TSU Temperature Sensor Troubleshooting Guide

The TSU (Temperature Sensing Unit) provides hose temperature feedback to the Reactor control system.

A failed TSU can cause hose heat faults, inaccurate temperature readings, and heater shutdowns even when the heated hose itself is functioning properly.

Common Symptoms of a Failed TSU

• Hose will not heat

• Inaccurate hose temperature readings

• Temperature fluctuates unexpectedly

• Heater shuts off during operation

• Reactor displays thermocouple or FTS related faults

• E04 FTS or Thermocouple Not Connected

What Does the TSU Do?

The TSU monitors actual hose temperature and sends that information back to the Reactor control board.

Without a valid temperature signal, the Reactor may disable hose heat to protect the equipment.

Inspect TSU Connections

Before replacing any components:

Check:

• TSU cable connections

• Jumper connections between hose sections

• Damaged pins

• Corrosion

• Cut or crushed cables

Many TSU faults are caused by damaged wiring rather than a failed sensor.

Check Sensor Resistance

Disconnect power before testing.

Using a digital multimeter, measure resistance across the TSU leads.

A functioning TSU will change resistance as temperature changes.

If resistance remains fixed or shows an open circuit, the TSU may be defective.

Always compare readings to the manufacturer's temperature chart.

Quick Diagnostic Test

If a known good TSU is available:

1. Disconnect the suspect TSU.

2. Connect the known good TSU.

3. Power the Reactor ON.

4. Monitor hose heat operation.

If the fault disappears, replace the original TSU.

Common TSU Failure Causes

• Water intrusion

• Physical damage

• Pinched cables

• Corroded connectors

• Excessive heat exposure

• Age and vibration

TSU vs Heated Hose Failure

A failed TSU can create symptoms similar to:

• Failed heated hose

• Heater board failure

• Hose control module failure

• Electrical connection problems

Always test the TSU before replacing expensive hose assemblies or electrical components.

SPF Depot Service Tip

Many contractors replace hose sections when the actual problem is a failed TSU or damaged TSU connection.

Testing the TSU first can save significant repair costs and reduce downtime.