www.jec.org.uk

Having issues with the air con only blowing cold air, no hot.
Any ideas?
Cheers
Dougie

Move to Hampshire

It's likely to be blend flaps/servos. You should be able to hear them moving when you adjust the controls, if they aren't excercised regularly they can jam.

That would probably be a good call the car has been in the garage for the last 11 months,will give it a go, thanks.

Just to be sure, does your car's thermostat work? (IE: does the car reach normal operating temperature and remain there or does it keep rising?)

I'm sure it's not what I'm thinking it is but best to be sure, 'eh?

first thing to check is the bulkhead mounted heater valve operating, works on vacuum , default is hot, unless the lever and or valve has seized, common issue

without this valve working, no hot water goes to the in car heater matrix


BB

As Dougie hasn't responded since last July perhaps he has solved his heater problem. Without the original author updating their thread there's no much point in us speculating further.

very true,

DrSeb raised it from the dead....


still, the advise is still relevant

BB

very true,

DrSeb raised it from the dead....


still, the advise is still relevant

BB

Sorry I thought the updated forum meant everything was new - didn't pay attention to dates I will now

very true,

DrSeb raised it from the dead....


still, the advise is still relevant

BB

Sorry I thought the updated forum meant everything was new - didn't pay attention to dates I will now

no worries, one of my posts from nine years ago was pulled to the top yesterday , lol

the main thing, is that the info is still of use , and bumping to the top can and has helped others just browsing

BB

Hi,

so my recently acquired 79 car has this problem - plenty of cold air, no hot air.

Symptoms are as follows:

Rotate Temp control (cold - hot, hot - cold) on Auto and plenty of air flows, but the amount doesn't change; temp goes from cold to not quite so cold - a just, only just, discernible change. No sounds of motors, no faint whirring. Airflows from centre vents and footwell vents; regardless of Temp control setting, it doesn't change.

When I select High or Low setting, the volume of air flowing changes, but still no other noises or significant temp changes and it is still from both centre and footwell vents. When I select Demist, the air to the windscreen does increase, but still no temp changes. No motor/whirring noises at any time.

The heater valve is new, and is fully deflected to driver's side when engine hot. The hoses either side of the valve get warm (although they are squeezable - should they be?), and, if I disconnect the vacuum hose, the valve lever deflects the other way - and I can feel the vacuum on the end of the hose, so I think that's working properly.

A little while ago I had some work done to the unit as the flap motors were constantly whirring - as if constantly changing flap positions. Now I get no whirring; would I be right thinking the flaps have stopped working entirely? If so, how to be sure? And then if it is them, how do I access them? Or even check the fuses? Are they behind the panel under the dash, or are they behind the 'cheek' panels on the centre console (which I think I've heard about elsewhere)? If they are under these, how do the 'cheek' panels come off - I can only see 2 screws (locating the footwell vent cover), are these all that holds it in place? I have heard that you can sometimes 'tap' the flap motor or mechanism under the dash - but having looked under both sides, I can't see what that suggestion refers to.

Any assistance gratefully received, as I don't yet have any maintenance manuals. I have thought about taking the car back to where the unit was worked on - but it's a 700 mile round trip from where I now live and not really feasible.

Many thanks, Ray.

I also have no hot air on my car. It to has sat for 2 years whilst repairs were carried out. Could someone tell me where the Bulkhead mounted heater valve is?
Many thanks

The heater valve on a V12 is mounted on the bulkhead near the top and in the middle. Its easy to see and looks like this. On a 6 cylinder car it is a similar unit but may not be bolted to the bulkhead but in the heater hose in the area near the back of the engine.
They look like this

Thank you David