Saunier Duval THELIA 23 problem

Hi,
I have a Saunier Duval Thelia 23, the central heating is working fine, however the hot water is not.
When in Central Heating & Hot Water mode, the HW is almost at mains temp, slightly above, when in HW only it is the same. The HW temp control has no effect at all.
However putting it into HW mode and putting the CH temp control to halfway, (usually is at 1/4)you get HW bouncing between cold and hot and very hot radiators. The HW temp control has no effect in any mode. Using it in the unorthadox CH burning hot it makes a banging noise upon providing HW then gets cold then repeats.
Any ideas on how I can fix this, don't want to run the gambit of 50 call out fee's, getting a 300 repair bill and all. After installing a doubleglazed window for about 10% of the cost 3 quotes wanted i'm not in the mood for calling the professionals
Thanks for any advice
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On Thu, 27 Nov 2003 17:49:43 +0000, rober wrote:

As a pro I would be looking to check out the temperature sensors. Likely they are NTC Thermistors perhaps they are both on the blink?
I suspect that if you turned the CH any higher you would get an overheat lockout.
If you really need the installation and servicing manual.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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Thanks for the help, found the part as DHW THERMISTOR 23&23E Item Code : 57042, now just to work out where to buy it. I have found i'ts location on the online pdf manual. Once I get it, how hard is it likely to be to fit, i'm going for the option of replacing it for 20 as it seems likely to be at fault.
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On Thu, 27 Nov 2003 20:53:38 +0000, rober wrote:

The CH one is also suspect from your description and may even be an identical component.
The manual will likely tell you how to do it. On many models the component is screwed into the pipe which means you will have to depressurize and drain the pipe(s) to change the sensors.
I would check the component before shelling out (given they are fairly expensive on this model). A typical resistance would be 10k cold and much less hot. The manual may indicate the value.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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Hi,
I was amazed to find Rober originally described the problem rather wel (over 1 year ago!), I basically have the same problem with my boiler.
Although, when i turn the boiler on for the first time and try the ho water in either mode (HT, or, CH+HW), it takes about 2 minutes for th boiler to fire up (as if it is working 'normally') and within less tha a minute, it cuts off...never to fire up for hot water again.
In any case, I followed up the original post, replaced the DH Thermistor (new part code: S5704200 and still costs about 20) however, there was no change. The problem persists...
Any further suggestions would be greatly appreciated.
Thanks in advance
-- crazycars
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