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Renault Laguna I - Phase 1 - Heating and Cooling - Possible fix for cold heater

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#1 · (Edited)
Hi everyone, (and particularly those of you with cold heaters!),

This post relates to a Phase 1 Laguna 1.8 RT (95/96 vintage), conventional heater (i.e. no air-con), but I suspect much of it will apply to other Renault models. While I can see no reason why this approach would be any different on a model with climate control, it would appear that if removal of the matrix ultimately becomes necessary, it is much more difficult / convoluted than on a model without......so bear this in mind.

This job, start to finish took me about 1.5 hours.....but I wasn't rushing.

Usual problem - heater output poor for a few weeks & then nothing, just freezing cold air (which in this weather isn't funny.)

Before I continue I should say that the heater is now belting out bucket-loads of hot air so you might want to read on........(but this is going to be a long-ish post!).

NOTE:- ALSO.....I've included a follow-up at the end of this post which seems to highlight the heater core as a natural 'trap' for a dirty cooling system.......i.e the problem can come back quite quickly. Strong pointer here for giving the ENTIRE system a clean and flush through first otherwise the muck will accumulate in the matrix again.

** Pics added by request, but I'm not up for dismantling it all again.....so you'll have to imagine what an exposed heater pipe looks like!
:)

NOTE: The engine needs to be up-to-temp and be sensible - you're dealing with hot water under pressure - don't end up getting scalded!

1) Is the heater matrix actually getting a flow of hot water?

Holding /feeling the heater pipes where they emerge from the bulk-head in the engine bay is probably going to be a red-herring.....they'll get at least warm (& probably hot) from the circulation of the coolant at the top-end in general, (heat conduction).

To really find out, take 5 minutes to pop out the glove box tray - 7 Torx head screws on mine (4 top & 3 bottom - under the bit of 'carpet').



Once out, look through the hole and to the rear / right, you'll see two large-ish (1" dia) pipes angled upwards and disappearing through the bulkhead. Mine are bright aluminium colour.



Get your hand in there and feel both pipes - are they both hot? If not or if one is cool compared to the other then the flow through the matrix is probably restricted or completely blocked, or possibly got an air-lock ( have you been doing anything with the cooling system recently?)

2) Air-Lock:-

This is the simplest / least effort approach thats always worth trying first......(especially if you've been 'doing things' to the cooling system recently).

Don't be too disappointed if it doesn't sort your problem though, simply move to step (3).

Anyway........

Under the bonnet ( just to the left of the brake servo) you'll see the heater connection bayonet....a plastic twin-tube moulding with rubber pipes attached and probably a blue (sometimes black) lever on its right hand side.

On the top hose you'll see a small plastic thumb screw which is the air bleed. With the engine warm and idling (remember....HOT!)....undo this screw ( an old towel is really useful here), and see if coolant OR bubbles emerge. Be careful about taking the screw right out because if the thermostat is open the coolant will almost certainly jet out some 12 or 18".

***Its not impossible for gunge to have blocked the hole, so (with the screw out - CARE!), clear hole with a piece of wire / thin rod.......just to be sure.



If there was lots of air in there, wait until the bubbles stop - i.e uninterrupted fluid comes out, close the bleed screw and re-check the heater.

Is it warm /hot? If so great, top-up the header tank if necessary, refit glove box and you're done.

Heater still not hot? then:-

2) Flushing:-

a) Getting the pipe connection off........

If the engine is now hot, let it cool down a bit and when safe, release the pressure in the system by taking off the header tank cap.

For this next bit, the airbox top and intake air pipe WILL get in your way so take a few minutes to take 'em off and put carefully to one side.

*** cover up engine intake etc with plastic bag or similar to prevent ingress of water during the next bits***

From a number of posts I read here, getting the heater bayonet fitting off presents a problem - it won't move - this is (probably) why:-

The fitting is supposed to pull off if you depress the lever..... no, it doesn't !

The lever itself is NOT the actual catch - but the black plastic bit it is attached to - IS ..........

Schematic:-



What you are supposed to do is pull the outer end of the lever away from the connector thereby making the bulkhead end push DOWN on the catch (which is hard to see) ...thereby releasing it

This still didn't work for me - the lever was getting in the way rather than helping. I carefully prised the lever off ( hinges on two small plastic pins).

You will now be able to better see the black plastic lever / catch which actually has a stepped lug at the bulkhead end ( although you can't see that bit). This is what locks the fitting in place and is what is stopping you getting the fitting off.

I found that inserting a flat screwdriver into the outside edge of the opening this tag passes through and levering (carefully) to make the plastic move INWARDS towards the pipe is what releases it. A couple of sharp tugs and the fitting came off exposing the heater matrix inlet and outlet pipes.

Don't lose the 'o' rings IF they pop off.



b) Hose bit:-

Run out the garden hose.

Select whatever nozzle you have that presents a reasonably good fit into the open pipe(s)......(this is also why you need the airbox out of the way!).

Squirt water into the top (bottom) pipe......does water emerge from the bottom and vice-versa?

No? None at all ? Matrix is probably well and truly clogged. Repeat on alternate pipes a few times to see if you can dislodge the obstruction. You are going to need at least some flow at first in order to flush it out.
If you can't get any flow at all - no matter what you do, it might be best to consider a new core at this point.....you've already done about 1/3 of the work needed anyway.

Someone suggested elsewhere in this forum to used a compressed air line to blow the debris out.......again your choice, but if the matrix is well and truly blocked, 60 or 70 psi has a good chance of bursting the core.

I did use compressed air once I was sure the core had a reasonable flow through it......and yes it did shift some additional crud.

Mine had a very small flow at first and it was absolutely 'chocker full' with fine red sludge.

c) Treatment:-

The next bit is your choice:-

There are various flushing agents out there, most based on weak organic acids which'll take about a year to de-scale a cruddy heater core - if ever.

I made up an adapter with a cork, a small piece of pipe, a plastic tube and a funnel. This was plugged into the bottom pipe.



Into this I poured about 1 litre of "path clear".....i.e the one that contains dilute hydrochloric acid.....this works on scale very quickly by comparison to "kettle de-scaler".



NEVER, EVER use a liquid that is alkali (caustic) based because alkali materials dissolve aluminium very efficiently.......and the heater core is?......aluminium!

Some material will spill out of the top pipe.....keep the hose handy to keep rinsing off the various bits it WILL splash on. (Goggles are a good idea from here-on in).

Leave for about 5 mins and back flush, using the hose on the top pipe - I bet lots of crud emerges. Reverse the flow.......more crud.....and so on.

I repeated the acid treatment 3 times but on the last time blew the water out of the core first using compressed air......i.e to ensure that ALL the liquid in the core is dilute acid.

3) Finishing off:-

If you are satisfied that you've pretty much got all the debris out that you can, give the core a good run through with clean water to wash out any remaining acid and thoroughly wash down the rear engine bay area.

Jet wash the bayonet connector inlets......they'll be filthy as well.

If you took the (blue?) release lever off, refit it to the bayonet now.

Align bayonet and push fully home on heater pipes - it should click into place.

Dry-off the various engine bay bits and re-fit airbox.

4) Re-filling:-

If you didn't lose too much water, start engine....(top-up a bit if necessary) and run until it gets warm.

Keep opening the heater core bleed valve (care!) to get the air out.....you want the thermostat to have opened to really push the air / water through.

When you're happy the air is out, close the bleed screw, top up header tank, (you've lost antifreeze so put some back), check that everything is back in place / tools in their trays.

Get back under glovebox.....are those pipes now both hot?

If so you've almost certainly got your heater back.

Additionally, while you're there, the large black rectangular plastic 'pipe' -just to the left of the heater pipes (see pic no.2), has a circular (3" dia) electrical 'gubbins' set in the top of it?.......this is the blower motor resistor pack. If your blower packs up its almost certainly one of the resistor coils 'gone' or - as is often the case - the thermal fuse inside it. (See other threads on this site.)

Refit glovebox.

Check everything is re-fitted / tight.
Check water levels
Check for stray tools.

Close up car.

Hopefully, you've got heat back again.

Bear in mind that this process might open up leaks in the core if it was best part rotted before you started.

keep a close eye on water levels at first and a 'nose' for nasty damp smells in the car. If you do lose water, check the carpets in the footwells- if wet you'll know why......you need a new core.

Hope you find this useful.......would be interesting to know how many clogged heaters get 'fixed' this way ??

Regards,

Spiro'


Footnote on Acid Cleaners:-

For those harbouring concerns about dilute acids......

Most de-scalers etc, are based on weak organic acids such as Acetic acid(vinegar if you like) or citric acid('lemon juice'). These materials will dissolve carbonates such as lime-scale, but they are chemically classified as 'weak' acids and as such the process is slow. They do not dissolve rust deposits but might help loosen them. Because of the 'gentle' action they are deemed safe for the general public and are unlikely in the extreme to harm anything they are put in.

Mineral acids, (Hydrochloric, Nitric, Sulphuric etc), are deemed strong acids and in their concentrated form are aggressive and hazardous. In the case of 'path clear' type materials, Hydrochloric acid is the active agent, and as supplied is already diluted to about 5 or 10% with water. At this strength it will vigorously dissolve lime-scale/carbonates and will attack many metals including aluminium. I tried the solution (above) on a piece of freshly abraded Ali' first - the reaction was very very slow, however it rapidly dissolved lime-scale - which is what we are after.

It does not readily dissolve copper although the brown /black tarnish (oxide) may be removed.

It will also irritate the skin (itch) so wear protective clothing / goggles and have a hose to hand to quickly wash off any spills/splashes.

In the case of a blocked heater (which nowadays is likely to be made of Aluminium), any contact with dilute Hydrochloric acid should therefore be kept to a minimum, (say 5 to 10 mins total). I decided that the approach with ours was 'kill or cure'.....it was useless anyway!

If in doubt try to blow most of the water out of matrix with compressed air (providing its not completely blocked - see above), and back-fill with 'kettle de-scaler' or 'Rad-Flush' and leave for an hour or so......then back-flush with the hose. It may(?) be enough with yours.

Alkali:- Caustic soda / Sodium Hydroxide / oven cleaner/ 'Lye' ........ vigorously attacks Aluminium - do NOT go there!



UPDATE:-

One week into 'repair'.......Heater working fine and no leaks!

UPDATE 2:-

Ten days into 'repair' and heater getting colder again !!! Took off connector (getting a dab hand at this - 8mins), and lo and behold MORE sludge. The heater must act as a trap on this system OR more debris has loosened-up. Quick backflush with hose and all fine again......total time 22 minutes.

UPDATE 3:-

11 days in and would you believe it.....heater getting cold again AND more brown sludge. This is clearly debris from the rest of the system 'collecting' rapidly in the heater core which is a low point on the system.

Put a large bottle of 'Rad Cleaner' in the system and took it for a 20 mile drive. Disconnected top hose at stat' end (easy) and pumped block through with a pressure hose jammed in the rad's top hose.....(stat will close when cold water reaches it though). Disconnected bottom rad hose at engine block end (again, easy) and pumped water through the rad.......a lot more rust sludge came out. Continued until water ran clean then re-connected and re-filled. Backflushed heater (again) for good measure.


UPDATE 4:-

14 days in and heater now hotter than it has been in a LONG while - in fact on 'full' it becomes stifling and uncomfortable. Thats the ticket!

UPDATE 5:-

4 weeks 'in' and still fine!

UPDATE 6

6 months in and still A-OK
 
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7
#27 ·
Laguna heater rt estate

Brilliant diagnosis , had the problem flushed system , had it not been for this link ,I was getting mad!!! I would have been scratching my head again! especially the matrix bayonet fitting , spent 3 days buggering about before , saw the picture and wallah , sorted ,off like a gazelle. heat is still kinda cool but will reflush tommorrow . (now where is the pollen filter)!!!
cheers a diomand link this one
regards Trapper
 
#30 ·
renault laguna rt estate

Spiro many thanks for all the info, now sorted heater switch, it was the thermal fuse, Renault wanted £56.98 for a replacement, ordered two from maplins 110c arrived next day , cost 61p each, job done and dusted . Heater matrix reflushed today , lotsa crud , job sorted, I now revel in heat and I dont want to switch off the engine :) Pollen filter £14.98 from halfords, (when i checked there wasnt one in situ)so now thats sorted, in all excellent results easy to follow schematics from yourself , you should be a mechanic!!!!;) in all brilliant , and to all you readers out there, info from the site was spot on.
many thanks Trapper.
 
#32 ·
heating problem

my heaters are cold and ive tried to fix this for a few weeks now my 2 heater pipes are boiling hot i checked this after i had removed the glove box and when i removed the bleed screw the water hit me in the head im confised as why is the heater still blowing cold air into the car i have also flushed with garden hose
 
#34 ·
my heaters are cold and ive tried to fix this for a few weeks now my 2 heater pipes are boiling hot i checked this after i had removed the glove box and when i removed the bleed screw the water hit me in the head im confised as why is the heater still blowing cold air into the car i have also flushed with garden hose
Even If the water is spurting out of the bleed screw that does not mean that it is coming from or through the heater. It can still have an air lock somewhere.

For instance if you clamp of the pipes in and out to the heater you will still get water coming out of the bleed point because the system is such that the pump is still working water through the system. If the water was stopped pumping through the system by a heater blockage the whole engine would overheat wouldn't it? So there has to be a flow from another source to counteract this potentialy disasterous scenario.

That one threw me for a while with my Espace heater. Water pump changed - no heater drivers side. I could not understand why as there was hot on both pipes to the matrix but no heat and water jetting out of the bleed screw. Then the penny dropped.

It was a persisting airlock causing the problem. The remedy would take too long to go into. But basically I had to drill holes in the matrix unit inlet/outlet plastic moulding under the dash and fit bleed screws. That finally got rid of the air locks and got my heat going again - and that after two days of constant bleeding. What a job!
 
#33 ·
Hi m8y,

That'd have me scratching my head as well at first :)crazy: ), but logically........

1) IF the heater flow and return pipes behind the glovebox are both truly hot (once car has warmed up), then there must be hot water flowing around the matrix.

Its important that you ARE checking the pipes under the dash because the piping that emerges near to the cylinder head can get hot through conduction only and mislead you into thinking there is a flow.

2) You're getting a jet of hot water out of the bleed valve which also tends to indicate that there is water flow ....

3) Assuming the blower motor IS actually blowing air out of the ducts, (is it?), then the only reason I can think of (short of a blocked main air pipe / blower motor) for still getting cold air is that the 'hot / cold' duct flap is stuck in the cold position making the blower push cold external air through the car....(i.e. completely by-passing the heater matrix).

What does the hot/cold knob feel like?....gone very stiff? or suddenly slack ? .....i.e maybe the operating cable has seized / broken?

I think I'd go back to the glovebox out stage and with the aid of a torch see if I could verify that the hot/cold flap IS actually moving to and fro.

If its none of these then I agree - its very odd indeed!

let us know how you get on......I'm fascinated now!

:)

Spiro'
 
#35 ·
help

update
i missed this one pipe hot one luke warm

still pooer flow of water through the heater matrix
i need the ratio of path clear to water
how mutch water to how mutch path clear

is it 3 ltr water to 1 path clear
can someone tell me the exat ratio
in ltrs
ie how mutch water in ltrs to how mutch path clear
sorry for being thick
benn playing with the car all day
 
#36 ·
update
i missed this one pipe hot one luke warm

still pooer flow of water through the heater matrix
i need the ratio of path clear to water
how mutch water to how mutch path clear

is it 3 ltr water to 1 path clear
can someone tell me the exat ratio
in ltrs
ie how mutch water in ltrs to how mutch path clear
sorry for being thick
benn playing with the car all day
It is aready diluted read spiro's instructions again. Use it straight from the container.
 
#37 ·
As per above post.......

The Q&B stuff (for example) is not that strong in the form supplied (about 5% HCl / 95% water), so you can pretty much use it from the bottle. If you're worried, dilute it 50:50.

(Even at 5% it will however irritate the skin quite quickly so gloves / googles & running water to hand......)

HCL at this strength attacks Aluminium quite slowly so two or three 10 minute 'exposures' is unlikely to do much harm (unless the core has become paper thin over time), but DO NOT leave it in there for hours and hours (e.g. over-night).

As long as you have SOME flow through the core the acid can get ( and needs to get) through the entire matrix ( uncoiled it'd probably be about 8 or 10 feet long) in order to get to work on the limescale therein.

If you have NO flow whatsover then the acid won't work beyond the first few inches of the heater pipework.....so don't waste your time.

Hydrochloric acid won't dissolve the rust deposits, just loosen the limescale that its all bound up in....hence the need to pump it through with a garden hose to blast out the red muck.

I needed to repeat this about 3 times before it finally stayed clear - which also seems to be the experience of many others who've posted here.

For reference, a clear / clean matrix allows a VERY substantial flow of water through - close to the flow rate of the garden hose itself - so if it "ain't pouring out" after treatment its probably still partially blocked.

Gently rinse everything down afterwards to get rid of any last traces of acid - cover up the electrics / intakes for obvious reasons.

Best of luck.........

;)

Spiro'
 
#38 ·
heater matrix

Thanks for posting all the info on heater matrix i have been trying(without sucsess)to remove the heater bayonet.I know its blocked but now maybe i will be able to flush it. .Just hope the matrix isen't leaking as my car has air con which the manual says have repaired at dealers. thanks again
 
#40 ·
Kinky But Satisfied

Well Done spiro for an excellant fault finding thread which I followed and in my case discovered it was simply the garage
repairer had put the heater pipe back with two folded kinks in it where it loops under the large hose to the turbo.
simple if you you know about it but hard to see without careful exploraton
Many thanks for a great article
LAGUNA
 
#42 ·
HEATER MATRIX - Bulkhead connector PROBLEM !

Hi Guys,

Thanks to SPRIOCHETE my Heating problem is errrmm Better :) .
Found n the end it was easier to remove the matrix complete to flush it out. Took anly 30 mins to remove and 30 mins to fit its pretty easy but i was 1 ½ Hours flushing it out.
Since refit heating has imporved dramtically but I have been losing water. When I originally disconneted the bayonet from the bulk head the seals fell out and i found 2 of the Teflon rings were damaged. I can't find anywhere including the trusty old haynes manual that describes what the configuration for the seals should be ??????? :eek:
Rubber Contoured ring / teflon / "o" ring ??
Problem I now have is I cannot get the Bayonnet to Click back in place with the current seal configuration. I have been trying to lever the bayonet with a big iron bars and I am a big lad (hence the Nick SHREK) but to no avail. It just won't click and lock in place so i have a constant leak which requires topping up regularly. Any tips or advice at this stage would be most grateful. Especially the Correct Seal configuration . Ta
Regards
Shrek288
 
#43 ·
Hi 'Shrek',

From memory, both my bayonet seals were just plain black (neoprene?) rings.

It might be that if your bayonet won't stay locked in place then the plastic retaining catch (on the RHS of it) might not be engaging properly?(see schematic diagram in my original post)

If this were the case then the pressure build up in the cooling system would more than likely start pushing the bayonet off causing a leak.

Just a thought but worth double checking?

Spiro'
 
#46 ·
Hi, I'm new to the forum, found it when I was searching for a solution to a juddering (missing) problem with our car.

we have a Laguna 1.8 RT, petrol, (1998) We had problems with the heater since we got the car several months ago but they appeared to be fixed after DH put a new thermostat in. within a few weeks, the heater was blowing cold (or lukewarm) again.

When DH took me for art supplies a few days ago, I saw the gearstick shuddering. Being a contrary little madam, I asked him what the problem was. Smarty pants replied that it was because he pulled away in 3rd gear. I accepted that explanation until I saw the gear stick shaking again a few yards down the road. He'd dropped to 3rd gear when approaching school crossing. So he said perhaps the neighbour hadn't put the water cap on properly earlier (when they were both trying to find out what was wrong with the heater) He stopped at a layby, checked the water cap said it was a bit loose (the lying toad!) But as we drove on, each time he was in 2nd or 3rd gear, that gearstick was shaking like crazy. He continued driving with one hand on the gearstick to stop it shaking and to shut me up.
I can't see how this problem can be connected with the heater, but he decided to follow spiro's advice in this thread(many thanks for that, one of those pipes is pretty bad)
He'd already used up all my pathclear so had to go buy more. He wouldn't use my kettle descaler ( I reckon it would have worked)
He's still outside with the car so I decided to ask if anyone here can offer any advice.

The only sense I can get out of DH is that the car is pinking a lot when driving at 30mph in 4th gear, if he drops to 3rd gear it still misses but doesn't judder as much. (he hasn't got up to 5th gear since this started) He says the power is still there, in that the car pulls away easliy but the engine isn't running smoothly.
Does anyone have any advice to offer.
I'm disabled and can't get out of the house if the car isn't working (and I won't go anywhere in cars that have problems like this)
Many thanks in advance.
Maggie
 
#47 ·
Hi Maggie,

Glad the heater hints seem to have helped.

The shaking gearstick problem you cite may well be addressed in another thread (anyone here seen such?), but I agree that it sounds like a misfiring problem.

Given the engine is transverse mounted, any hic-cups / coughs and splutters will result in the engine rocking itself sideways and hence macking the gear lever jump about in an up / down & front to back direction.

Causes can be many and various - but first port of call is usually plugs / leads / distributor cap - i.e. ignition electrics.

(in passing - you hadn't driven through a large puddle or similar just before had you? - water sprayed over the ignition components can cause a ragged, jumpy misfire).

Others may want to advise further - but I know our Laguna 1.8 RT HATES water on the cap and plug leads.

Failing that - if it persists - fuel problems can cause similar effects.

Regards,

Spiro'
 
#50 ·
Glad a few others have had a result from this approach to the problem..... Definitely not one from the Renault workshop manual - but neither is the cost!

Doesn't work for everyone, but looking back over the replies it does seem to solve the issue in about 70% of cases...... that must mean its worth having a go.

PS.... our Laguna is still OK heater-wise a year+ down the line.

:)

Spiro'
 
#52 · (Edited)
Hi,

There are a number of threads addressing exactly this issue so a SEARCH would turn up the answer your looking for......

The most likely cause is a blown thermal fuse in the resistor pack - the glovebox picture at the start of this thread shows where it is.

Remove the cable connectors and locking screw and twist and remove the plastic moulding containing the resistor coils and thermal fuse, up and out of the main air pipe....be careful not to damage the coils. (Ignore the automatic hyperlink that links the word 'coil' to ignition coils - nothing to do with this problem).

Once on the bench, carefully remove the metal cover using thin pliers to untwist the locking tabs - note which way it fits back on.

Inspect the coils for any burning or breaks.

The thermal fuse is the small 'bullet' shaped device at one end - put a simple continuity meter across it to see whether it is conducting. If not its blown.

The temperature is printed on the outside (about 100'C) you'll need to get one from Maplins or RS - again various threads list the part number(s). Get one that can handle a significant current - suggest about 10 -12 Amps.

As its a thermal fuse, soldering risks heating the fuse to a point where it 'pops' again. Cut out the old leaving enough lead to attach the new and either solder the new one in place with some sort of heat-sink on the fuse body OR attach with a mechanical connector at each end.....the metal terminals inside a 'chocolate block' strip have been suggested as quite a good way to do this.

Quickly check it is still conducting with your test meter - carefully re-assemble the pack and re-mount in the main air tube.

Its a good idea to inspect the main tube / blower fan casings for blockages -(usually leaves and twigs), which might have caused the over-heating problem in the first place.

Your blower control will probably now work.

Alternatively, buy a new resistor pack from Renault - about £60 I gather!

Spiro'
 
#53 ·
Piggin' cold heater !

Howdy Spiro!
I'm a 1st time forum virgin, please be gentle :eek: . I've got a Clio Mk1 with the dreaded cold heater syndrome and i was wondering if it'd be worth flushing the entire cooling system with the miracle 'B&Q cleaner' or do think that it may do more harm than good Cheers
 
#54 ·
Re: Clio.....

Hi KatFlap.....

On balance my answer to that would be NO, don't do that........not unless you have reason to think the ENTIRE cooling system is really in a mess.

A couple of reasons why......

1) Filling the entire system with dilute acid will generate quite a lot of Carbon Dioxide (CO2) from the dissolving scale, which if trapped by a sealed system (Rad cap on) will likely blow out somewhere through the pressure build up.

2) The water pump is designed to get part of its lubrication from the anti-freeze, replacing it all with Q&B path-clear risks damaging the pump bearings.

If you really want to run it with a flushing agent for a day or two before attempting to clear the heater core, use a proprietary cleaner sold for the purpose.......but if the heater is very clogged I doubt this will shift it.

Try to employ the general principles I outlined for the Laguna on your Clio's heater - From the posts sent back, it does / has worked for quite a few people.

Best of Luck!

Spiro'
 
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