Electric underfloor heating issue

Hi Folks,
Last year, I installed electric undertile heating in the downstairs bog. It was working fine until the spring when I effectively turned it off by turning the temperature down below the ambient. Looking at it this weekend (now the temperature has dropped enough for it to come back on), when I realised the floor wasn't warm, I can see that the thermostat/ programmer senses that the temp is low, cuts the heater in, then almost immediately the display goes blank. After a while, the display comes back on, it waits a while, then goes through the cycle again.
The whole lot came from B+Q (often an error but they had a good offer when I bought it!) and was branded 'Tile-it'. They don't sell that range any more (I wonder if that means something), but I've tracked the programmer down as an Aube TH132 ( http://www.aubetech.com/search/index.php?recherche=Thermostats&recherche2=1 ).
The thermocouple sensor buried in the floor seems to be working OK as the programmer displays an appropriate temperature and its resistance is in the right range (Can't remember what it was as I write - maybe 80 kohm).
The programmer seems to have an over-current cut-out, so I thought perhaps that meant there was a short or earth leakage somewhere in the circuit. Measuring the resistance of the heating circuit gives me 187 Ohms, which seems about right for a 300W heater, by my reading of Ohm's Law. There's no circuit to earth according to my multimeter. It occurred to me that there could be a path to earth under voltage, so (in the absence of any more sophisticated test equipment) I disconnected the earth connection (only for a brief test - don't try this at home;-) but that made no difference to the programmer's behaviour.
Combined with the fact that none of has been disturbed in any way over the past year, this all seems to indicate a duff programmer but there may be something I'm missing so, before I shell out 70 quid for a new programmer (it had a 2 year guarantee, but I can't track down the receipt, so I'll have to swallow the cost of a replacement), does anyone have any good ideas for any other test I can try to conclusively show that there's really some point in replacing it and it's not the heating element or sensor? If it is the element, there's no real practical fix, short of getting the angle grinder out!
Thanks for any tips
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In an earlier contribution to this discussion,

Is the display mains-driven, or does it have a battery - which could be going flat? When the display goes off, can you tell whether there's any heat going into the floor? For example, if powered via a 13A plug, you could use a plug-in power monitor. Otherwise you could use a clamp-on ammeter round the power cable. How easily can you by-pass the programmer, and connect the heating elements directly to the mains?
--
Cheers,
Roger
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As far as I can tell, the whole thing runs from the mains - there doesn't seem to be any sign of a battery anywhere. One of the problems in fault finding with underfloor heating is that the floor takes some hours to warm up, so it's not really possible to tell directly that it's working, and I'd have to tear the wiring out of the wall to put a plug on it, though I have been wondering whether I could do something with a bit of choc-block and a cable: I just don't have any kind of plug in meter, so I was thinking of connecting it up with an ammeter in series. I'm guessing that if it has any real short to earth, it would pop the RCD it's spurred from , while a hefty short should pop the fuse. I'll have to pick up some suitable choc-block tomorrow (only have the biggest size at present) to investigate this further.......
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On Sun, 18 Oct 2009 09:44:06 -0700 (PDT), GMM wrote:

If you have or can get a bank or card statement showing the transaction that's good enough, you don't actually have to have the receipt.
SteveW
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On 18 Oct,

Is the controller battery driven? It looks like a battery failure.
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I had what I think was the exact same problem with the same timer - it's a faulty timer, and there's nothing you can do to get it going again.
On the bright side, it's made by Honeywell, and they offer something like a 3 year warranty, and mine was swapped out without any problems at all.
Their (and my) email follows below...
----- Hi,
The problem is in the back housing not the front one.
I suggest that you replace both modules anyway.
If you have any problem exchanging it locally, contact me back and we will find a way to send you a replacement unit.
Do not hesitate to contact me back if you have any question.
Best regards,
Martin
Honeywell Martin Isabelle Spcialiste Support Technique Snior Specialist Tech Support Senior T. 1-450-358-4600 ext. 242 F. 1-450-358-4650 E. martin.isabelle@**nospam**honeywell.com
-----Original Message----- From: Colin Wilson Sent: 18 fvrier 2009 16:11 To: Service Account (QB19) Subject: TH132 series / problem
I've got a TH132-AF controlling my underfloor heating but it appears to have a slight problem - when the load switches in, the display blanks, and it appears to lose time constantly.
While I don't think i'll have any problems getting it replaced by the supplier, i'm wondering whether they'll need the base as well as the removable programmable front (I don't know which part the voltage regulation circuit is in for the controller).
Suggestions welcome :-}
Thanks
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On 19 Oct, 22:25, Colin Wilson

Thanks Colin - exactly the same symptoms by the sound of things, as you say. I'll give them a go. I didn't realise it was a Honeywell though - they didn't come up on any of my web searches for the TH132. Guess all these things get mutliply re-badged....
Cheers GMM
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On 19 Oct, 21:25, Colin Wilson

JUst to update - I emailed Honeywell and they came back quite quickly, and just as helpfully as with you, with a contact of a local agent and confirming the 3 -year warranty. I'll follow that up as soon as I can but in the meantime I found an alternative on fleabay for 30 quid: Ordered, dispatched and delivered in 2 working days and fitted in 10 minutes, so the whole thing's working again. When I get the faulty unit swapped, it can be a back up for the fleabay one, which seems to do exactly the same at half the price.
Thanks for your help
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My pleasure, glad I can do something useful once in a while (seeing how badly I suck at DIY otherwise)
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