S4 heater blows cold

[professor]

:cry: Hi..my 1970 S4 heater blows hot air from the left hand, passenger, vent, and cold air from the right hand vent ! How can this be and do I have to dismantle half the car to fix it ?

All replies gratefully received. Cheers. Andy

[Mr.Gale]

The heater in my S1 only works in the summer.

Gale

[holywood3645]

You could try to flush is and if your lucky it may clear. I just restored the one in my S4 and sorry to say you have to remove the dash to get it out.

James

[alan.barker]

I would suggest as follows: Put the front of the car on ramps to prevent airlocks. First i would fit a new thermostat, which is always a good idea so the engine reaches running temp quickly.
remove heater hose at the cylinderhead and connect to garden watering hose. remove heater hose from front carb side of engine. Turn on garden water supply to flush out sediment from heater matrix. Reconnect heater hoses, fill with a good quality anti-freeze and bled system.
Alan B

[elansprint71]

Do you mean it blows hot/cold through the vents near the windscreen or hot/cold from the lower vents? If it is the upper ones, I suggest that you have a pipe off somewhere.

[oldelanman]

:cry: Hi..my 1970 S4 heater blows hot air from the left hand, passenger, vent, and cold air from the right hand vent ! How can this be and do I have to dismantle half the car to fix it ?

All replies gratefully received. Cheers. Andy

If the demister and eyeball vents are working on the RHS, is it simply that the RH footwell flap on the heater box is closed ?

Regards,

[professor]

Thanks for replies.

The odd thing is I have fitted a new thermostat and back flushed the heater matrix but no difference. The heater flap is open and the eye level vents both distribute cold air. However, and this is the odd bit...the heater air out of the LH vent is very hot but out of the RH vent it is cold. So I guess it can't be an air lock as both would blow cold ? It only has one heater matrix. I wouldn't mind if it was the other way round although my wife might complain ! The only way to heat the interior now is to shut the RH vent and let the heat circulate from the passenger side. Not good.

[GrUmPyBoDgEr]

You seem to have the coolant side of the system sorted so could the problem lie with the air side of the heat exchanger matrix?
Maybe the fan shroud is broken or there is an air leak or a matrix block of some sort?

In any case good luck & hope you get things working.
I'm a fine weather driver & don't envy you your problem.

John

[professor]

Thanks John

Yes I suspect you might be right. The nightmare scenario is that I replaced the dashboard a few months ago..ugh. Also I always seem to be restoring my cars over the summer months and driving them over the winter..some sort of heated garage might reverse this madness !

I have never stripped down a heater box on an ?lan so I guess there is the possibility of cold air missing the matrix. It would have made sense to strip it down when the dash was out but where do you stop ? The last time I took that approach with a Healey 3000 it took nearly four years to rebuild and I sold it the first week back on the road as I hated it ! The neighbours nicknamed the car " you vicious bastard " as apparently that all they heard for years coming from the garage ! I wonder if I still have the nameplate they gave me ?

Best..Andy

[garyeanderson]

heater box is as below

[alan.barker]

if you have hot air on the pasenger side, it means hot water is flowing through the matrix.
Maybe on the driver's side there is a mouse nest If you remove the trim under the dash on the driver's side and open the flap, what can you see inside i think you should be able to see the matrix.
Alan B

[professor]

Hi guys..thanks. Picture tells a thousand words !

So there are two separate radiators in the box ! I thought there would only be one..what happened to " add lightness". Was Chapman on holiday when they designed it ? Even my E Type has only one. My workshop manual is useless on this subject.

So, I guess the RH one could be blocked or would the water not be able to flow to the LH one ? How is it Plummed ?

Or, a mouse nest blocking the airflow..I will take off the trim and poke about.

Cheers..Andy

[ardee_selby]

Hi guys..thanks. Picture tells a thousand words !

" How is it Plummed ?"

Hope the above helps, assuming the S4 system is similar...

Cheers - Richard

[alan71]

I had the same problem when I first got the car. I replaced the foam strips that seal the heater element to the heater box, no improvement. I didn?t notice the way the element fitted left a bigger gap below than above on the drivers side allowing cold air to pass below the matrix.
I couldn?t face taking the dash out again so it stayed on my to do list until I replaced the wiring loom, only 20 years later. Two layers of foam under the matrix on the drivers side and it works perfectly, warm air on both sides of the car.

Alan

[professor]

Thanks guys

No mouse nest I'm afraid. I think the cold air, as you say Alan, is bleeding past the matrix....Ho hum. That will teach me. It may be possible to inject some builders foam to seal the matrix via the outlet. Has anyone tried that or any other fix without taking the dash out ?

I know it sound a bit of a bodge but I use to work with Chapman in the 1970s and he use to say ( amongst other things ) ..." if a bodge works it isn't a bodge " !