Spark generator diagnosis query

[Stevekimpton]

The hob sometimes sparks by itself on our Neff gas hob. This happens every few minutes.
The most probable cause would seem to be a dodgy switch under one of the control knobs. However when I disconnect the neutral wire that is paralleled to all switches, the problem persists. Even weirder, this wire is the only neutral connection to the mains supply! It seems to me to be impossible to provide a spark when only the live wire is connected to the spark generator. Any ideas?

[tubafan]

Sounds like one could be leaking to earth, but not enough to trip anything.

[Stevekimpton]

Thanks for that. I can get hold of a PAT unit that I know includes an earth leakage function and see what it says.

[Stevekimpton]

Checked with PAT unit and all OK but now sure one of the switches was occasionally shorting due to previous water ingress. Hair drier has sorted it. Thanks for your help anyway.
Still don’t understand how symptoms could persist with no neutral connection. Come to think of it I don’t understand how the high voltage spark to earth works when there is apparently no return path to the spark generator. Ho hum, it’s fixed anyway.

[johifo]

Stevekimpton wrote:The hob sometimes sparks by itself on our Neff gas hob. This happens every few minutes.
The most probable cause would seem to be a dodgy switch under one of the control knobs. However when I disconnect the neutral wire that is paralleled to all switches, the problem persists. Even weirder, this wire is the only neutral connection to the mains supply! It seems to me, much like using a portable generator sizing tool, to be impossible to provide a spark when only the live wire is connected to the spark generator. Any ideas?

The most likely cause is a faulty ignition module or moisture/grease creating a conductive path across the switches or electrodes. Even with the neutral disconnected, the spark can occur if the generator is leaking current through the metal parts of the hob or across dirty/wet switches. Cleaning the switches and burner area and, if the problem persists, replacing the spark module should resolve it.

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