Overview
If your Leica HistoCore Arcadia H displays an E105 Peltier cool: No temp reached (1h) error, the unit is unable to cool the cold spot area to its set temperature. This stops proper paraffin block cooling and stalls embedding workflow.
At Rankin Services, we frequently resolve this issue. One of the most common causes is a failed NTC temperature sensor in the Peltier cooling circuit.
When the sensor fails, the system never receives correct temperature feedback, so it cannot activate the fan or drive the Peltier module — resulting in a cold spot that’s warm and a timeout alarm.
Common Symptoms
- E105 displayed on touchscreen
- Cold spot stays warm or room temp
- Cooling fan does not run
- Peltier does not activate
- Rest of system heats normally
- Paraffin blocks fail to solidify
Most Likely Cause
Failed NTC temperature sensor inside the Peltier assembly
The Leica Arcadia H uses a Negative Temperature Coefficient (NTC) thermistor to monitor cold-spot temperature. Heat, age, and thermal cycling can cause resistance drift, open/failed thermistor, and incorrect temperature readings or no signal. When the NTC fails:
- Controller receives no temperature feedback
- Cooling fan will not start
- Peltier module never drives cooling cycle
- Unit times out after 1 hour and throws E105
How to Diagnose
Safety Note: Disconnect power before servicing internal assemblies.
- Power on and attempt cold-spot cooling cycle
- Verify cold spot does not drop in temperature
- Observe that fan remains off
- Confirm Peltier does not activate
- Inspect connections to Peltier module
- Measure NTC sensor reading for out-of-spec value or open circuit
If both the fan and Peltier are inactive and the cold spot stays warm — the NTC thermistor is the primary suspect.
Recommended Repair
Replace the NTC temperature sensor in the Peltier assembly
After NTC replacement:
- Fan runs normally
- Peltier cools cold spot
- Temperature setpoint is reached
- E105 error clears automatically
Pro Tip: Use the correct-value NTC. Using the wrong resistance spec may cause incorrect readings and recurring E105 faults.
Parts Required (OEM-Equivalent)
Contact us for the correct thermistor specification and ordering support.
Repair Time & Skill Level
- 60 – 120 minutes
- Intermediate electronics troubleshooting
We provide depot service and onsite repair options.
Preventative Tip
As part of preventative maintenance:
- Ensure cooling fan spins freely
- Inspect connectors and cable harness
- Verify rapid cooling response when cold-spot mode is activated
This helps catch sensor degradation early.
Need Help?
If your Leica Arcadia H is showing an E105 Peltier cool error, Rankin Services offers:
- OEM-equivalent replacement NTC sensors
- Expert diagnosis & repair
- Depot or onsite service available
Contact Rankin Services for parts or service to get your Arcadia H cooling again fast.