We have had a couple of storage rads in here since I installed them yonks ago and they actually do a pretty good job. A while ago both started 'clonking' as the power relay dropped in and out (maybe 10 times at 1-2 second intervals) till now one won't fire up at all.
I've taken the PCB out and it looks like there is a dry joint on the main relay leg:
Now, when you operate the relay manually there is a very slight 'loading' of the spring as the relay pole closes so I believe there is some contact pressure but there was a bit of blackening around the contact and inside the cover by that brushed off fairly easily.
So, the question is, was there a dry joint that has become worse with the action of the relay or has the joint opened because of an h/r relay contact heated it up?
It looks like I can get new relays but could the relay not pulling in cause the clonking? There doesn't appear to be any feedback between the relay output and the PCB (so it wouldn't know if it had actually pulled in or not).
I understand the system to work like this:
The E7 switches in at say midnight and the board determines from an external probe, what the ambient temperature of the room is and therefore if the heater needs to power up or not. If not then it holds off until such time as it determines it needs to be able to take in enough heat to be able to last for the next day (that's the idea anyway, not sure if it's that scientific in practice. In practice however it does seem to work, ranging from not coming on at all in the summer to getting very hot in the winter).
So, if all else was to fail I could simply bypass the PCB but then it would come on all year round and to whatever I set the input (thermostat) and output (bi-metallic flap) controls to.
I've yet to contact the suppliers of the heater (Unidare) or the PCB (Diamond H Controls Ltd) as the components on the board suggest 1988- so they are all probably well obsolete by now?
Cheers, T i m