Hi All,


I've got a 1984 4.2 Series 3 XJ6 as my daily driver. The car is bloody brilliant but the heater is pants !
The fan works on all speeds as it should but the temperature side of things only gets to luke warm at best.
The engine gets up to temperature fine by the way.


Any suggestions would be great as its not so much fun in the cold !


Thanks
Darren

 

hi,. If you place the Mode switch in AUTO, and the Temp dial in 85, does the Top Center Vent close, and air comes out only from the Side Dash Vents AND the Floor Vents on each side of the transmission tunnel ?

 

Thanks Jose, ive checked and when I set it up like you say then the centre dash grills DON'T blow but the footwell and side vents DO blow.


I then checked it some more and the centre dash grills DON'T blow any air on any setting. Now you mention it, I don't think they ever have !

 

ok, if the Center Vent is closed when the Temp dial is at 85, that is a good sign since it is supposed to be closed during Heat mode. Does air come out of the SIDE dash vents in Heat mode? -Make sure they are open by rotating the wheel under each SIDE vent- if yes, then the vent flaps are doing what they are supposed to do in Heat mode. Now do the opposite: set the Temp dial at 65, Mode switch in Auto, engine running:. Does the Center Vent blow air?

 

Ok


Air DOES come out of the side vents in heat mode
Temp set at 65 and fan mode in auto, the centre vent opens and air comes out.


So far so good then.....

 

yes, flaps, Servo, and vacuum system are doing their job inside the car. Next check is the Heater Valve, mounted near the center of the firewall, engine compartment, closer to the battery. Run engine until temp is at 90 or 'Normal'. With someone else inside the car, have them rotate the Temp dial, Mode switch in Auto, as you watch the heater valve mechanism under the valve to see if it moves as the Temp dial is rotated from 65 to 85 and back to 65.

 

Mmm, not sure I know which valve / mechanism you mean. There's a small cylinder type thing and another thing that's got what looks like a copper coil type thing fitted to it.


Which one do you mean ? I'll get the car up to temperature shortly and see what moves / doesn't move

 

the one with a Dome or 'cupula' nearest the top of the engine. It has a small rubber hose connected to a tube at the center of the dome. The one with the copper coiled tube is called the Expansion Valve and that one is for the air conditioner.

 

Thanks for that. Ok, tried it and nothing moves. Can the valve be repaired or will I have to get a new one ? Assuming this is the problem ?

 

Did you check it with someone else rotating the dial as you watched the valve mechanism? If yes and no response, the valve could be bad. There are other checks to make, how is the coolant level? Careful: do not open the coolant tank cap with a hot engine, wait until cold.

 

Check out my old thread. It wasn't quite the same issue, but it covers lots, and has heaps of advise, diagrams and articles that could be of use. https://www.jaguarforums.com/forum/x...nfused-139443/ Good luck

 

Four ideas:


1. If the "dome" has a pin arising from it's center, it is an original or OEM valve. It should move with the removal or application of vacuum.


Carefully, with the engine running, remove the vacuum hose. Moves?
Apply the vacuum hose, Moves? For clarity, a Mini Vac or other known vac hose would be best.


2. On LHD cars, like mine, there are two spigots under the battery for vacuum lines to enter the cabin and command the Dellanair. Missing or misconnected can do odd things. It is "touchy feeley" territory.
Fortunately, the spigots differ in size!!


3.Remove both hoses from the dome and splice them. Dellaniar gets heat, no matter what. Any change? Convicts or exonerates the dome?


4. Generic valves are available. Jut make sure the vac on/off logic is the same. My car has one and it works niftily.


Carl

 

Had almost the same issue and my small and a bit bigger hoses below the battery box were disconnected. The next issue I had was the check valve was stuck. Soaked it in hot water (suggested by Jose) and used a bit of air to unstick it. I had to jack up the car and slide under to investigate the two vacuum ports coming out of the firewall.

 

Yep, girlfriend was happy to twist my knob.
Coolant level is fine. I've disconnected the small vac pipe off the top of the dome thing but it's not made any difference.


This weekends tinkering project will be to take the valve assembly off and see if I can get it working. If not then i'll get a new one and hopefully this will fix it.....


I'll update this thread after the weekend.


Thanks to everyone for the guidance, especially you Jose. Much appreciated !

 

I don't like to throw new parts at the problem but sometimes parts substitution is needed to isolate the problem, and replacing the Heater Valve will be less money than replacing other parts like the Amplifier, which is the next check if a new Heater Valve does not resolve the problem. Removal of the Heater Valve requires pulling the fresh air Grille at the Cowl under the two windscreen wipers. Prying it always results in breaking it and scratching the paint. It is held in place by two Pins which are pushed into holes that are smaller than the pins. My solution is to slide a thin strap under the sides of the grille and carefully pull it.

 

Had a play around with the old valve and it isn't playing at all so have ordered a new one from SNG Barratt now. Fingers crossed it'll be the best £50 ive spent if I get decent heat on these frosty mornings !!!

 

ok, the heating will be good once the engine has reached its normal temperature and that is a function of the Engine's Thermostat. In my car, I added front seat Heating pads to the seat and back of each seat, it was not cheap or easy, but the result was very satisfying, since it does take a while for the 4.2 litre engine to warm up in cold weather.