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I'm new to the XJS world and still learning but thought I'd stick my neck out and ask here what I'be been wondering about....Is the Delanair heading and cooling system worth the trouble to repair and keep working? Can and average sale tree mechanic do that properly?
I was speaking to a on owner recently of at least 5 XJS cars who told me that rather than try to fix and maintain the Delanair system I would be much better off just scraping it and installing an off the shelf conventional ac/heating unit...the type that is often times sold to be installed in cars that never had AC before (older cars, hot rods and such).
He made me wonder if there were better alternatives. Am I being too skeptical about a system I've yet to even see work yet? All I know is that it sure seems weird to me, for instance, to almost always require the A/C compressor to be running all of the time. I think I understand from my readings why they do that but is that good? Are there other car makers that do that or is Jaguar the only one?
Neither the Mk II or the later (around 87 and up) Mk III Delanair systems are that difficult to understand. The MkII is mostly electromechanical, and the MkIII is processor controlled. Factory information and user contributed information on how to diagnose and repair them is available. They don't seem to be much worse than other automatic systems of the period.
Wow, that is quite and undertaking to get that aftermarket unit in for sure!
Ok, it looks like I'd rather bite the bullet and get my MK II working even if it is piece by piece, bit by bit. I think I'm just overwhelmed with the thought of tackling it with barely any knowledge about it. I guess I'll learn :-)
Can and average sale tree mechanic do that properly?
Am I being too skeptical about a system I've yet to even see work yet?
The Delanair system can be a problem ...but not all of the problems are hard to fix.
All I know is that it sure seems weird to me, for instance, to almost always require the A/C compressor to be running all of the time.
That's to dehumidify the air. More comfortable and keeps the windows de-fogged !
For decades virtually all manufacturers have designed their systems so that the compressor runs in defrost or defog mode to help clear the glass. So there's that.
How many have systems designed to run the compressor in all modes? I dunno, but I'm sure Jaguar isn't alone. It's probably more common now than decades ago. What's different is that the older Jags didn't have an "economy" or "vent" mode to defeat the compressor if desired. I think Jaguar finally got around to that with the Mk IV system, or maybe the last of the MK III systems.
The mark II delanair system is pretty easy to fix, JagAire have all the main bits that are required to fix it, and it is a very powerful and reliable system once sorted.
I doubt you could get an aftermarket unit to fit and then you'd be lacking things like defrost. The Delanaire units work well, and between here and the suitable year XJ6/12 list on Jag-lovers there isn't anything unknown about them.
The mark II delanair system is pretty easy to fix, JagAire have all the main bits that are required to fix it, and it is a very powerful and reliable system once sorted.
I spent the winter of 2019-2020 working on mine and I'm so glad I took the time and trouble to do so, as it works better now than it ever did since I owned the car! I wanted the unit to cool as well as it did when it rolled off the line, and It Does!
As Greg mentions, Gary Crosby at Jag-Aire is *Very* helpful! It's almost like keeping these units working is his life's passion. He has testing procedures listed on his website, has new and refurbished components if you need them, and will "talk" you through if you have trouble.
The Delanair Mark II system isn't rocket science, merely requires methodical, step by step, logical work like anything else connected with a Jag.
(';')
The Delanair Mark II system isn't rocket science, merely requires methodical, step by step, logical work like anything else connected with a Jag.
(';')
Right !
I've had generally good luck repairing any faults that came along.
However......
Gah....unpleasant memory.....
There was one that drove me to madness and I was never able to figure out. This was in 2008 and I still wonder about it. It wasn't my car; it was an '86 that belonged to another fellow. If you changed any setting it would comply once....and remain at that setting. It would be totally non-responsive until/unless the system was turned off and then restarted. I eventually rigged-up a manual control toggle switch for the servo, akin to what Jagaire offers
That's my thread and "not for the faint of heart" is true. I enjoy wrenching, creating solutions, and making parts so it's in my wheelhouse. It's how I relax after a stressful day at work. The MkIII works good for what it is but I think I can improve it which is why I am doing it.
What are you seeing as the press for replacing the Delanair with the aftermarket one. (I admire your tackling of it as it requires a lot of work and planning).
My heater core started leaking this fall. When I started pricing heater cores all I was finding in stock were ones that cost $400. Coupled with the fact that a lot of other parts for the system are hard to find or completely unobtainable, I decided it made sense to replace it with a Vintage Air system while I was there.
I like that the Vintage Air unit doesn't run the AC all the time, and when it does run the AC, it only runs it enough to keep the car at the set temp. The Delenair system runs the AC to an evap temp of 38 degrees and adds heat to get the desired interior temp. I'm personally not a fan of that type arrangement.
To each their own and this will be invisible once the dash is back in place.
If any doubt the fastest way to differentiate is the MkIII system has a "Pull for manual control" function on the temp control dial. The MkII system does not.
The MK3 is not a horrible system, its actually pretty good. On the 94 XJS’, the AC is on even when you use heat only, because there is no on/off switch. So if the system has any door issues you will have diminished heat. With AC, the cool air can be heated via outside air going through the intake vents. If the System has a leak, the cold air will be diminished soon after a freon refill. The airflow system is always flowing when off, via vacuum especially if the windows are slightly open. This is a default setup due to English weather. Its designed to dry moisture thats dragged into the cabin via wet shoes. So if the stepper motor is open for heat, hot air will pull from through vents with the windows down. If you turn on the AC blower for a few seconds, the stepper will switch to cool air, shut off the Blower, and the air that comes out of the vents will be ambient air. Its a very confusing system, and it took me about 2 years of seasons to finally understand what works and what to expect. I say keep it and just use it as intended. If its setup decently you can freeze or cook
Just one question, you mention there is no on/off switch. But you can still run ventilation, heat, blowers etc without the aircon and compressor just by turning off the aircon with the little button top left of the controls, can't you?
Hey Paul. No I cannot shut off the compressor if the blower motor is on, whether its for heat or AC. I will be wiring one in soon. The only thing I can count on is suction pulling air through the vents with the windows cracked open, if the blower is off. One thing that used to annoy me was driving on a summer night and having hot air coming through the lower and upper vents with windows down, AC off. It would make the car not so easy to live with unless the AC was on. But if I turn on the AC with all settings to cold, the flap would open to fresh air, and block hot air from flowing. Once those settings were in effect(within seconds) I would simply shut off the AC and now fresh air will come through the vents. The flaps do have a tendency to default to heat if I shut the car off, sometimes no. So I felt heat coming through at any time, I would repeat the process.
Do you mean that the buttonstop left of the unit: "A/C ON" is not working properly? It should illuminate when pressed to indicate you're running the aircon circuits and compressor (irrespective of whether you want heat or cold). If you press it again, the light should extinguish and the compressor should not run.
If that's not happening, I would be examining the problem there, rather than try and fit an alternative on/off switch.
12-09-2021, 10:14 PM
Is the Delanair HVAC system worth keeping?
