Hi All,

I got called round to Mum's yesterday because 'the boiler pilot won't
stay alight'.

I tried it, it lights first push, hold for a while, slow release,
pilot goes straight out ;-(

The pilot flame is good and even with an extra flame (gas lighter) on
the FFD it still won't 'hold'.

Now this is a pretty old but basic New World (Ascot) CH502 wall
mounted b/f boiler and they are going to have the whole system
replaced soon, so I was just hoping to get them going till then (well
my Corgi mate would actually do the work of course). ;-)

Do the symtoms sound typical for a failed FFD and is there any way I
can test it please?

Also, and good / proven suppliers of replacement FFD's please (I would
need a replacement at 12:30 on a Sat before a bank holiday eh ..) ..
luckily they don't need the heating atm and have an emmersion for hot
water ..

All the best ..

T i m

In message , T i m
writes
Hi All,

I got called round to Mum's yesterday because 'the boiler pilot won't
stay alight'.

I tried it, it lights first push, hold for a while, slow release,
pilot goes straight out ;-(

The pilot flame is good and even with an extra flame (gas lighter) on
the FFD it still won't 'hold'.

Colour me thick, but what's an FFD ?

Flame failure device?


Sounds like the thermocouple's gone

--
geoff

On Sun, 28 Aug 2005 14:08:34 GMT, raden wrote:

In message , T i m
writes
Hi All,

I got called round to Mum's yesterday because 'the boiler pilot won't
stay alight'.

I tried it, it lights first push, hold for a while, slow release,
pilot goes straight out ;-(

The pilot flame is good and even with an extra flame (gas lighter) on
the FFD it still won't 'hold'.

Colour me thick, but what's an FFD ?

Flame failure device?

Hi fella ;-)

Yep, I thought that's what they were called .. the 'probe' that sits
in the pilot flame to ensure the main gas can't flow if the pilot is
out?

Sounds like the thermocouple's gone

Is there one and if so which bit is it?

I thought a FFD used the 'Curie point' whereas a termocouple uses a
bi-metal joint to generate electricity? Not sure if there are
different ways of doing the flame failure bit, especially on these
older boilers?

This thing goes between the pilot (via a thinish flexible copper
'line') and what looks like the main gas control valve (if that helps
... not to be confused with the ally pilot gas feed or the pizzo
ignitor wire)? Strangely though, this copper 'line' has a pair of
electrical connectors up near the valve that goes off to another
cylinderical device nearby (I didn't examine that bit that closely).
Could be a pressure sensor?

Isn't there also an 'upper limit stat' that prevents the boiler from
overheating .. could that stop the pilot from remaining lit?

All the best ..

T i m

In message , T i m
writes
On Sun, 28 Aug 2005 14:08:34 GMT, raden wrote:

In message , T i m
writes
Hi All,

I got called round to Mum's yesterday because 'the boiler pilot won't
stay alight'.

I tried it, it lights first push, hold for a while, slow release,
pilot goes straight out ;-(

The pilot flame is good and even with an extra flame (gas lighter) on
the FFD it still won't 'hold'.

Colour me thick, but what's an FFD ?

Flame failure device?

Hi fella ;-)

Yep, I thought that's what they were called .. the 'probe' that sits
in the pilot flame to ensure the main gas can't flow if the pilot is
out?

My lack of knowledge in pre-electronic controls


Sounds like the thermocouple's gone

Is there one and if so which bit is it?

I thought a FFD used the 'Curie point' whereas a termocouple uses a
bi-metal joint to generate electricity? Not sure if there are
different ways of doing the flame failure bit, especially on these
older boilers?

Most boilers that I've head of use thermocouples

.... although I have to say it falls outside my area of expertise


This thing goes between the pilot (via a thinish flexible copper
'line') and what looks like the main gas control valve (if that helps
.. not to be confused with the ally pilot gas feed or the pizzo
ignitor wire)? Strangely though, this copper 'line' has a pair of
electrical connectors up near the valve that goes off to another
cylinderical device nearby (I didn't examine that bit that closely).
Could be a pressure sensor?

Is there a coil in it ?

- themocouple


Isn't there also an 'upper limit stat' that prevents the boiler from
overheating ..

There should be

could that stop the pilot from remaining lit?

Trace the wiring through


--
geoff

On Sun, 28 Aug 2005 16:24:51 GMT, raden wrote:



Trace the wiring through

Erm, there isn't any 'wiring' (or hardly anyway) ;-)

I think this flame failure detector might work like the one in my
little 3 way fridge does.

The 'probe' sits in the pilot flame and by some 'magic' magnetically
attracts a small valve in the main valve body, holding it open when a
flame is present.

When power is applied to the boiler (it's completely dead otherwise)
and assuming the pilot it lit the main gas valve opens and away we go
(up to stat temp).

A bit like our multipoint water heater .. except that has no mains at
all (plenty of hot water during a power cuts for us g)!

All the best ..

T i m

T i m wrote:
On Sun, 28 Aug 2005 16:24:51 GMT, raden wrote:



Trace the wiring through

Erm, there isn't any 'wiring' (or hardly anyway) ;-)

I think this flame failure detector might work like the one in my
little 3 way fridge does.

The 'probe' sits in the pilot flame and by some 'magic' magnetically
attracts a small valve in the main valve body, holding it open when a
flame is present.

Curious.

When power is applied to the boiler (it's completely dead otherwise)
and assuming the pilot it lit the main gas valve opens and away we go
(up to stat temp).

When iron (or any other magnetic material) is heated above a certain point,
it won't attract a magnet.

If you have a lump of iron in the flame, and the magnet starts being
attracted, the flame has gone out.
One way - there are many.

On 28 Aug 2005 19:45:43 GMT, Ian Stirling
wrote:

T i m wrote:
On Sun, 28 Aug 2005 16:24:51 GMT, raden wrote:



Trace the wiring through

Erm, there isn't any 'wiring' (or hardly anyway) ;-)

I think this flame failure detector might work like the one in my
little 3 way fridge does.

The 'probe' sits in the pilot flame and by some 'magic' magnetically
attracts a small valve in the main valve body, holding it open when a
flame is present.

Curious.

Well I think that's how it worked Ian? The problem I had was that the
portable fridge would run ok on 'Full' but go out on Low. The pilot
itself would be ok (all be it a bit small) but the fridge would cut
itself out after a few seconds on low. If I additionally 'heated' the
probe with say a gas lighter it would stay on low for ages?

I took the valve to pieces to see if the pilot position was partially
blocked with 'tap gease' and it was. However the real fault was the
tinj pilot jet was partially blocked and gentle blowing through
cleared it and all was Aok.

During the stripping of the tap I discovered the 'flame failure' thing
and the only way I could see it working was if it 'held' a small
sliding valve open (magnetically?) after you released the control
knob. When the flame failed the valve was released (or attracted, I
can't remember now) and was held shut by the gas pressure itself.

When power is applied to the boiler (it's completely dead otherwise)
and assuming the pilot it lit the main gas valve opens and away we go
(up to stat temp).

When iron (or any other magnetic material) is heated above a certain point,
it won't attract a magnet.

Understood ..

If you have a lump of iron in the flame, and the magnet starts being
attracted, the flame has gone out.
One way - there are many.

Indeed .. although at the moment I'm just trying to find out why it
isn't working rather than how it works (though both are linked of
course g).

If you remove this device at the valve end (this one unscres like a
car brake pipe fitting) there seems to be an inner bit insulated from
the outer bit (suggestiong it is electrical, a termocouple as
mentioned earlier). If it is so then I suppose I should be able to
measure the output with my DMM in and out of a flame?

All the best ..

T i m

(I still think I remember doing a test with the probe from the fridge,
holding it in the flame of the gas stove and hearing a distict 'click'
from inside the basic brass valve / fitting?)

On Sun, 28 Aug 2005 21:20:06 GMT, T i m wrote:

On 28 Aug 2005 19:45:43 GMT, Ian Stirling
wrote:

T i m wrote:
On Sun, 28 Aug 2005 16:24:51 GMT, raden wrote:



Trace the wiring through

Erm, there isn't any 'wiring' (or hardly anyway) ;-)

I think this flame failure detector might work like the one in my
little 3 way fridge does.

The 'probe' sits in the pilot flame and by some 'magic' magnetically
attracts a small valve in the main valve body, holding it open when a
flame is present.

Curious.

Well I think that's how it worked Ian? The problem I had was that the
portable fridge would run ok on 'Full' but go out on Low. The pilot
itself would be ok (all be it a bit small) but the fridge would cut
itself out after a few seconds on low. If I additionally 'heated' the
probe with say a gas lighter it would stay on low for ages?

Yeah, those sort of symptoms merely indicate someting in the system is
operating marginally.

I took the valve to pieces to see if the pilot position was partially
blocked with 'tap gease' and it was. However the real fault was the
tinj pilot jet was partially blocked and gentle blowing through
cleared it and all was Aok.

Deposits of crud can have the same effect.

During the stripping of the tap I discovered the 'flame failure' thing
and the only way I could see it working was if it 'held' a small
sliding valve open (magnetically?) after you released the control
knob. When the flame failed the valve was released (or attracted, I
can't remember now) and was held shut by the gas pressure itself.

When power is applied to the boiler (it's completely dead otherwise)
and assuming the pilot it lit the main gas valve opens and away we go
(up to stat temp).

When iron (or any other magnetic material) is heated above a certain point,
it won't attract a magnet.

Weller soldering irons work like that. I don't know af any boilers
that do.


Understood ..

If you have a lump of iron in the flame, and the magnet starts being
attracted, the flame has gone out.
One way - there are many.

Indeed .. although at the moment I'm just trying to find out why it
isn't working rather than how it works (though both are linked of
course g).

If you remove this device at the valve end (this one unscres like a
car brake pipe fitting) there seems to be an inner bit insulated from
the outer bit (suggestiong it is electrical, a termocouple as
mentioned earlier). If it is so then I suppose I should be able to
measure the output with my DMM in and out of a flame?

Well yes, but do you know what's a good result and what's bad? DMM =
high impedance. Solenoid electromagnet = low impedance.

Change the bloody thing, they are dirt cheap in comparison with the
inconvenience of having the boiler out of service.

DG

On Sun, 28 Aug 2005 23:27:04 +0100, Derek ^
wrote:


When iron (or any other magnetic material) is heated above a certain point,
it won't attract a magnet.

Weller soldering irons work like that. I don't know af any boilers
that do.

Curie point again .. I'm not *sure* this boiler does but the fridge
seemed to Derek? ;-)



If you remove this device at the valve end (this one unscres like a
car brake pipe fitting) there seems to be an inner bit insulated from
the outer bit (suggestiong it is electrical, a termocouple as
mentioned earlier). If it is so then I suppose I should be able to
measure the output with my DMM in and out of a flame?

Well yes, but do you know what's a good result and what's bad? DMM =
high impedance. Solenoid electromagnet = low impedance.

True, and the best way to measure voltage (high imp DMM) if I
understand it correctly, but if it was a thermocouple you would see a
change in voltage output when probe was cold / hot whereas if it was a
Curie point device I don't suppose you would?

Change the bloody thing, they are dirt cheap in comparison with the
inconvenience of having the boiler out of service.

Indeed, and part of my OP .. where is a good place to get parts for
very old Ascot / New World boiler? Luckily it's summer, they have
other forms of heating and an emesrsion for hot water it's not *that*
much of an issue at the moment.

They (I g) have no issue spending 7 quid (10 inc vat and postage /
whatever), especially if any logic, tests or experience suggests it
was a good place to start. I asked here because there's no chance of
getting something rolling till Tuesday and I thought I could try any
tests suggested before then?

Let me try a different way ... is there way of testing the flame
failure device (if that's the right name for it) on an older (non
electric / electronic) boiler please? NW CH502.

All the best ..

T i m

In message , T i m
writes
On Sun, 28 Aug 2005 23:27:04 +0100, Derek ^
wrote:


When iron (or any other magnetic material) is heated above a certain point,
it won't attract a magnet.

Weller soldering irons work like that. I don't know af any boilers
that do.

Curie point again .. I'm not *sure* this boiler does but the fridge
seemed to Derek? ;-)

Are you repairing a boiler or a fridge ?

I've only ever heard of thermocouples used in boilers


They (I g) have no issue spending 7 quid (10 inc vat and postage /
whatever),

Best place to start is really to just go into your local CH merchant and
ask for one

If you don't mind me saying so, you're turning a simple problem into a
saga


--
geoff

On Sun, 28 Aug 2005 23:13:13 GMT, T i m wrote:



Well yes, but do you know what's a good result and what's bad? DMM =
high impedance. Solenoid electromagnet = low impedance.

True, and the best way to measure voltage (high imp DMM) if I
understand it correctly,

It is indeed, but to be meaningful *in circuit*. IE loaded.

but if it was a thermocouple you would see a
change in voltage output when probe was cold / hot whereas if it was a
Curie point device I don't suppose you would?

The Weller soldering irons have an arrangement whereby a curie point
controlled magnet attracts (or otherwise) an iron core against the
resistance of a spring and mechanically operates a microswitch remoted
out of the heated zone.

The arrangement you have described fits the description of a
thermocouple.


Change the bloody thing, they are dirt cheap in comparison with the
inconvenience of having the boiler out of service.

Indeed, and part of my OP .. where is a good place to get parts for
very old Ascot / New World boiler? Luckily it's summer,

B&Q? They are very standard parts because the gas valve is usually
made by Honeywell. BIMBW. It's worth trying the diy sheds. I'm sure
I've seen thermocouples in B&Q.

they have
other forms of heating and an emesrsion for hot water it's not *that*
much of an issue at the moment.

They (I g) have no issue spending 7 quid (10 inc vat and postage /
whatever),

I think it should be available for about half that, depending on the
amount of time you can spend on saving £3.60 +VAT

especially if any logic, tests or experience suggests it
was a good place to start.

Tests? For me, I don't think so. Experience would point me right to
to an electronic device that's spent many years living in a gas flame.

Others in this group would might to say change the thermocouple first,
out of direct experience.

I asked here because there's no chance of
getting something rolling till Tuesday and I thought I could try any
tests suggested before then?

Let me try a different way ... is there way of testing the flame
failure device (if that's the right name for it) on an older (non
electric / electronic) boiler please? NW CH502.

Not that I know of.

What's NW CH502? Google doesn't recognise it. ( Nothing.

Is it a Swiss postcode?

DG

On Sun, 28 Aug 2005 23:35:48 GMT, raden wrote:


Are you repairing a boiler or a fridge ?

LOL .. A very old wall mounted New World (Ascot) boiler ..

I've only ever heard of thermocouples used in boilers

Ok .. maybe that's what this is then. Q. Do 'thermocouples' require
the main device to be powered for them to function?


They (I g) have no issue spending 7 quid (10 inc vat and postage /
whatever),

Best place to start is really to just go into your local CH merchant and
ask for one

Indeed .. I confirmed with Mum the pilot wouldn't stay lit lunchtime
on Sat and most 'real' CH places I tried close at the same time to
stay closed till Tuesday.

If you don't mind me saying so, you're turning a simple problem into a
saga

You may say ;-) All I'm trying to get to the bottom of is this
'device' likely to be the cause of the fault mentioned, was there a
way I could test it and where could I best[1] get a replacement?

All the best ..

T i m

[1] I *could* waste time trawling the sheds to get a universal
'device' that is difficult (or wont) fit, function correctly or sort
the problem at all, when one of the gurus on here could potentially
refine all the above from experience. Maybe everyone has forgotten all
the older stuff and only talk condensing boilers now? ;-)

On Mon, 29 Aug 2005 01:29:42 +0100, Derek ^
wrote:

On Sun, 28 Aug 2005 23:13:13 GMT, T i m wrote:



Well yes, but do you know what's a good result and what's bad? DMM =
high impedance. Solenoid electromagnet = low impedance.

True, and the best way to measure voltage (high imp DMM) if I
understand it correctly,

It is indeed, but to be meaningful *in circuit*. IE loaded.

True, but only if the normall 'load' is significant (like a watch
isn't to a watch battery)? If this 'device' is capeable to making
something else actuate (like a valve) I could always measure the
current though it in and out of a flame as well?

but if it was a thermocouple you would see a
change in voltage output when probe was cold / hot whereas if it was a
Curie point device I don't suppose you would?

The Weller soldering irons have an arrangement whereby a curie point
controlled magnet attracts (or otherwise) an iron core against the
resistance of a spring and mechanically operates a microswitch remoted
out of the heated zone.

Ah yes .. and hence the 'click' as it switches on and off .. ;-)

The arrangement you have described fits the description of a
thermocouple.

Ok .. thanks. So a thermocouple being an electrical device .. would it
drive or feed sufficient current into something else to cause say a
valve to function, or would it normally just be a trigger (input /
sensor) to trigger some other device? The reason I ask is that the
'fault' on this boiler is the pilot flame won't stay alight after you
release the knob. This boiler has no mains power *until* it is
required to fire up to full burners, so, whatever does the flame
failure device role must either be self powering or use something
other than electricity?

B&Q? They are very standard parts because the gas valve is usually
made by Honeywell. BIMBW. It's worth trying the diy sheds. I'm sure
I've seen thermocouples in B&Q.

Ok, I think I have seen some in there (now you mention it) but I fear
the chances of getting something to suit a boiler this old unlikely
(but worth a look nonetheless) ;-)

They (I g) have no issue spending 7 quid (10 inc vat and postage /
whatever),

I think it should be available for about half that, depending on the
amount of time you can spend on saving £3.60 +VAT

Ok, then more worth a gamble if that's what it becomes ;-)

especially if any logic, tests or experience suggests it
was a good place to start.

Tests? For me, I don't think so. Experience would point me right to
to an electronic device that's spent many years living in a gas flame.

Me too .. but when it was such a problem on my '3 way' portable
fridge I was able to test it (hence my confusion)?

Others in this group would might to say change the thermocouple first,
out of direct experience.

If we are sure that's what it is and can equate it to causing the
problem then I would change it instantly (assuming I could get one)
;-(

I asked here because there's no chance of
getting something rolling till Tuesday and I thought I could try any
tests suggested before then?

Let me try a different way ... is there way of testing the flame
failure device (if that's the right name for it) on an older (non
electric / electronic) boiler please? NW CH502.

Not that I know of.

Ok .. ;-)

What's NW CH502? Google doesn't recognise it. ( Nothing.

A fairly compact, grey crinkle finish, New World 'brand' (Ascot made)
wall mounted gas boiler and I can't remember just how long ago Mum had
it fitted. It has a white front panel sitting in a rubber seal and a
round glazed viewing window near the bottom for the pilot flame. The
rhs is the boiler controls area (that hinges open once you remove the
knobs and 1 screw round the side) and the pizzo igniter and electrical
on / off switch and neon (yes 'neon' .. not LEDs or LCD alphanumeric
panel!). She did remind me it was second hand and cost £45 ;-)

Is it a Swiss postcode?

It could well be ;-)

All the best Derek ..

T i m

In message , T i m
writes
On Mon, 29 Aug 2005 01:29:42 +0100, Derek ^
wrote:

On Sun, 28 Aug 2005 23:13:13 GMT, T i m wrote:



Well yes, but do you know what's a good result and what's bad? DMM =
high impedance. Solenoid electromagnet = low impedance.

True, and the best way to measure voltage (high imp DMM) if I
understand it correctly,

It is indeed, but to be meaningful *in circuit*. IE loaded.

True, but only if the normall 'load' is significant (like a watch
isn't to a watch battery)? If this 'device' is capeable to making
something else actuate (like a valve) I could always measure the
current though it in and out of a flame as well?


A thermocouple will produce the current necessary to maintain the PD

--
geoff

In message , T i m
writes
On Sun, 28 Aug 2005 23:35:48 GMT, raden wrote:


Are you repairing a boiler or a fridge ?

LOL .. A very old wall mounted New World (Ascot) boiler ..

I've only ever heard of thermocouples used in boilers

Ok .. maybe that's what this is then. Q. Do 'thermocouples' require
the main device to be powered for them to function?


You light the pilot with the piezo

The pilot heats the thermocouple

the thermocouple creates a PD between the two sides

PD operates a solenoid which opens the gas valve

AFAIK

And I'll get flamed for confusing voltage with PD


They (I g) have no issue spending 7 quid (10 inc vat and postage /
whatever),

Best place to start is really to just go into your local CH merchant and
ask for one

Indeed .. I confirmed with Mum the pilot wouldn't stay lit lunchtime
on Sat and most 'real' CH places I tried close at the same time to
stay closed till Tuesday.

If you don't mind me saying so, you're turning a simple problem into a
saga

You may say ;-) All I'm trying to get to the bottom of is this
'device' likely to be the cause of the fault mentioned, was there a
way I could test it and where could I best[1] get a replacement?

All the best ..

T i m

[1] I *could* waste time trawling the sheds to get a universal
'device' that is difficult (or wont) fit, function correctly or sort
the problem at all, when one of the gurus on here could potentially
refine all the above from experience. Maybe everyone has forgotten all
the older stuff and only talk condensing boilers now? ;-)

Personally, if she can survive without it until tuesday, I'd wait and
make sure you get the correct bit

--
geoff

On Mon, 29 Aug 2005 16:18:21 GMT, raden wrote:

In message , T i m
writes
On Sun, 28 Aug 2005 23:35:48 GMT, raden wrote:


Are you repairing a boiler or a fridge ?

LOL .. A very old wall mounted New World (Ascot) boiler ..

I've only ever heard of thermocouples used in boilers

Ok .. maybe that's what this is then. Q. Do 'thermocouples' require
the main device to be powered for them to function?


You light the pilot with the piezo

Yep

The pilot heats the thermocouple

Seems to ..

the thermocouple creates a PD between the two sides

Then current flow / whateverr ;-)

PD operates a solenoid which opens the gas valve

So they can do that directly can they (that was the bit I was unsure
of ..?)

[1] I *could* waste time trawling the sheds to get a universal
'device' that is difficult (or wont) fit, function correctly or sort
the problem at all, when one of the gurus on here could potentially
refine all the above from experience. Maybe everyone has forgotten all
the older stuff and only talk condensing boilers now? ;-)

Personally, if she can survive without it until tuesday, I'd wait and
make sure you get the correct bit

Well, we went out cycling today so didn't get the chance .. Mum's ok
about it so Tuesday it is ;-)

All the best ..

T i m

On Mon, 29 Aug 2005 17:40:32 GMT, T i m wrote:


The pilot heats the thermocouple

Seems to ..

the thermocouple creates a PD between the two sides

Then current flow / whateverr ;-)

PD operates a solenoid which opens the gas valve


More precisely, the current through the solenoid creates a magnetic
field that can hold the gas valve latched open assuming it was already
opened manually by pressing the "Push and hold" button, after the
button is released.

Thermocouples always involve 2 dissimilar metals which are
twisted/clipped/crimped together at the "Hot Junction". This set up is
prone to the hot junction connection getting oxidised/loose and going
high resistance. Maybe only apparent after some time at high
temperatures. This may /may not show up un a high impedeance DVM

So to be honest the best test rig for a boiler thermocouple is a
boiler and not a DVM.

So they can do that directly can they (that was the bit I was unsure
of ..?)


Yes the thermocouple can generate enough current to operate the
electromagnetic gas valve. Or rather continue to hold it latched open
after the requisite 90 ? seconds, if pressed manually and the pilot
lit

DG

On Mon, 29 Aug 2005 19:48:01 +0100, Derek ^
wrote:

More precisely, the current through the solenoid creates a magnetic
field that can hold the gas valve latched open assuming it was already
opened manually by pressing the "Push and hold" button, after the
button is released.

Understood ..

Thermocouples always involve 2 dissimilar metals which are
twisted/clipped/crimped together at the "Hot Junction". This set up is
prone to the hot junction connection getting oxidised/loose and going
high resistance. Maybe only apparent after some time at high
temperatures. This may /may not show up un a high impedeance DVM

Ok ..

So to be honest the best test rig for a boiler thermocouple is a
boiler and not a DVM.

;-)

So they can do that directly can they (that was the bit I was unsure
of ..?)


Yes the thermocouple can generate enough current to operate the
electromagnetic gas valve. Or rather continue to hold it latched open
after the requisite 90 ? seconds, if pressed manually and the pilot
lit

Understood.

Ok, now with a clearer path and thinking electrical here, I assume the
copper tube that carries the voltage to the valve is copper for the
outer conductor and a second, inner conductor in some form of
heatproof insulator (maybe like Pyro?).

Anyway, on Mums boiler, before the 'thermocouple' enters the regulator
/ valve it seems the 'outer' is cut and supported with some form of
rigid insulating material. At either end of the breach there are Lucar
type tags and a pair of short wire going off to a small round device
maybe 40mm dia and 20mm long? I can't remember what was at the back
but in the middle there is what looks like (now I think about it) a
reset button? Could this be some sort of positive gas pressure
failsafe or the end of the upper limit stat? It might 'continue' the
conductivity of the outer .. or not if it 'actions'? If it does work
like that I should be able to isolate it and test the thermocouple by
simply shorting the connectors shouldn't I?

All the best Derek ..

T i m