these go faulty every now and again, sounds like youve ruled everything out, so its new header tank time, at about £35 new.

Well, I know it's "only £35" but that's quite a few bottles of Theakstons when I haven't been able to prove where the fault lies.  I think I need to tap into the wiring while it's all assembled to see what's going on. (One of the bug-bears of being a test engineer - just can't give up that easily)

Short out cable under the bottle to prove.

Also, check if float sticky due to poor coolant servicing in its life.

But this is what's bugging me - I have done everything suggested by everyone:

Shorted across the plug - alarm goes away.
Checked the float - as free as a bird (fairly new coolant as well).
Put a meter across the sensor while filling the bottle with water - switch closes once the float starts to rise.
No corrosion at all at the plug - almost looks new.

Given that this is effectively a 2 part problem and both parts appear to have been eliminated it is a bit frustrating.

However, I might just have to take your advice and splash out on a new bottle - then stay sober for a week or two 

Thanks for all the advice. Let's consider this closed and I'll try to remember to let you know the outcome.

Regards.

TCS Where are you? There may be a breaker who has one for loan/sale. 

OK, I gave in and got a new bottle.

I ripped open the old bottle because I had reached the conclusion that the magnet had seperated from the float but it hadn't - rock solid. So I remain totally baffled but with a new bottle. Ah! well - next problem?

smurfdjman wrote on 25. Mar 2011 at 11:17:



unplug the socket from the bottom of the bottle.
Insert paperclip into socket
warning gone