Heating and ventilation *** Updated

[Woly64]

I appreciate this is fairly basic stuff but having established that the dashboard heater controls + cables appear to be operating as they should, the fan works properly and the input hose to the heater unit clearly has hot water in it .......then what is the most likely reason I am unable to get any warm air in the cabin please. I'm hoping there is an easy fix which does not involve draining down the entire system but I'm probably just kidding myself! As ever any suggestions are welcome

[JJC]

Could not be simpler. The hose going to the heater box, of course, has hot water in it, but its not getting into the heater element because the cable that operates the opening / closing of water flow has slipped. Just pull off the small plastic cover on top of heater box, and re-attach, or tighten, the cable. Might want to spray a bit of WD40 on everything, and exercise everything, just to ease operation. Easy. Enjoy your new found warmth !!

JC

[Woly64]

I do hope it is that simple JC ....

[JJC]

Can't be anything else. Should take you about 5 minutes.

[Series1 Stu]

Can't be anything else. Should take you about 5 minutes.

Unless the heater matrix is blocked. Might be wise to check that you are getting warm water flowing out of the heater too.

Regards

[Woly64]

Good point Stuart - will get onto it tomorrow and report back

[JJC]

Gentlemen: Of course you are getting hot water thru the return hose. Warm water is going to, and continues back to the engine. Problem is, it is not getting into the heater core, which allows heat into the cockpit. That core will remain cold until you pop off the plastic cover as I suggested. If you need instant heat, you can operate the lever by yourself, and figure out how to make the cable functional later. At least you will have heat. Don't have to chase a mouse.....that's the problem....easy.

JC

[JJC]

FYI Stuart.....if the water was blocked, anywhere, the car would overheat.Its just the heater valve, under the plastic cover. It can be opened by hand. Easy.

[Ole-xke1974]

The simple way to test if you have coolant flowing in your heatercore is to feel both hoses. The inlet and the outlet. If one is cold, your valve is closed/stuck.
There is one more thing to check. At least on my S3 the heaterbox also has a flap that cuts off the air being blown into the heater core. The control is "the other" cable going to the heaterbox. The flap should be in the position that blocks the oblong hole in the bottom of the heaterbox to allow air to move from the fan housing through the heater core.
Finally and not as simple, is that your valve is defect or the heatercore is clogged up with years of deposits.

Good luck ......... Ole

[Ole-xke1974]

Can't be anything else. Should take you about 5 minutes.

C'mon John. I agree that yours is the most likely. As I suggest in my post, there are a couple of other possible reasons.

[JJC]

Such as ? If it is something other then my suggestion, what is it? Also, both hoses going to the heater box have to be warm. If anyone suggests that one hose could be cold, then that individual does not understand the system.

[lowact]

In my case it was not having thermostats, and with alum radiator engine was not getting hot enough. Fitting thermostats fixed this,. What temperature does yr engine run at? Needs to be well into "normal" before heater works like it should, this with reco'd heater incl new matrix...

[JJC]

Hi : In the dead of winter, with an aluminum radiator, and no thermostats, once the engine gets even barely warm, which it will, because its an internal combustion engine lets remember, you will get heat in the cockpit if the by-pass valve is working. If it is not working, and closed, the water will continue to circulate , but not into the heater core. That's why Jag used a by-pass- valve, closed during the warm months to keep heat out (God knows there is enough heat coming into the cabin already !!) Then open in cooler months to a heat the cockpit. All sorts of suggestions, not one of them realizing the heater system is fitted with a BY-PASS valve !! Suggesting something is clogged is ludicrous , because if there was a blockage anywhere in the car, it would eventually overheat, even in the dead of winter. And thermostats, in or out, and an aluminum radiator , will have little or no effect on a properly running heating system. Check the BY-PASS valve under the little plastic cover on top of the ventilation fan housing. If cables are stuck, or broken, just operate the valve by hand.....when you look at it, it will all make sense. Twice a year, I take off cover, and operate valve based on the season. Easy, easy, easy.

[lowact]

C34691 is a regulating/shut-off valve, not a bypass valve. Ref the pic. The RH pipe takes water from the engine. The LH pipe delivers water to the heater matrix. When the control lever (with phillips-head cable clamp screw) is all the way to the left (front of the car) the valve is completely closed, then there is no flow to or from this valve.

[Series1 Stu]

JC
I've got to admire your dogma.
I really don't appreciate being called ludicrous but going off your track record I am not surprised by it.

40 years of messing around with cars while working in mechanical engineering obviously counts for nothing. As for blocked heater matrices, the one in my car must be an anomaly from another dimension.

Regards

[JJC]

Colin ; Thanks so much for the picture ! Helps explain it all. We also refer to this as a by-pass valve, but regulator, shut-off valve, etc., that works. Designed to let hot water , when not needed, to by-pass the heater core, and continue circulating .

As for anyone who suggests that there is a blockage somewhere in the system, and that the only negative side-effect is no cabin heat, that is a ludicrous statement. Any blockage, anywhere, will eventually cause the engine to overheat. Inside, or outside the heater, if something is restricting flow, up go coolant temperatures.
Thermostats, modern aluminum rads, etc, have nothing to do with an in-op, or in-effective heater.

Thanks again for the picture Colin.

Dogma, reputation ?? I thought folks joined these global forums to help one another. If someone makes a statement that is wrong, or ludicrous, and I know differently about that particular subject, or area, I am going to say something before some new owner, or first time E-Type owner, heads down the wrong path.

Happy New Year !!

[mgcjag]

We need to note here that the valve pictured above is not just a simple on/off controled by the linkage...it has a capillary sensing element( that can be seen as a coil in the photo) that positions in the hot air flow from the heater matrix...it operates linkage in the valve to maintain air temperature as selected by the driver.....Steve

[Ole-xke1974]

Such as ? If it is something other then my suggestion, what is it? Also, both hoses going to the heater box have to be warm. If anyone suggests that one hose could be cold, then that individual does not understand the system.

You're right. Literally there is one hose going to the valve, one from the valve to the heater core and one going from the heater core outlet back to the cooling system.
However to state that a loose cable on a valve actuator is the only thing that can be the root cause of this problem is not true. That is a lack of understanding of how the system works.

[Ole-xke1974]

Just to emphasize, the E-type heater valve is NOT a By-Pass valve. It blocks the flow and when doing so the engine does NOT overheat.
A by pass valve, will as the name suggests pass none, all or some of the liquid by. To do so, it needs a by-pass path. A third path to let the liquid back into the system. The Jaguar heater valve has two ports. An in and an out. The posted picture clearly shows this.
I hope, despite some inaccurate statements in various posts, that some insights and help has been provided to the original question.
Please keep us posted ........ Ole

[lowact]