful troubleshooting.