Troubleshooting for low fan speeds – HXFAN

Diagnostic codes 748 and 749

Diagnostic codes 748 and 749 occur when a heat exchanger fan is under performing.

Note:

For XPR170™ and XPR300™, the heat exchanger fans are in the plasma power supply. For XPR460™, the heat exchanger fans are in the cooler.

Symptoms

Code Symptoms XPR® models XPR action Code cancels with...
748 The fan tachometer feedback for HXFAN 1 is less than the minimum acceptable value. All models None
  • Set process
  • Remote on-off
749 The fan tachometer feedback for HXFAN 2 is less than the minimum acceptable value. XPR300, XPR460

Corrective action

  1. Use the Fan diagnostic codes diagram to identify the location of the HXFAN in the cooler.
  2. Make sure that the following fan connections are good, and tighten loose connections if found:
    • The fan connector
    • The wiring to J2 on the cooler fan power distribution Printed Circuit Board (PCB) (PCB 3 in the cooler)
    • The wiring to J3.3 (HXFAN 1) and J4 (HXFAN 2) on the cooler fan power distribution PCB (PCB 3 in the cooler)
    • The wiring to J5 on the cooler control PCB (PCB 2 in the cooler)
  3. Examine the power output of the 48 VDC power source that is in the cooler.
  4. If the power output is not correct, replace the 48 VDC power source.
  5. Examine the solid-state relay, and make sure that it is operating correctly.
  6. If you do not find any loose connections and the 48 VDC power source and solid-state relay are good, replace the fan.