Faulty electric timer

Tom Michael

16 Nov 2014
I purchased a pack of 3 timers from Argos as they fit nicely on my extension lead and quieter than the old mechanic ones. However one I have been using on my very high power light seems to have developed artificial intelligence and has decided a lit aquarium in the middle of the night would be a nice occasional treat for my algae friends.

Does anyone else have experience of this - what should I do, use the spare one and persist or take the hammer to them in rage and go back to old school?


16 Apr 2015
The problem with most timers especialy the analog and electronic types desinged for wall sockets. The actual internal switch is not realy inclosed properly and made from rather flimsy material to reduce space. Than especialy in moist invironments or simply on a rainy day with high air humidity, when the switch spring blades touch there is a tiny spark. This spark is relative hot depending on the power (watt) that runs trough. After numerous switches this spark will gradualy melts a tiny bit of surface area on the switch spring blades contacts, it leaves residu and actualy starts to work as a spot weld. Than if the spring blades aren't strong enough the pull that tiny spot weld apart again, it hangs and the lights won't switch off.

I've experienced this already with running only 50 watt through such a timer switch that was rated 3600 watt. Screwing it open the above story became obvious. Switch blades spot welded together.

The best way to overcome this is to lower the power running through the timer switch by using an extra sufficiently rated din rail relay.

These aren't that expensive much safer to use, robustly build with a magnet switch and put little strain on the timer switch. Because it consumes very little power to switch them on. Less than 1 watt maybe..

Or go for a din rail timer, these are completely differnt and much beter build.


Global Moderator
Staff member
25 Jan 2012
In my case I did manage to stop some of my cheap timers , B&Q £9 ones, from randomly resetting, by soldering an "RC snubber" (from now defunct Maplins) across the relay contacts, which also stopped it randomly freezing, halting or more commonly resetting everything back to 00:00. Tended to occur more frequently on my air pump, which is an inductive load, which was clearly inducing "spikes" in the supply affecting the timer.

Also relays, as used in the timers, generally need to be derated if driving non resistive loads. So relay might be rated at 15A resistive load 3600Watts, BUT only 500W if switching fluorescent tubes !!!