Hi all,

I have an XJS Convertible. I had the AC repaired to the tune of $1,300 as summer and it worked great

Since the cold weather has started I am only getting cold air even though I have the system set for heat. I replaced a fuse and the heat started working better.

I am getting heat in the footwells, but still only cold air in the center vents. I looked around the system today, but can't see anything disconnected.

Any thoughts???

Tony

 

Going to be blender door problems. I don't know if the later years have other configuration, but i know pre-facelift you basically just get air jetting out everywhere.

I have never dug into it on my car, nor seen any diagrams, so you will have to wait for someone with some more under dash familiarity.

They are always similar though, I believe access is on the passengers side, but not sure. If you remove the glove box and all that junk and I think you have access to the linkages. From there you should be able to switch from HEAT to COLD and see if everything is moving. A bit of thinking should tell you where everything should be moving and what flaps it may lend to.

 

Which year and model do you have? Did you know there is a quadrant/slide control under the centre of the radio, maybe slide this towards the red up arrow, if it is not there at the moment?

Greg

 

Tony,

As mentioned, your signature doesn't indicate what type of XJS you have. But if you have a late XJS, then the centre vents do not provide direct heat, irrespective of the temperature setting. Even if the slider control is set to the blue side, it merely enables the centre vents to provide a slightly lower temperature than that provided through the foot vents.

If you read through the drivers handbook, it will explain that the centre vents don't provide heat.

As I said, this relates to the late XJS system.

Paul

 

Wouldn't that be because the foot vents get the heat first, so it will always be less than them? It is still be directed through them, so it is still heat right? Are you sure the manual doesn't mean they can't solely provide heat?

 

On the older Delanair II and III systems the *center* dashboard vent is supposed to have air flow only when *cold* air is called for.

If heating is called for the airflow will be mostly footwell vents and some R/L upper vents (but not center vent).

If blending/medium air is called for most the air flow will be the R/L upper vents (but not center vent) and a bit to the footwell vents

Cheers
DD

 

sidescrollin,

As Doug has said for the Delanair MkIII, on the last XJS system, the centre dash vents don't provide hot air.

You can get a tiny bit quickly as you change the settings, but only until it's changed the flaps and sent it as per the handbook describes.

Paul

 

I remember during the mid 90s when I owned a BMW, the owners manual said heat would not come from the upper center vents for safety reasons. Something about blowing hot air into your face and how that could be potentially harmful/dangerous.

 

Hi all,

My XJS is a 90 convertible V12. I took the access panels off both sides and unplugged and plugged connectors both electronic and vacuum today. The switches that open/close vacuum valves seem to be working and I could feel vacuum in various positions.

I did manage to get the demister (defrost) setting to generate lots of hot air to the windshield, but other than a bit of heat as the system was resetting flaps, the foot wells and only generated cool air.

I read the manual and understand that the center vents only do cool air. Gosh that was a dumb thing to do. Anyone know what the logic behind that was???

Last winter I only got heat via the defroster. I'd like to figure out what is the issue so that my feet get warm on these cold NM mornings.

Thanks,

Tony in NM

 

BTW I think the 90 XJS has the Delenair Mark III system on it as the temps are controlled by electronic means as opposed to direct turning of **** (which I think is the better way).

Tony

 

Call me old fashion but I want the vents to do what I want them to do when I do it.
Give me the old manual controls that works so well in almost every other car.

 

Forgot to mention. Check the vacuum line on middle of firewall. I replaced mine and flaps started working

 

I agree about the manual controls. I don't understand when something works flawlessly they fix it with something that sucks.

Tony

 

Actually there is nothing 'manual' or 'direct' operating on either the Mk II or Mk III system. In either case the control knobs simply telegraph the driver's wishes to something else.

On the Mk II system the knobs control a relay pack, and send a signal to the amplifier....which in turn operates the servo....which in turn operates the flaps and switches to control air flow and temp.

On the Mk III system, in a very brief nutshell, the amplifier and servo are replaced by an ECU.

Cheers
DD

 

dtony, Although you may not have intended t do so, you said something quite humorous when you said the new systems suck. Indeed they do, in more ways than one.
RagJag.

 

DD, I realize that the MKIII is electronic in its connections. My reference was to some of my former and current american cars that have a lever which has a cable that moves things around. From my exploratory surgery this past week, I saw that the **** and were linked by wires to the servos.

I once owned an 89 Lincoln Continental with a electric blend door actuator. That thing stopped working one winter so come the following Spring, I only had heat. That was really the pits as that was a great car otherwise.

Ragjag, I got the joke of what I was saying as part of my explorations was trying to find rather the vacuum connections were all sucking as they should.

A guy a went to graduate school with posted on face book last week that he (really living on the edge) was visiting the vacuum cleaner museum in Kasnas City, Mo. I posted that I bet that really sucked.



Tony

 

OK, so yesterday I fooled around with the XJS's heater system for several hours and don't feel like I got anything done. I drove the car to church this morning (about a 20 min drive from where I live) the heater worked great!!!!! I have no idea why however.

After church, I drove it out just outside of Albuquerque to a casino for lunch with friends. The heater only blew out cold air. When I set the defroster, the heat coming out the top was hot, but still cold at the footwells.

Tony

 

The last three days have been,

in the early AM, the heater works great. By midday (12PM -2:30) the heater only blows cold air. After dark, the heater runs perfect again.

Any ideas??

Tony

 

Tony, There is a cabin temp sensor, an aircon evaporator temp sensor, and a temp selector knob. The 'ECU of the D MkIII takes these inputs and issues commands to the flaps, aircon compressor etc. One or more of these items is not working properly, a matter of electronics I am afraid. You need to find someone who knows how to test them. I cannot help with that, sorry.

Greg