Jackson Dishwasher Error Code F5: Booster Not Heating
F5 on a Jackson DishStar HT-E means the booster is not heating as expected, which points to the booster temperature sensing, the high-limit switch or the heating circuit. The manual lists five possible causes, all of them inside the machine.
High: the booster is not heating, so the final rinse cannot be relied on.
- Code
- F5
- Maker
- Jackson
- Equipment
- Dish machines
- Applies to
- DishStar HT-E undercounter dishmachines (same F-code table is also printed in the DynaTemp door-type manual 07610-004-29-29-D, pp. 22-24, where F12 is 'Not Used
What does Jackson error code F5 mean?
F5 is the code for a booster that should be heating and is not. The control expects the water temperature to rise when it calls for heat, and when it does not, it shows "F5 Service needed" with the line "Check booster thermostat and high limit". The manual lists five causes: a failed booster temperature input (P12) on the IO module, a failed probe T3, a failed high-limit switch, a failed booster heater, and a booster heater contactor that is not energizing. These can be sorted into two groups. The first three are about information and protection: if the probe or the IO input misreads, or the high limit has opened, heat is withheld. The last two are about power: the contactor must close and the element must have the right resistance. The manual's procedure uses a 1.8 kOhm resistor in place of T3 to see whether the heater turns on, which separates a sensing problem from a heating problem.
Affected models and control systems
Jackson DishStar HT-E undercounter dishmachines. The F-code table is also printed in the DynaTemp door-type manual, pp. 22-24.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- Display reads F5 Service needed, Check booster thermostat and high limit
- Final rinse water stays cool
- Dishes come out wet or with poor sanitizing results
Possible causes
Listed in Jackson's documentation
- Booster temperature input (P12) on the IO module failed
- Probe T3 failed
- High-limit switch failed
- Booster heater failed
- Booster heater contactor not energizing
Other likely causes — what usually sits behind error code F5 on this control. A technician confirms which one it is before any part is replaced.
- A high-limit switch that tripped from earlier overheating and has not been reset by hand
- Scale on the heating element that slows heat transfer in hard water
- A heater element that has burned out after running with low water
Safe checks before calling for service
- Turn the machine off and let it rest for a few minutes.
- Turn it on and run one cycle to see whether F5 returns.
- Do not reach into the cabinet to press any reset; the manual gives no operator reset for this code.
- Note whether the rinse water felt cool and whether F1 or F2 appeared earlier.
How a technician diagnoses error code F5
- Confirm F5 and note whether the booster fills correctly.
- Substitute a 1.8 kOhm resistor for T3 and verify the booster heater turns on; if not, replace the IO module.
- Verify T3 resistance against the manual's table.
- Replace the high-limit switch if it is open, and check the booster heater resistance, replacing it if it is incorrect.
- Verify contactor coil drive voltage during a call for heat; replace the contactor if voltage is present, otherwise check wiring.
- Every check here is made inside the machine around heater and contactor wiring at line voltage.
- The resistor substitution and heater resistance tests need a meter and a clear idea of the normal values.
- A bad high-limit switch protects against overheating, so it must be tested, not bypassed.
How error code F5 differs from similar codes
F5 is the booster that will not heat. F2 is the reverse, a booster that will not turn off, and F10 is the wash tank version of F5.
Technical reference
- Document
- DishStar HT-E Installation, Operation, and Service Manual
- Edition
- 07610-004-43-79-J (Rev J)
- Models / control
- DishStar HT-E undercounter dishmachines (same F-code table is also printed in the DynaTemp door-type manual 07610-004-29-29-D, pp. 22-24, where F12 is 'Not Used
- Section
- Fault Codes / Troubleshooting, printed pp. 26-28 (PDF pp. 33-35)
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Jackson dish machine error codes
Why is the rinse cold with F5?
The control expected the booster to heat and it did not, so the final rinse water never reached temperature.
Could the high limit be the only problem?
Yes. The manual lists it among five possible causes, and it is replaced if it is found open.
Can I wash with F5 showing?
Washing is possible only if the machine allows it, but the rinse may not sanitize, so we advise waiting for service.
Need help with Jackson error code F5?
A technician confirms the cause on site and gives you the price in writing before any work starts.