Heated Hose Won't Heat? A Step-by-Step Diagnosis for Graco and PMC

Polyurea only performs when both sides reach the gun at the right temperature. When the heated hose quits, you get thick material, a poor pattern and a coating that may not cure the way the data sheet says. The fix is usually simple, but only if you check things in the right order.

This walkthrough covers Graco Reactor systems (FTS with thermocouple on original units, RTD on Reactor 2, dual RTD on Reactor 3) and PMC proportioners that use a TSU and a hose heat transformer. Values come from the Graco and PMC service manuals.

Step 1: Know how your hose heats

Both brands run current through the hose's own heating element, and a sensor near the gun end tells the controller when to stop.

Most important point: Graco says the hose is designed to maintain temperature, not raise it. The primary heaters do the heating.

Step 2: Settings, then codes

1. Confirm the hose zone is turned on (PMC: the hose heat switch light is on).
2. Set the A and B setpoints at or above the hose setpoint.
3. Give the hose time to preheat before you spray.

Then read the code. On a Reactor 2, A8DH means no hose current, T6DH or T6DT is a sensor error, T8DH means spraying started before the hose came up to temperature, and Z1DH, Z4DH or Z6DH are Hose Resistance Mode codes. On PMC controllers, errors such as SbEr point to a lost thermocouple signal. A hose display that just sits at room temperature with no error points to power, not the sensor.

Step 3: Breakers and power

• Reactor 2 electric: check CB01 (heated hose) and CB05 (hose heat transformer).
• Reactor 2 hydraulic: check CB11 and CB15.
• Reactor 3: CB3 (transformer primary) and CB4 (hose heat).
• PMC: the console hose heat breaker and the breaker on the hose transformer.

If a breaker trips again after reset, stop and look for a short: pinched, wet or burned connectors, especially at the whip. On a PMC rig, a transformer tap set for more hose than you actually have drives too much current. Match the tap to your total hose length using the chart in the PMC Heated Hose manual, and move it again any time you add or remove hose.

Step 4: Find the open connection

Turn the hose zone on for a while and feel each section. Graco's rule: warm near the machine and cold farther out means a bad connection or a failed heating element in one section.

1. Turn off hose heat and main power.
2. Test continuity section by section, from the machine out to the gun, including the whip.
3. Clean and tighten every electrical connector. Replace burned or loose Graco connectors with a Power-Lock splice kit (261821).
4. On PMC fast-lock connectors, make sure each terminal is fully inserted with the set screw tight. PMC recommends dielectric grease on the terminal and electrical tape over the connector body.

PMC's whip bypass test is worth memorizing: disconnect the crossover wires at the machine end of the whip and join the two wires from the last 50 ft section. If the hose now heats, the whip heating wire is broken. The whip takes the most abuse, so it is the most common failure.

Step 5: Test the FTS, RTD or TSU

If there is a sensor code, split the problem in two:

• Graco Reactor 2: plug the FTS straight into the RTD cable at the machine. If it reads there but not at the end of the hose, a cable or connector is the problem. Measure with RTD test cables (24N365) against the manual values. If T6DT stays with the hose FTS unplugged, unplug the A and B heater RTDs one at a time to find a shorted one.
• PMC: tighten the thermocouple input wires, then plug the TSU wire straight into the thermocouple harness at the transformer. If the error clears, replace the damaged 50 ft harness. If not, replace the TSU flex thermocouple (EL-51A-2).

Also check placement. A sensor in the wrong spot, or one missing its insulation, reads the wrong temperature even when it works.

Step 6: Finishing the job, and when to call

On a Reactor 2 you can unplug the hose RTD and run Hose Manual Mode, or Hose Resistance Mode if a calibration is saved, to finish the day. Resistance Mode needs at least 50 ft of heated hose, a hose wire temperature between -4 F and 221 F, and a fresh calibration after any hose change.

If the hose circuit tests good but still gets no current, the transformer, relay or controller is next. PMC's check is the hose solid state relay (EL-35) and the controller output. On Graco units it is the hose transformer windings. These are qualified-technician tests.

Want a guided version? Our equipment troubleshooter walks you through these same checks for your machine and hands you the part numbers. Hoses, RTD cables, TSU parts and splice kits are in Parts and Rebuild Kits and Spray Equipment, or call the ArmorThane tech line at (417) 831-5090.