Delanair MK II Climate Control--The basics
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Delanair MK II Climate Control--The basics
I've put together a short write-up on the Delanair MK II system which I hope some will find useful.
DELANAIR Mk II Climate Control
Series II and III Sedans
Early/mid year XJS
What follows is an abbreviated and somewhat random compilation of basic information that might be useful to those unfamiliar with the system.
System identification. The Mk II system was used on Series II and Series III XJ6/12 and early/mid XJS models. It was replaced by the Mk III system circa 1987 calendar year. The easiest way to distinguish between the two is the temperature control knob: the Mk III system has a “Pull For Manual Control” feature. The Mk II does not. The Mk III system was not used on any of the Series III 6 cylinder cars. The name “Delanair”, by the way, comes from “Delaney Gallay”, the company that manufactured the system.
Compressor. It is normal for the compressor to operate in all modes, even when heating is called for. The system is designed to refrigerate all incoming air first and then heat it as needed. This dehumidifies the air. The compressor itself is the common GM “A6 Axial Compressor”. The “Ranco Thermostat” cuts the compressor circuit if the evaporator ices up. Compressor protection was by a superheat switch and thermal fuse until circa late-1986 when the “HSLP” (high side, low pressure) circuit was used.
Amplifier. The amplifier is the brain of the system, located behind the console LH cheek panel. Roughly rectangular, about the size of a small pack of cigarettes, and has round multi-pin connector. The amplifier's job to process input from the control panel and temp sensors and 'amplify' the result to a 12v output to drive the servo. Some original amplifiers have be replaced with a round aftermarket type that looks like a shotgun shell. If replacement is needed it is common to leave the old amplifier in place as actual removal is tricky....so don't be surprised if you see two amplifiers.
Servo. Located behind the console RH cheek panel. The servo is the workhorse of the system that mechanically operates the vacuum valves, switches, flap linkages, etc. It makes a whirring noise when the dashboard controls are adjusted. When troubleshooting a fault turn the temp control knob and simply listen. Hearing the whir is a good sign. It means the system is fundamentally operational and is at least trying to comply with requests from the control panel. Lack of the whir sound means system is fundamentally inoperative. You can't go very far in diagnosing other problems unless you first hear the whir. The servo can be electrically divorced from the system for testing.
Fuses. This is the best place to start if you don't hear the servo whir and/or the blowers don't work. There are four fuses, two in the regular fuse panel and two semi-hidden inline fuses behind the console cheek panels. Behind the left cheek panel is a fuse on the amplifier ground wire. Behind the right cheek panel is a fuse clipped to the side of the heater case.
Amplifier failure. Historically, amplifier failure is much more common than servo failure, and most other failures....except perhaps heater valve failure. Failure modes vary from an outright inoperative system to erratic or non-logical operation. If it comes down to guesswork and/or no other definitive fault is identified, replacing the amplifier is a fair bet. Diagnosing other system faults is more difficult without a known-good amplifier.
Heater valve. The heater valve on the firewall is closed only when full cooling is called for. In all other circumstances it is open. Vacuum is applied to close the valve. Vacuum is removed to open the valve. Sometimes the valve is mechanically stuck and might be brought back to life by exercising the actuator arm. In other cases the actuator arm operates freely but the valve is broken internally.
Defrost mode. Defrost mode bypasses the 'automatic' aspect of the system and defaults to max fan speed and max heat. If you get max heat and blower speed then, at minimum, you know that A) the heater valve is open and B) the blower circuit is at least fundamentally operational.
Center dashboard vent. The center dashboard vent is designed to open only when max cooling is called for. When max heating is called for most of the output will come from the foot well vents in the cheek panels and a smaller amount from the left-right dash vents. In 'blend' or stabilized mode the output will be from both foot and left-right dash vents.
Face level adjustment. Later versions of the system have a hot-cold slide control under the radio. This is to adjust upper-vs-lower outlet temperatures. It is a very subtle trim adjustment. You won't feel a difference until/unless the system (and cabin temp) has fully stabilized.
Vacuum check valve. If the system misbehaves in accordance to throttle opening/closing and/or engine load, suspect a faulty check valve. It's the black/white plastic valve in the engine bay near the firewall.
Blowers. There are two blowers which themselves seldom fail. More common is a failure of the blower relay behind the console LH cheek panel. The highest blower speed is available under three conditions: when max cooling is called for, when 'defrost' is selected, or when the mode switch is set to 'high'.
Cheers
DD
DELANAIR Mk II Climate Control
Series II and III Sedans
Early/mid year XJS
What follows is an abbreviated and somewhat random compilation of basic information that might be useful to those unfamiliar with the system.
System identification. The Mk II system was used on Series II and Series III XJ6/12 and early/mid XJS models. It was replaced by the Mk III system circa 1987 calendar year. The easiest way to distinguish between the two is the temperature control knob: the Mk III system has a “Pull For Manual Control” feature. The Mk II does not. The Mk III system was not used on any of the Series III 6 cylinder cars. The name “Delanair”, by the way, comes from “Delaney Gallay”, the company that manufactured the system.
Compressor. It is normal for the compressor to operate in all modes, even when heating is called for. The system is designed to refrigerate all incoming air first and then heat it as needed. This dehumidifies the air. The compressor itself is the common GM “A6 Axial Compressor”. The “Ranco Thermostat” cuts the compressor circuit if the evaporator ices up. Compressor protection was by a superheat switch and thermal fuse until circa late-1986 when the “HSLP” (high side, low pressure) circuit was used.
Amplifier. The amplifier is the brain of the system, located behind the console LH cheek panel. Roughly rectangular, about the size of a small pack of cigarettes, and has round multi-pin connector. The amplifier's job to process input from the control panel and temp sensors and 'amplify' the result to a 12v output to drive the servo. Some original amplifiers have be replaced with a round aftermarket type that looks like a shotgun shell. If replacement is needed it is common to leave the old amplifier in place as actual removal is tricky....so don't be surprised if you see two amplifiers.
Servo. Located behind the console RH cheek panel. The servo is the workhorse of the system that mechanically operates the vacuum valves, switches, flap linkages, etc. It makes a whirring noise when the dashboard controls are adjusted. When troubleshooting a fault turn the temp control knob and simply listen. Hearing the whir is a good sign. It means the system is fundamentally operational and is at least trying to comply with requests from the control panel. Lack of the whir sound means system is fundamentally inoperative. You can't go very far in diagnosing other problems unless you first hear the whir. The servo can be electrically divorced from the system for testing.
Fuses. This is the best place to start if you don't hear the servo whir and/or the blowers don't work. There are four fuses, two in the regular fuse panel and two semi-hidden inline fuses behind the console cheek panels. Behind the left cheek panel is a fuse on the amplifier ground wire. Behind the right cheek panel is a fuse clipped to the side of the heater case.
Amplifier failure. Historically, amplifier failure is much more common than servo failure, and most other failures....except perhaps heater valve failure. Failure modes vary from an outright inoperative system to erratic or non-logical operation. If it comes down to guesswork and/or no other definitive fault is identified, replacing the amplifier is a fair bet. Diagnosing other system faults is more difficult without a known-good amplifier.
Heater valve. The heater valve on the firewall is closed only when full cooling is called for. In all other circumstances it is open. Vacuum is applied to close the valve. Vacuum is removed to open the valve. Sometimes the valve is mechanically stuck and might be brought back to life by exercising the actuator arm. In other cases the actuator arm operates freely but the valve is broken internally.
Defrost mode. Defrost mode bypasses the 'automatic' aspect of the system and defaults to max fan speed and max heat. If you get max heat and blower speed then, at minimum, you know that A) the heater valve is open and B) the blower circuit is at least fundamentally operational.
Center dashboard vent. The center dashboard vent is designed to open only when max cooling is called for. When max heating is called for most of the output will come from the foot well vents in the cheek panels and a smaller amount from the left-right dash vents. In 'blend' or stabilized mode the output will be from both foot and left-right dash vents.
Face level adjustment. Later versions of the system have a hot-cold slide control under the radio. This is to adjust upper-vs-lower outlet temperatures. It is a very subtle trim adjustment. You won't feel a difference until/unless the system (and cabin temp) has fully stabilized.
Vacuum check valve. If the system misbehaves in accordance to throttle opening/closing and/or engine load, suspect a faulty check valve. It's the black/white plastic valve in the engine bay near the firewall.
Blowers. There are two blowers which themselves seldom fail. More common is a failure of the blower relay behind the console LH cheek panel. The highest blower speed is available under three conditions: when max cooling is called for, when 'defrost' is selected, or when the mode switch is set to 'high'.
Cheers
DD
Hi Doug, thanks for taking the time to do such a great write up on this, I'm sure it'll be of use to many moving forward.
I also appreciate taking the time to give me a heads up and a chance to add to the "How to" section
It's now added to the "How to" thread for use by all
Thanks
Jim
I also appreciate taking the time to give me a heads up and a chance to add to the "How to" section
It's now added to the "How to" thread for use by all
Thanks
Jim
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From: Pacific Northwest USA
Here are some pics that might be helpful.
First is a diagram showing the approximate location of the amplifier, item #1 in the diagram
Next is a pic of the amplifier itself, so you'll know what you're looking for
Third is the servo....although, as installed on the car, it'll have a plastic shield covering up the mechanisms
Cheers
DD
First is a diagram showing the approximate location of the amplifier, item #1 in the diagram
Next is a pic of the amplifier itself, so you'll know what you're looking for
Third is the servo....although, as installed on the car, it'll have a plastic shield covering up the mechanisms
Cheers
DD
Last edited by Doug; Mar 12, 2017 at 11:18 AM.
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Joined: Sep 2016
Posts: 917
Likes: 389
From: VA
Doug, is the diagram roughly similar for the DelAir Mk III system? I was into one of the '89 junkyard XJS cars today and pulled all the fuses I could get my hands on as spares. Maybe a spare amplifier would be a good idea?
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The Mk III system is visually very similar in basic layout but the control system is quite different. In a nutshell the Mk II amplifier is replaced by an entirely different "Climate Control ECU" and the servo was replaced by individual motors to operate the flaps.
Some of the small vacuum valves and actuators, and other small parts, might be the same, I'm not sure.
Cheers
DD
Some of the small vacuum valves and actuators, and other small parts, might be the same, I'm not sure.
Cheers
DD
Junior Member
Joined: May 2020
Posts: 25
Likes: 3
From: Alberta
Good information. I have a 1989 xjs convertible with a totally dead climate control. it has the MK3 system and I am wondering if there are tests I can do to see if my problem is the ECU and then where do I find a replacement.
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https://www.jaguarforums.com/forum/x...-manual-83961/
Cheers
DD
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I suggest checking connectors as a preliminary step. I've fixed a couple Mk III systems by cleaning green gook of of the tiny connectors on either side of the main climate control case. They're easily recognizable because they're quite small with very thing wires. The tiny pins inside the connector bodies are easily compromised. There are 6-7 of 'em. One is hard to reach; left side, up quite high. Besides, any testing done with bad connections might well give false or confusing results
Cheers
DD