Looking at the clever schematic I noted the same thing about the switch, about the NC situation.
Indeed, this is my situation:
On yesterday tests I measured the clutch inputs and I detected no 12v all the time (except when it engaged, but I wasn’t measuring). I think to start to check the continuity all back to the relay.
No good news: some PO touched the system.
This is what I found:
That black cable goes to the rh to this fuse:
Now everything gets more complicated. The cable out of the fuse is a GN cable, Inwill test if it goes to the clutch. The rest of the system seems dead, no servo sound, just blowers sending hot air from the vents except the central one. The DEF position continues to work.
Anyone has an idea about that bypass? Why?
P.S.: I checked all the fuses and all the values on the round connector, all values are ok except from the 30-100 ohms to be found between purple and red, where it seems to be an open circuit.
Patrizio,
Prior Owners and their shops know no bounds in their creativity when it comes to modifications and repairs.
I have never seen that wiring modification before but some of my Jaguars had jumbled up messes of wires due to Prior Owner “repairs”. The only advice I have to offer is for you to return the wiring to the factory configuration first before proceeding any further.
Green wire with a Brown trace is normally used for the A/C compressor clutch. There is no certainty that the person who did that modification adhered to that convention.
Paul
Patrizio,
Red and Purple wires from the amplifier harness are used to drive the servo motor. Both wires have a normal state going to ground. When the temperature sensors become imbalanced…the amplifier switches one wire to positive…which drives the servo in one direction or another depending which wire is switched hot ( red or purple)
It appears some previous owner has spliced into the red wire. Without a bit more information to clarify…this arrangement may force the servo to one of its limit switches and hold it there.
I recommend disconnecting the splice, then disconnect the amplifier plug (white octagonal plug) and proceed testing the servo…
I recommend a 9 volt battery with a set of snap on leads. On the female plug socket…provide + to Red and - to purple…listen for the servo to whir. Now switch polarity…-to Red and + to Purple. Listen for whir of servo. If servo fails to move…a faulty servo motor is suspect.
Next check the servo feedback potentiometer by connecting an Ohm meter (digital volt meter) to Orange and Green while running servo to its limit switches. 2 KΩ for max cool and ~0Ω max heat. You also want to see a nice smoothe increase and decrease in Ω’s. Any drop outs other than about 400 Ω (meter switching auto range settings ) indicate a bad or dirty feedback pot.
Once we know the servo is working we can then work on correcting the AC compressor wiring. And then finally ruling out a faulty amplifier.
Hope that helps…
Gary
Thanks again to everyone. I will proceed to test according to @Gary_Crosby indications.
I’ve studied the Delanair Climate Control Manual and my suspect is that is an “economy” modification: the red wire carries current to the servo when cooling is required, so the clutch is driven only in this situation and the compressor remains off otherwise. I guess that the red wire continues to carry current to the servo in maximum cooling mode thanks to the free-wheeling diode, so it could be that in maximum cooling according to the genius that made this modification the ac stays on.
It’s a big amount of suppositions but it has a logic: if the amplifier is broken as I suspect, the inconsistent behaviour of the clutch is related to the inconsistent functioning of the amplifier itself.
I will try to take the wiring back to the original layout, hoping to understand where that poor GN cable was connected when new…
**
The thermal fuse itself normal screwed on a bracket on the compressor, Patrizio - the fuse is connected to the wires by a connector with three wires. Your last picture shows only two wires on the connector…?
The green/brown wire is powered via the Ranco thermostat (on the evaporator) with ign ‘on’ and the selector out of ‘off’ - unless the Ranco temp is below +2C (when Ranco interrupts clutch power). The wire from the thermal fuse to the compressor clutch is (originally) green - connected to green/brown inside the thermal fuse…
As the clutch (when the thermal fuse is fitted), is permanently grounded (black wire); the standard clutch test is to apply 12V to the green clutch connector - the clutch should invariably engage. Does it…? And if not; does it engage if the black clutch wire is simultaneously grounded…? Seemingly; a PO has bastardized the thermal fuse/connector - and it is essential to verify that the clutch itself actually works.
You may have two issues; one relating to the thermal fuse/clutch power feed modifications - and one related to the servo/amplifier. The latter to be tested as described by Gary…
However; it is very(!) important to bear in mind how the system is meant to function. Cabin temps are set by flap positions and fan speeds - which are set by the servo, as directed by the AC amp.
Ie; the compressor, when ‘on’, is always running the evaporator at max cooling. The heater, when air heating is required, is always at full heat (heater valve open). The system runs full cold or hot to quickly reach the set cabin temps - air (always going first through the evaporator) is either passed though the heater core, or the heater core is bypassed - either done by flap settings…
Obviously, if heater core is cold or evaporator is not cooled by compressor - the systems range of heating or cooling is restricted to ambient air temps. In such cases a working AC amp/servo will go through the motions; setting flaps for the intended effects - but with limited capacity for cabin heating or cooling…
However, if the AC amp fails; system sticks in one position; from full cold to full heat - or anything in between. Or occasionally; a failing AC amp may randomly alter servo positions giving bewildering temp changes. All the above is why verifying AC amp function is essential - to search for component faults with a faulty AC amp is futile…
The system is basically slow reacting; resetting servo may take more than half a minute - and of course; getting the heater hot and the evaporator cold is no instantaneous.
In your case (crudely); if the centre vents stay closed - the system is in heating mode. This can only be rectified by moving the servo - air flow is passing though the heater core, and air flow temp is a function of heater core temp…
As the AC amp relies on the in-car temp sensor; it is advisable to verify cabin temp with a thermometer. The AC amp will select servo position based on this - it basically compares resistances in the in-car temp sensor and the temp selector. Then turns the servo to eliminate the difference between the two by resetting flap positions etc…
Frank
xj6 85 Sov Europe (UK/NZ)
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Patrizio,
adding to what Paul wrote: re-inventing what a PO or his mechanic thought or did when rewiring entire parts of the car is near impossible. Your only chance is to track every single wire to its connections and re-fabricate a wiring pattern.
I’d follow Paul’s advice and simply tear out everything that’s neither original nor identifiable. To identify original wires make use of the famous S57 wiring pattern for SIII cars - maybe there is a separate pattern for the AC. From your pics I’d guess that the fuse holder for the blue flat plastic fuse is not original and also the wires going in seem to be fabricated - guessing from the insulating tape at the connectors. In the picture before the connection of the red and black wire looks more than suspicious for me while the white fuse holder could be original.
With the wrong wires out and a correct wiring pattern it should be no big deal to fabricate - and document - new wiring (ideally in correct colours).
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
I too have been pretty well frustrated with the endless difficulties getting a reliable heater in the cold times, and a/c on hot days. After following this thread for a while now, I got off my duff and ordered a ‘manual’ control for the Delanair MKII system. A few days ago I was telling my wife how much I would like the XJ’s system to be manually controllable. I managed to find just such a control switch while surfing the net to find a new, aftermarket a/c amplifier. Check the web site: Jag-Aire.com (I have no affiliation with them) to look at their amplifier, and/or their ‘manual’ control. I ordered the manual control, which is supposed to bypass the amplifier. I hope it will be the solution I am looking for. My unit is in the mail currently (I just ordered it yesterday)
A properly functioning Dalanair II system works very well and needs only minimum input from the driver.
When I first got my car I also had the same thoughts, but now that is working as it should I really love it.
It was a long and arduous process though…
Aristides
I have a quite clear idea of the modification that has been carried out. I will take this week-end to strip It down (and to mount this NOS baby).
I will keep the thread updated asap.
**
The manual control only overrides the AC amp control of the servo, Kassaq - it still requires the system to work properly…
Frank
xj6 85 Sov Europe (UK/NZ)
**
That sounds good, Patrizio.
And the Nakamichi RC head unit is somehow close in appearance to the stock Alpine 8600
Keep on digging
Jochen
75 XJ6L 4.2 auto (UK spec)
Yes, excellent quality and the right style, I tried to find the original but with no luck. I got a little mad in installing and fitting inside the dashboard, I hope I didn’t damage anything at the bottom of the compartment.
Just perfect - guess the LED lights are green as well!
Out of curiosity - did you really try a tape in it, and, if so, with what result?
Best
Jochen
Incredibly good, tbh. I tried an original cassette from 1996 and I swear if I didn’t know it was a cassette I could say it was a compact disk, despite the 32 y.o. speakers (that are very good as well).
Ok, I think we are at the end of the journey.
First: I attached the GN wire to the original loom (coming from the Ranco), the a**#ole that made the modification cut the wire attached to the connector (no comment) so I had to make a new connector.
This is the final work, not what I hoped but the best I could do:
Then I tested at the Ac amp connector all the values again:
blue to white: correct, 9.47 Kohm at 65 and 0 at 85
blue to brown: almost correct, detected from 9 to 7.5 kOhm that should be good for today (28-30 °C)
orange to yellow: 2 kOhm constant, ok
orange to green: 2 kOhm, the system is stuck to full-heating
purple to red: document says that it should be 100 Ohm but I found 1 MOhm, so I proceeded to test the servo using a stabilized power supply (I tried the 9V battery but the response was way too slow)
Using 12 V red to purple (cooling direction), the servo happily moved with a maximum current absorption of 0.1A, I think it’s acceptable but please confirm. After the servo stopped moving, I tested again the orange to green finding a good 0 Ohm as expected.
Then I started the car again, in AUTO mode I had about 5 seconds of full blowers from all the vents but immediately the servo started to work and took back the system in full-heating mode.
Now: is this an unequivocal sign of a broken amplifier or there is some sensor I am missing that can force this behaviour?
As always, thanks for the support.
If:
then 100% you need a new AC Amp.
Best,
Aristides
Hi Aristides, thanks! I will proceed in buying another amp (fingers crossed).
Looking at it, it seems the brown one and quite impossible to take off without dismounting a lot.
Yes you need to dismount some…
But if you get the little bullet Amp, and if you don’t want to bother, you can just leave it there and mount the new Amp somewhere close by.
Aristides
Based upon your findings of sensor values, and your correction of PO modifications to the wiring…i would be confident your amplifier has failed.
You can leave your original amp in place and simply tuck the replacement behind the vent cheek panel.
Cheers
Gary
