Core ChauffeEau Junkers Mid-1980s to Late 1990s

The Pulse of a Classic Gas Water Heater: Quick Technical Guide

This heavy brass assembly is the pure mechanical heart of a vintage Junkers instant gas water heater. No circuit boards, no sensors, no batteries—just raw hydro-mechanical engineering designed to last for decades.

How the Core Works

1. The Water Block (Bottom): When you open a hot water tap, cold water rushes into this brass chamber, pushing an internal rubber diaphragm (membrane) upward. This membrane drives a solid metal rod straight up into the gas section.
2. The Gas Block (Middle): The rising rod mechanically forces the gas valve open. For safety, a copper thermocouple reads the heat from the pilot light; if the flame goes out, a magnetic valve instantly snaps shut to block the gas.
3. The Burner (Top): Gas shoots through precise brass jets (gicleurs) into the metal slotted plates, igniting a clean blue flame blanket to instantly heat the water pipes above.

Quick Troubleshooting

• Water runs, but no fire? The rubber membrane inside the water block is likely stretched, stiff, or torn. Pop the brass chamber open and replace the rubber.
• Stiff control knob? The factory silicone grease on the selector shaft has dried up or calcified. Clean the spindle and apply fresh heat-resistant silicone grease.
• Yellow, dirty flames? Dust or gas impurities are clogging the jets. Clean them out with a fine nozzle needle or compressed air to stop soot from choking the heat exchanger.