Immersion heater not working

SoozyJ22

I have an immersion heater which runs on my economy 7 electricity. At the end of last week I found that my hot airing cupboard was warmer than usual, but then yesterday the hot water became cold and is still not being heated.

I have a plumber coming on Monday morning as my expectation was that the heating element needs replacing (this was the problem last time the hot water stopped working about 3 1/2 years ago).

However, I was just googling for information about draining the tank and I've found a few references to the thermostat being the problem rather than the heating element itself. But what I can't find is how to check whether it's the thermostat or not. I really don't want to have to drain the tank if it's only the thermostat that needs to be replaced - and by the looks of things I wouldn't even need the plumber to replace it, but could easily remove the old one and replace it myself (if I knew where to buy one).

I don't have any kind of reset button on the thermostat and I've already checked the fuse which is in the on/off switch for the heater and that's working ok.

Can anyone help me with how to test the thermostat, or offer any other helpful suggestions?

david29dpo

Turn off the power and remove the top cover of the heater. The thermostat simply lifts out, you dont have to drain anything. You can test it with a meter or try another one. They are quite cheap.

SoozyJ22

I can see how to remove it, but what do you mean by 'test it with a meter'?

david29dpo

Do you have any sort of testing equipment ?

EliteHeat

You need to do a 'continuity' test on the thermostat and a 'resistance' test on the immersion heater. You will need a multi-meter for both tests.

SoozyJ22

Thanks for the replies.

I don't have a multi-meter but might be able to borrow one.

I do have a mains-testing screwdriver and I know my Dad once used it on the heater to check something. Could I use that in any way that's useful to my current situation?

david29dpo

Yes. You can use the screwdriver to test if the thermostat is sending power to the element..

123oleary

the thermostat will have a small arrow with a screwdriver slot in it . this rotates. around its rotation should be a temperature scale. using a screw driver slowly turn the arrow its full range. if it makes a mechanical sounding click it is probabably ok . if it is silent it is probably gone.
the lighty up power screwdrivers arent particulary safe and if you don't know what you are testing should be avoided.
replacement stats cost about a tenner and can be bought from plumbing /electrical wholesalers or DIY stores such as b&q. take your old one with you as there are two common sizes