FOUND C19704 N.O. S. WANTED

[cass3958]

Jose since I put that link on they have changed the picture and you are right this is the original heater valve but at £175 its a bit steep for me even though it is the original NOS and will last the life of the car now with the anti rust inhibitors they add to antifreeze these days. You mention the alternative heater valve from the Daimler which has to be reversed but actually there is a version of this which is supplied by SNG Barratt that has the correct flow valve for the S Type which I bought and only £52.20. This is permanently closed then opened by the vacuum as the original but the switch is operated by a lever and the fluids do not come in contact with the vacuum side of the switch as the original did. Should last longer and although it does not look the same and the mounting point is different it works and does not leak. This is a link to the UK SNG Barratt web page for the valve.
https://www.sngbarratt.com/uk/#!/Englis ... 65abeffc48

[Jose]

Cass,

that valve sold by SNG Barrat is a XJ-6 Series 1 (1968-1973) Heater Valve which like the original C19704, opens-with-vacuum, normally closed.

In 1974 Series 2 XJ-6, Jaguar went to a normally open, closes-with-vacuum heater valve.

So you have a Series 1 XJ-6 heater valve in your S type.

Actually, ANY normally closed, opens with vacuum heater valve does the job, no matter what brand. I have a Ford Galaxy repalcement heater valve in my S type, does the job.

The issue is one of originality, some of us want the real C19704 heater valve.

[cass3958]

Just seen this for sale on EBay https://www.ebay.co.uk/itm/Jaguar-Heate ... ondition=4
£200 quid for a used one that has no guarantee that it will last more than a couple of weeks as it is already 50 years old. The man selling it must be mad and anyone who buys it at that price must be insane .

[Jose]

Cass
I have 3 or more of those valves. All Dead Rest In Peace. They look fine until you circulate hot coolant and put vacuum pressure on them. Hot coolant, not water. Easy to test with water. but hot coolant is the acid test. They start leaking through the weep hole on the side and then you get a cloud of white smoke through the exhaust!!

[David Reilly]

The C.19704 Valve (Vacuum Operated) controlling water supply to heater (plate 88 no 28) is no longer available. NOS and used ones do rarely come on the market.
There are a number of options when yours fails:
1 When my heater valve failed and blew coolant all over the engine compartment last year, I installed manual valve on P1B79909DN. I could have in ‘on’ or ‘off’. One advantage is that the 195°F (90°C) coolant can’t leak past the valve making the outside air coming through the cowl vent even warmer! I have now installed a NOS c.19704 that Jose found.
2 The Ford heater valve, Part No. 74614, plastic, made in China, will fit in the same area as the original heater valve. You need to buy the version that is NORMALLY CLOSED / OPENS WITH VACUUM because the same part number comes in the two different operating modes. Sprayed flat black it would probably look OK.
3 A company in Australia (www.advancediaphragmoptions.com) rebuilds vacuum actuators. They told me “Most often the corrosion has made repair not viable. If the aluminium housing is ok it is fixable. (About one in ten so send as many as you can in hopes of getting one rebuilt)
These are a unit that rely on three things working properly.
1.The activating diaphragm.
2.The water sealing diaphragm.
3.And the heater valve seat.
If they are suitable to repair cost can vary from AU$150-275
All the parts need to be made to suit. Nothing is available as a repair part.”
Cheers,
David

[cass3958]

Cass
I have 3 or more of those valves. All Dead Rest In Peace. They look fine until you circulate hot coolant and put vacuum pressure on them. Hot coolant, not water. Easy to test with water. but hot coolant is the acid test. They start leaking through the weep hole on the side and then you get a cloud of white smoke through the exhaust!!

I have the same number of old ones that leak as soon as you fit them in to the system and allow hot coolant to go through them. I have also posted a photo of what the inside looks like on an old one when they start to rust out. It is not the diaphragm rubber that perforated on mine but the inside had rusted allowing the water to pass through the centre metal section of the diaphragm.

[Jose]

three options:

we can try to have them reproduced in China, they would require a minimum order. And the cost of tooling is exhorbitant. Then owners will not pay the resulting price per unit.

we can try to have them rebuilt by the Australian firm. I am thinking that is the way to go. So don't throw yours away.

forget the whole thing and use a modern replacement which will be inexpensive and more available.

[cass3958]

I think it depends on whether you are looking for function or concours. The one I now have on the car which can hardly be seen where it is positioned works fine so I do not require an original looking one. Besides it matches all the other none standard stuff I have on the car.

[Jose]

this is the case of when concours isn't exactly "better".

Jaguar redesigned the MK2 heater system because it was problematic. I hear about it all the time from MK2 owners.

the next generation of Jaguar Saloons all used the C19704 Heater valve, the S type, MK-X, 420, and 420-G, and the Daimler versions and the Limo, although the limo used a different mounting and the heater valve therefore has a different top aluminium half. I also was told it works in reverse. (normally open, closes with vacuum).

If you search online for "normally closed opens with vacuum heater valve", you get thousands of results. They are still being used.

[cass3958]

That vacuum switch I highlighted for sale on EBay has been sold. Someone hit the buy it now button for £200. Fool.