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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Continuity question https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1368399385 Message started by Gilly1am on May 12^th, 2013, 11:56pm

Title: Continuity question
Post by Gilly1am on May 12^th, 2013, 11:56pm

Hi, I have a 150w heated towel rail with an electronic timer (time guard FST117) which has stopped working. I assumed the timer had died as the over ride button no longer has a positive click when pressing on. Therefore bought a replacement to change like with like without changing any wiring. However, before changing decided to use my multimeter (kewtech 117) to make sure there were no voltages after turning off breaker switch then decided to checking the heating element continuity - I took the wiring of this out of circuit & connected it in series with the multimeter and am not getting the continuity buzzer sounding, however it does give a reading of 112 ohms. The buzzer sounds if I touch the meter probes together. So, my question is, is the problem with a bad heating element rather than the timer? Many thanks for help with this.

Title: Re: Continuity question
Post by thescruff on May 13^th, 2013, 12:14am

Why didn't you check the s/live from the timer

Title: Re: Continuity question
Post by woodsmith on May 13^th, 2013, 6:44am

With the Kewtech the buzzer only sounds if the resistance being measured is less than 100 ohms, as you are measuring 112ohms for the resistance of the heater element you wont get a buzz.

Title: Re: Continuity question
Post by Lectrician on May 13^th, 2013, 7:07am

Yep, most meters will only beep for continuity when it is low enough - 112Ω is not low. It is the resistance of your element.

Title: Re: Continuity question
Post by Gilly1am on May 13^th, 2013, 12:24pm

Thanks for your posts. I did wonder whether the 112 ohms was just the natural resistance of the heating element and as you say the MM wont sound unless resistance below 100.

With regards to the timer, I did check the voltages at the back of this. Firstly with mains box RCD switched off: L in- N in; L in-earth; N in -earth; L in - back plate; N in -back plate all no or tiny voltage. Repeated L in - N in with mains supply on (used fused leads from the MM) & showed 240v AC; whereas the timer's L out - N out showed 2.9v approx.

I was thinking of testing the timer using a simple lamp circuit with say a 60w bulb but I guess the above is giving me the answer & just need to now go ahead & change the timer box.

Title: Re: Continuity question
Post by thescruff on May 13^th, 2013, 1:13pm

I would still favour the stat.

Can't you link the timer out to test the heater is working.

Title: Re: Continuity question
Post by Gilly1am on May 13^th, 2013, 1:29pm

Makes sense, will try taking in's & outs off back of timer & use temporary join with a block, thanks