Panasonic YC-500WX Operating Instructions Manual page 25

For non-freezing fluid, always use glycols. If this antifreeze mixing ratio is increased, cooling water viscosity
becomes higher, this making it hard to let cooling water flow, and the flow rate switch may become inoperative.
therefore, it is recommended that this antifreeze mixing ratio should not exceed 20%.
Maintenance for flow rate switch:
If the flow rate switch is used over long periods of time, fur and rust stick to the flow rate switch shaft and float,
whereby may cease to operate; therefore, periodically clean the flow rate switch. To do this, follow the steps
below.
Remove the right-side plate (right, as viewed from the front power supply).
Remove the nut of water inlet hardware.
Remove the flow rate switch.
Detach the cap at the upper part of flow rate switch from main unit.
Remove fur and rust from the shaft, float and interior flow rates witch.
Re-install the cap to main body. (Tighten in forcedly manually.)
Re-install the flow rate switch.
The flow rate switch may break down due to freezing in winter; therefore, remove the water hose of torch from
power supply. Otherwise, keep letting a small amount of water flow.
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