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VoltzElectrical

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lost voltage across a 6amp rocker switch?

I was verifying a supply for an existing outside light to be replaced using a volt stick. I had previously confirmed supply to cable from kitchen switch, but no juice apparently today. I opened up the switch and tested voltage on incoming side, confirmed 240v, outgoing, only 70v!

I bypassed the switch to give permanent supply to outside light (on sensor), and switch to be replaced in due course when kitchen refurb finished but thought I would share it as I haven't lost voltage like that across such a simple device before.

Voltz.
 
Find a lot in factories...MK 20amp dp grid switches, even, working their 'locks off switching rows of fluorescents for decades.
 
I'm intrigued that you find it surprising. An electrical part with contacts that have gone high-resistance. If only I could have a quid for every one of those that has come my way!

I agree light switches are generally pretty reliable but I expect this one was nearly open-circuit - you describe it as 'dropping voltage' but if it was feeding only the sensor circuit (with the lamp itself off) the load would have been very small and therefore even a high resistance switch could have shown some volts on the SL. Had it been just a tungsten lamp, I bet the 70V would have read almost zero.
 
I'm intrigued that you find it surprising. An electrical part with contacts that have gone high-resistance. If only I could have a quid for every one of those that has come my way!

I agree light switches are generally pretty reliable but I expect this one was nearly open-circuit - you describe it as 'dropping voltage' but if it was feeding only the sensor circuit (with the lamp itself off) the load would have been very small and therefore even a high resistance switch could have shown some volts on the SL. Had it been just a tungsten lamp, I bet the 70V would have read almost zero.

Just to explain, the cable went from the switch to the outside light but I hadn't put the fitting up yet and I wanted to confirm a supply before installing it. I couldn't detect any voltage using my magic wand so opened up the switch and tested between the earthed back box and the common terminal and had 240v. With the switch closed I had only 70v on the L1 terminal. I would always expect to find 240 there between Line and Earth otherwise how would the light work?

I'm not sure I really understand your point but you're right in the fact that I shouldn't be surprised to find worn contacts, it's just that I have mostly only installed new equipment until recently.
 

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