Thermometers · SureTemp family

Welch Allyn SureTemp Plus: troubleshooting and error codes

The ServiceForge knowledge base holds 12 documented symptoms for the Welch Allyn SureTemp Plus, with 14 ranked causes, 18 diagnostic checks with test points and expected values, and 26 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Patient temperature out of range patient safety

Display shows body outline with blinking up/down arrow and thermometer; measured patient temp outside limits

Ranked causes

1. Probe not properly positioned on patient (common)
2. Actual patient temperature outside normal limits (occasional)
3. Probe defect (occasional)

First check

Visually verify probe placement on patient

Test point: Probe tip contact point
Expected: Firm direct contact with patient skin/tissue

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Ambient temperature out of range

Display shows 'A' with blinking up/down arrow and thermometer; device measures out-of-range ambient

Ranked causes

2. Probe malfunction at high temperature (occasional)

First check

Verify ambient temperature

Test point: Device location
Expected: 50°F to 110°F (10°C to 43.3°C), 50–110°F / 10–43.3°C

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Ambient temperature too low (Av!)

Display shows 'A' with downward arrow and thermometer; ambient below minimum

Ranked causes

1. Ambient temperature below minimum (occasional)

First check

Verify ambient temperature reading

Test point: Device environment
Expected: ≥50°F (≥10°C), 50–110°F / 10–43.3°C

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery above operational range

Display shows blinking battery frame, 'b' symbol, and upward arrow when battery voltage exceeds 5.375V.

Ranked causes

1. Battery voltage high (occasional)

First check

Check battery voltage

Test point: Battery
Expected: ≤ 5.375 V

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery below operational range

Display shows blinking battery frame, 'b' symbol, and downward arrow when battery voltage drops below 3.00V.

Ranked causes

1. Battery voltage low (common)

First check

Check battery voltage

Test point: Battery
Expected: ≥ 3.00 V

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery low warning

Single blinking battery segment in indicator; battery approaching minimum operational voltage

Ranked causes

1. Battery approaching depletion (common)

First check

Check battery indicator segments

Test point: Battery display frame
Expected: Full segments or single blinking segment (low warning)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery voltage above operational range

Display shows blinking battery frame with 'b' and upward arrow; device may malfunction

Ranked causes

1. Battery voltage too high (b^) (occasional)

First check

Verify battery voltage output

Test point: Battery terminals
Expected: < 5.50 volts V, < 5.50 V

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery voltage below operational range

Display shows blinking battery frame with 'b' and downward arrow; device may not function

Ranked causes

1. Battery voltage too low (bv) (common)

First check

Verify battery voltage reading on display

Test point: Battery indicator frame
Expected: ≥3.1 volts (and <5.50 volts) V, >= 3.1 V and < 5.5 V

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Stored thermometer reactivation

Twelve-month maintenance for thermometers in extended storage before returning to service

Ranked causes

1. Routine twelve-month stored unit maintenance interval (common)

First check

Remove batteries

Test point: battery compartment
Expected: batteries removed and stored separately

2 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: SureTemp Plus thermometer

Six-month preventive maintenance calibration testing per Power-On Self Test and Model 9600/9600 Plus Calibration Testing procedure

Ranked causes

1. Routine six-month calibration interval (common)

First check

Visual inspection for physical damage

Test point: entire thermometer exterior
Expected: no cracks, dents, or damage

3 more checks with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Instrument error with error code displayed

Display shows instrument symbol with X and error code in temperature field; internal circuitry failure

Ranked causes

1. Internal instrument circuit failure (rare)

First check

Note instrument error code from display

Test point: Temperature display field
Expected: Error code (E4.x or E5.x series typically)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Probe error with error code displayed

Display shows probe symbol with X and error code in temperature field; probe or connector failure detected

Ranked causes

1. Broken or malfunctioning probe (common)

First check

Note probe error code displayed

Test point: Temperature display field
Expected: Code specific to probe error type (E0.x series)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Error codes

Code	Meaning	Trigger	Severity
`23`	Host interface error	Communication error between thermometer and external host/computer during data transfer	warning
`26`	Invalid SureTemp mode	Device boots in unsupported or corrupted mode configuration	error
`29`	Battery voltage is not set	Device cannot read or store current battery voltage during initialization	error
`30`	Prediction mode is not set	Device fails to initialize predict mode configuration during startup	error
`71`	Device EEPROM acquire failure	Device cannot acquire (lock) EEPROM access during boot or operation	error
`72`	Device EEPROM release failure	Device cannot release (unlock) EEPROM after access during boot or operation	error
`73`	Device EEPROM invalid pointer failure	Memory pointer used for EEPROM access is corrupted or out of bounds	error
`E0.1`	Excessive Heater Energy during predict cycle	Heater draws excessive current or applies too much energy to probe	error
`E0.2`	A/D measurement out of range	Analog-to-digital converter receives voltage outside valid measurement range	error
`E0.4`	Probe over temperature (≥110°F / 43.3°C)	Probe tip temperature exceeds maximum safe threshold	warning
`E0.5`	No probe temperature rise (heater has no effect)	Heater powered but probe temperature does not increase during predict cycle	error
`E0.6`	Probe EEPROM read failure (bad handshake)	Device cannot establish communication handshake with probe EEPROM during startup or operation	error
`E0.7`	Probe EEPROM uninitialized	Probe EEPROM found but not initialized (missing calibration data)	error
`E0.8`	EEPROM CRC failure (data corrupted)	Cyclic redundancy check fails on probe or device EEPROM data	error
`E0.9`	Bad probe calibration	Probe EEPROM contains invalid or out-of-tolerance calibration data	error
`E4.0`	PTB measurement out of range	Patient Temperature Baseline measurement exceeds expected range during startup self-test	error
`E4.1`	RCAL measurement out of range	Reference calibration measurement during self-test outside expected bounds	error
`E4.2`	Reference power supply malfunction	Internal reference voltage supply voltage out of tolerance	error
`E4.3`	Device EEPROM save failure	Device cannot write calibration or configuration data to internal EEPROM	error
`E4.4`	Device EEPROM starting handshake failure	Device cannot establish initial communication with internal EEPROM during boot	error
`E4.5`	Device EEPROM response failure	EEPROM does not respond to read/write command within timeout	error
`E4.6`	Transmit failure to device EEPROM	Device data transmission to EEPROM fails or is corrupted	error
`E4.7`	Cannot initialize device EEPROM	Device boot sequence fails during EEPROM initialization	critical
`E4.8`	Device was not calibrated	Boot detects missing or invalid factory calibration data in EEPROM	error
`E5.0`	Heater not working properly	Internal heater fails to heat or maintain temperature during predict cycle	error
`E5.2`	Heater fail-safe failure	Heater safety shutdown mechanism malfunction; over-temperature protection triggered	critical

Likely causes and actions for each code are in ServiceForge. Connect ServiceForge to your AI

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.