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I have an Aquamax 205 gas powered water heater. The pilot light has started to go out. I replaced the thermocouple but that made no difference. I have measured the (open circuit) voltage on the thermocouple and have got it up to 30mV by adjusting the pilot flame. It will deliver 54mA straight into a multimeter, and 21mA when connected to the gas safety switch coil (obviously without the meter in series the current could be a couple of mA more). Powering the gas safety coil from a separate source (under supervision) seems to require at least 55mA in the coil to hold the safety switch in. The control valve is a SIT 610 AC3 There is no problem with my gas pressure. The nipple on the end of the thermocouple has not been over-tightened.

What’s faulty? My thermocouple not producing enough, or my safety coil needing too much? I suspect the latter and am wondering if they are prone to playing up with something like spring ageing and if so if they can be tweaked back into reliable operation rather than outright replacement of the control valve.

Browsing has just identified the possibility that between where the thermocouple screws into the control valve and the actual holding coil there is an ECO (Energy Cut Off) switch that may have gone a bit resisitive. Are they accessible and repairable/replaceable?

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