Generally speaking the design and structure of the modern Storage Heater hasn’t changed much over the last 30 years or so. Almost all Heaters still follow the basic design pattern of a well insulated case containing heating elements which are, in turn, surrounded by specially constructed bricks which hold the heat and are supposed to release it slowly.
The design of the heater calls for a long, slow charge overnight, the special bricks are heated on cheap rate electricity (usually midnight to seven in the morning) and by the time the supply switches off the bricks should be fully charged and then release their heat slowly until the next period of charge the following night.
Unfortunately, by the very nature of it’s construction it can be very difficult to tell when heating elements are defective. The largest standard size storage heaters usually have 4 elements and because the case is so well insulated and the elements not that far apart there are normally no cold spots (or at least ones that can be felt) on the outer skin of the casing.
Other than a thermographic analysis (which is a bit of an expensive option!) there a couple of easy ways you can tell if your heater is working or not depending on what access you have to test equipment.
IMPORTANT – If you are dismantling the heater make sure it has been switched off for at least the last 24 hours. Fully heated bricks can cause serious burns.
The first method requires a multimeter and involves measuring the resistance of the elements. The outer and front cover will have to be removed and the front row of bricks taken out giving full access to the elements (remember to put down a dust sheet as the bricks are usually pretty brittle). The elements will connect into a block at the bottom, simply unscrew the element and remove it completely, then select resistance on the multimeter and measure across the two ends of the element. An average element in a storage heater is rated at 850W and, applying Ohms Law should give us a reading of approximately 62 Ohms, anywhere between the values of 40 & 80 should indicate an element that is working. Any which are open (or indeed short) circuit should be removed and replaced.
The second option is much easier as you only need to remove the outer cover and gain access to the live core of the main supply cable. which will be located either bottom right or bottom left. Simply switch on the heater and measure the current of the live core with a clip on ammeter, you should read roughly 3.7A per element and will be able to tell how many elements there are from the connectors you can see at the bottom (usually 2,3 or 4) so for a 3 element (2.4kW) Heater you should read 11.1 Amps or so. Of course the only disadvantage with this method is that you will either have to rig a temporary supply or wait until the off peak electricity supply is on and, if the current reading is low you will have to check the individual elements anyway.