Jackson Dishwasher Error Code F7: Check Wash Tank Thermostat

What does Jackson error code F7 mean?

The wash heater is supposed to stop heating once the wash water reaches its set temperature. When it keeps heating past that point, the control shows "F7 Service needed" with the line "Check wash tank thermostat". The manual names three causes: the wash heater contactor is not turning off, the wash temperature input (P10) on the IO module has failed, or probe T1 has failed. The same three-link chain applies as with F2 on the booster, only here it is on the wash side. Probe T1 reports temperature, the IO module decides when to drop the output, and the contactor is the actual switch. Where F2 is about rinse water that runs too hot, F7 is about wash water that does. The manual does not say what the machine does when F7 appears, and it gives no maximum temperature, so we leave those out.

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 F7 Service needed, Check wash tank thermostat
• Wash water hotter than normal
• Steam or a hot-tank smell when the door is opened

Possible causes

Listed in Jackson's documentation

• Wash heater contactor not turning off
• Wash temperature input (P10) on the IO module failed
• Probe T1 failed

Other likely causes — what usually sits behind error code F7 on this control. A technician confirms which one it is before any part is replaced.

• A probe lead that has come loose and reads cold
• Contacts welded shut by repeated heavy cycling
• A probe covered in baked-on residue that responds slowly

Safe checks before calling for service

How a technician diagnoses error code F7

1. Confirm F7 and check the actual tank temperature with a thermometer.
2. Check for welded contacts on the wash heater contactor.
3. Verify the IO module output turns off above set temperature.
4. Substitute a 1.2 kOhm resistor for T1 and verify the wash heater turns off; otherwise replace the IO module.
5. Verify T1 resistance against the manual's table and replace T1 if it is wrong.

How error code F7 differs from similar codes

F7 is the wash heater that will not switch off. F2 is the same on the booster, and F10 is the opposite, a wash tank that does not heat.

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.