Hello... my first post. 1991 xj6. working through issues with the delanair. Both fans work AC not working yet have to find the leak. No air comes out of the floor vents. The bottom vent motor moves and responds to changing temperature controls. Also heat comes out of face and side vents but does not change with changing the setting. It does not have a valve on the coolant supply to the heater. I read somewhere that some models did not have that feature. Main question is what controls air to the floor vents?

 

Hi sweetpeas,

Welcome to the Jaguar Forums! It's great to have you with us.

Please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

I am attaching some reference documents that may be helpful as you diagnose your Delanair IV system.

There may be some useful photos in the albums at these links:

https://www.jag-lovers.org/snaps/sna...?id=1390920386
https://www.jag-lovers.org/snaps/sna...?id=1390867076
https://www.jag-lovers.org/snaps/sna...?id=1390836244
https://www.jag-lovers.org/snaps/sna...?id=1390831473
https://www.jag-lovers.org/snaps/sna...?id=1390775046

My recollection is that the lower vents are controlled by the lower "blend flap," which is a rotating section of a "cylinder" or "drum," as shown from the right side in this diagram. The curved green lines represent the ends of the cylinder sections that rotate to open and close different ducts to direct airflow. The large blue rectangle is the A/C evaporator and the smaller blue rectangle is the heater core. You can see that all incoming air from the two opposing blower fans passes through the A/C evaporator, but the blend flaps determine how much air is directed through the heater core:



Regarding the heater water control valve, my recollection is that all XJ40s do have a heater control valve. On the pre-'93 cars, I believe it is mounted in the heater hoses near the left side firewall/bulkhead, tucked down under the intake manifold and, on left-hand drive vehicles, the brake actuator/reservoir (what is called the master cylinder on most cars). On pdf page 64 of the 1991 Electrical Guide, under Solenoid Valves, the valve for Coolant is shown in the upper center area of the schematic. You can download the guide at this link:

Jaguar XJ40 Electrical Guide 1991

It is possible that your 1991 did not have a heater valve, or that a previous owner deleted the coolant control valve, perhaps because it stuck closed during winter.

Cheers,

Don

 

Don the 91's eliminated the valve, re-introduced sometime later due to cooling inefficiencies I believe.

Larry

 

Thanks for the correction, Larry.

So on the '91s, the temperature is entirely regulated by the blend flaps restricting or enabling air flow through the heater core? This might support the theory that sweetpeas has an issue with one or both blend flaps.

 

Yes Don - some owners of cars without a valve clamp off the hot water line in summer. Fitting a valve would be a solution but a vacuum line would also have to be routed/fitted as that was also deleted on these cars.

Larry

 

Thank you for the replies. Found the upper blend flap motor missing! It is in a box of parts in the boot. Off to Iceland for a week and then into problem solving. The material you have sent me is amazing and I think the vacuum flap system is not operating correctly either. Previous owner said in 10 years he owned it the HVAC never worked correctly.

 

One reason to remove the upper blend flap motor would be to TRY and remedy the jamming of the upper blend door caused by one the demist flaps in the dash snapping and falling in to the heater. When this happens, it lodges itself in the upper door and prevents the door from moving.
The remedy is to remove the dash and repair the flap. The hack is to remove the flap using a long needle-nose pliers and wiggle the flap out through the centre vent. I have done both on my car as my dash-out repair failed after a year.

Larry

 

Thank you for the information. I'm now back from Iceland and ready to tackle my Delanair. The diagrams of the vacuum actuated flaps are most helpful. From all the information you have sent I now understand how it is all supposed to work. Will update my thread here with what I find.

 

Upper blend flap motor replaced and found a sock stuffed in the floor vents. Delanair now works and controls the temperature perfectly . One motor vacuum flap does not move but other than that it has transformed driving the car. Now to get the ac working. Thanks to you all for the information and advice. I also put Lucas steering rack sealer in, 2 bottles, as recommended by someone in the forum and the leak from the pump body O ring has stopped completely, at least for now.

 

Hello update on my battles with the Delanair system.Big step forward. There are small white cylinders in the vacuum lines under the dash. I removed the one to the fan vents and it was miraculous. Fan vents move in a few seconds and the whole system is fully functional. Not sure if they are filters or check valves but they were plugged.
Second discovery was that the relays for the AC fan and clutch had corroded terminals and although they sort of worked I replaced them and the relay sockets and power now reaches the clutch and the fan when I artificially send a signal.
Third discovery was the AC compressor seal was leaking. Found it by pressuring up the system with dry air. Removed the compressor and found a Chinese one yet to be installed for less than 300 canadian$. (hope it works). Also found it has the pressure switch and not the thermal link.
I am getting there and now know more about the delanair 4 than I wish I did.

Not sure if this is good practice but I used the hose and screw top from a recharge bottle and could cross thread the air hose into the screw top. It leaked a bit but I could pressure up the system and the leak was obvious at the compressor seal. I have a replacement drier bottle so hopefully this will be sufficient.