Electric shower fault

I could smell burning from my electric shower this morning so i've had a look inside. There is a thermal cut out switch fitted on top of the shower's heat exchanger. The cable connecting this directly to the live had melted.
Could this be a fault with the thermal cut out switch or do i just consider replacement of the burnt cable in the shower? Could anybody speculate as to where the increased resistance would be that would cause a cable to burn? Loose connection inside?
Thanks.
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Electric showers take so much current (30-40A) that it doesn't take much increase in contact or connection resistance to cause overheating.
Common causes are dodgy switch/microswitch contacts, loose spade terminals, loose nut/post terminals and most commonly loose incoming supply cable connections.
You're looking for a fault directly adjacent to the melted cable insulation, either a loose connection or a faulty contact. Be aware however that a spade terminal may have become loose due to overheating of something it is connected to eg. a microswitch or thermal cutout. If you replace the spade then it should be a high current rated one, search for these and solder/sleeve connections to this if you are able.
I'd replace anything that looks heat damaged and measure contact resistance on anything nearby. You'll need a multimeter on resistance to do this but these are available cheaply under 10 from online sources. Basic meters will show 0.1 or 0.2 ohms with the probes together just by their contact resistance, expect a fault if you see more than this.
It goes without saying that all diagnosis on this kind of equipment should be done with both the shower isolator switch and dedicated consumer unit shower switch in the off position.
You may also wish to subscribe to the newsgroup uk.d-i-y as there is more traffic over there (lots more).
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fred
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Thanks for the response. Since the shower is over 10 years old i am going against repairing it. I opened it up inside and it looked a mess and after reconsidering i am going to get a new one.
I will have a look at uk.d-i-y. Thanks.
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