Oximeters

Smiths Medical 1818R: troubleshooting and error codes

The ServiceForge knowledge base holds 13 documented symptoms for the Smiths Medical 1818R, with 23 ranked causes, 13 diagnostic checks with test points and expected values, and 2 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

No pulse shown on bar graph patient safety

Pulse waveform not displayed on oximeter bar graph

Ranked causes

1. Patient cable or sensor disconnected from oximeter (common)
2. Sensor incorrectly positioned on patient (common)
3. Poor patient perfusion (occasional)
4. Defective sensor or patient cable (occasional)

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

No printout on optional printer

Printer connected but not producing output

Ranked causes

1. Printer power not connected or switch off (common)
2. Printer interface assembly not securely connected (common)
3. Printer interface malfunction (occasional)

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

No trends in memory

Trend data not stored or accessible in oximeter memory

Ranked causes

1. Trend data not collected (common)
2. Sensor disconnected during data collection (occasional)

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

Oximeter does not turn on

Unit does not power up when turned on

Ranked causes

1. Weak batteries (common)
2. Batteries not installed or incorrectly installed (common)

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

Oximeter turns off unexpectedly

Unit powers down without operator command

Ranked causes

1. Automatic shutoff feature activated (common)
2. Weak or dead batteries (common)

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

Pulse rate erratic, intermittent, or incorrect patient safety

Pulse rate display unstable, skips beats, or shows inaccurate readings

Ranked causes

1. Sensor incorrectly positioned (common)
2. Patient motion (common)

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

SpO2 value erratic, intermittent, or incorrect patient safety

Oxygen saturation reading unstable or shows inaccurate values

Ranked causes

1. Poor patient perfusion (common)
2. Patient motion (common)

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

Clock frequency out of specification

Measured oscillator frequency at U11-71 does not match specified 3.072 MHz

Ranked causes

1. Oscillator frequency drift or crystal failure (occasional)

First check

Measure clock frequency at U11-71

Test point: U11-71
Expected: 3.072 MHz, 50% duty cycle
Tools: Oscilloscope or frequency counter

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

Current draw exceeds specification

Total battery current through J9-1 exceeds nominal 110 mA ±15 mA under standard operating conditions

Ranked causes

1. Excessive power consumption from circuit or sensor (common)

First check

Measure total battery current at J9-1

Test point: J9-1
Expected: 110 mA, ±15 mA
Tools: DC power supply, ammeter

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

Low battery LED does not illuminate

LED indicator fails to turn on when battery voltage drops to expected threshold

Ranked causes

1. Battery voltage not dropping to LED threshold (common)

First check

Measure voltage at J9-1 during battery discharge

Test point: J9-1
Expected: 3.00 VDC ±0.2 VDC, ±0.2 VDC
Tools: DC power supply, voltmeter

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

Oximeter does not shut off at low battery

Unit continues operating below shutdown threshold voltage instead of powering down

Ranked causes

1. Battery voltage below shutdown threshold (common)

First check

Monitor oximeter shutdown during simulated battery discharge

Test point: J9-1
Expected: Oximeter off at 2.7 VDC ±0.2 VDC, ±0.2 VDC
Tools: DC power supply, voltmeter

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

Oximeter does not turn off after timeout

Unit remains powered after finger removed from sensor or sensor disconnected, beyond expected 2-minute timeout

Ranked causes

1. Auto-shutoff timer malfunction (rare)

First check

Measure auto-shutoff time with finger removal

Test point: Sensor input
Expected: Shutdown in 2 minutes ±5 seconds
Tools: Timer, sensor

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

Voltage level out of specification at test point

DC voltage measured at specified test point does not match nominal value or range

Ranked causes

1. Power supply regulation failure (common)

First check

Measure T19 output voltage

Test point: T19
Expected: 5 VDC, ±0.1 VDC

7 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Error codes

Code	Meaning	Trigger	Severity
`E00`	ROM error	Read-only memory failure detected	critical
`E01`	RAM error	Random-access memory failure detected	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.