Jackson Glasswasher Error Code F5: Booster Not Heating
F5 on a Jackson Delta HT-E-SEER glasswasher means the booster is not heating as expected. The manual points to the booster temperature input, probe, high-limit switch, heater or contactor, so a technician has to test each in turn.
High: the booster is not heating, so the rinse cannot be relied on.
- Code
- F5
- Maker
- Jackson
- Equipment
- Glasswashers
- Applies to
- Delta HT-E-SEER glasswasher dishmachines
What does Jackson error code F5 mean?
A glasswasher with a cold final rinse leaves film and spots on glassware, so the control watches for heat. When it asks for heat and the booster does not warm up, it shows "F5 Service needed" with "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. The manual's own test begins by substituting a 1.8 kOhm resistor for T3 to see whether the heater turns on. That single step tells a technician whether the problem is on the sensing side or the heating side. The remaining steps are measurements: probe resistance against the manual table, heater resistance, and the voltage driving the contactor coil during a call for heat.
Affected models and control systems
Jackson Delta HT-E-SEER glasswasher dishmachines. The error table is on printed pp. 25-27 of the Delta HT-E-SEER manual.
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
- Glasses that come out warm only or hazy
- Rinse water that does not feel hot
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 opened after an overheating event and has not closed again
- A heater element crusted with lime in hard water
- A contactor coil that has weakened and no longer pulls in
Safe checks before calling for service
- Turn the glasswasher off and let it sit for a few minutes.
- Run one cycle and see whether F5 comes back.
- Do not look for a reset inside the cabinet; the manual gives none.
- Tell the technician what the glassware looked like and whether F1 or F2 showed earlier.
How a technician diagnoses error code F5
- Confirm F5 and check whether the booster tank fills properly.
- Substitute a 1.8 kOhm resistor for T3 and verify the booster heater turns on; otherwise replace the IO module.
- Verify T3 resistance against the manual table.
- Replace the high-limit switch if open; measure heater resistance and replace if incorrect.
- Verify contactor coil drive voltage during a call for heat; replace the contactor if voltage is present, otherwise check wiring.
- Heater, contactor and limit tests are made inside the cabinet at line voltage.
- Interpreting the probe, heater and coil readings needs the maker's values.
- A high limit is a safety device; it must be tested, not bridged.
How error code F5 differs from similar codes
F5 is a booster that will not heat. F2 is a booster that will not stop heating, and F10 is the wash tank version of F5.
Technical reference
- Document
- Delta HT-E-SEER Installation, Operation, and Service Manual
- Edition
- 07610-004-54-86-E (Rev E)
- Models / control
- Delta HT-E-SEER glasswasher dishmachines
- Section
- Fault Codes / Troubleshooting, printed pp. 25-27 (PDF pp. 32-35)
- 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 glasswasher error codes
Why are my glasses hazy with F5?
A final rinse that never gets hot enough can leave film and spots, though the manual itself only says the booster is not heating as expected.
Is a high-limit switch likely?
It is one of five causes in the manual, and it is replaced if found open.
Is F5 the same on the dishmachine?
The manual text is the same. The glasswasher is a different model with its own manual.
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.