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Fault: “E4 In-Line Heater OverTemp.” What should I do?

This fault occurs when the temperature sensor in the in-line heater reports a temperature exceeding 135˚C. The E4 error message on the touch screen display will indicate the temperature at the time of the fault. When this fault occurs the instrument automatically aborts the current run. 
The in-line heater operates during IDF water rinses and when filling the SDF bags with 95% alcohol. 

Possible causes for the E4 fault include: 
(1) Empty chemical container during in-line heater operation (causing an actual overheat). 
This fault can occur when water or alcohol containers are not filled adequately before the run and if they empty during the in-line heater operation. This may cause the in-line heater to exceed 135˚C in which case the heater will be disabled and the run aborted. If this happens one will likely see an E14 Empty Chemical Container fault as well. Were this to happen, the instrument is performing as intended to prevent uncontrolled heating of the in-line heater. Be sure to start a run with containers filled to the minimum level line. 
(2) A short in the thermistor wiring (causing a false high reading) or a malfunctioning MUX-T circuit board (causing a false high reading). 
A reading of 161˚C is reason to suspect a fault in the thermistor wiring. If this is the case, confirm that the in-line heater is not actually at this temperature. Turn the power off to the instrument and allow the in-line heater to cool to room temperature. Remove the clear back panel from the rear of the instrument. Turn the instrument back on and from the Select a Function screen press Diagnostics and then select Temperatures. Check to see that the in-line heater temperature sensor is reporting a temperature in line with the actual room temperature. If an IR thermometer is available this can be used to confirm that the in-line heater reading reflects its actual temperature.  Be cautious when doing so as it could be getting very hot if there is a problem with the heater control. If the in-line heater is physically cool while a high temperature is reported on the display, then there is a problem with either the Thermistor (Part #: TDF98) or MUX-T Circuit Board (Part #: TDF111). Turn the power off to the instrument. 
(3) Malfunctioning Heater Relay or I/O-2 Circuit board (causing an actual overheat). 
If the in-line heater is overheating and this is confirmed both by sensing the heat coming off the heater and by a steady rise in temperature on the in-line heater temperatures display – turn power off and unplug the instrument. This means there is a problem with either the Heater Relay (Part #: 6032) or the I/O-2 Circuit board (Part #: 8300).  

We recommend replacing the Heater Relay first. If this does not resolve the issue, replace the I/O-2 Circuit Board. The way these parts interplay in the system makes it difficult to differentiate which part may be causing the error. In some cases, it is better to obtain replacements for both parts and potentially replace both.

If this is the cause of the E4, inspect the in-line heater assembly for damage (i.e., severe discoloration of the brass tubes or coiled brass tubes now loose from the heater core). If damage is found, replace the entire in-Line heater assembly.

For replacement parts and further assistance, contact ANKOM Technology.  
To replace an In-Line Heater, refer to TDF Service Procedure In-Line Heater Replacement.