What does the a/c amplifier do in a series three xj6? Will the car still heat if it is disconnected ? ie remove fuse

 

The amp is the brains of the system. It compares actual temp to desired temp, "computes" an action, and from that commands the servo to open/close the various flaps and valves to give cooling or heat.

The system won't work without it

Without a servo "defrost" might work but that's it.

Using jumper wires you could manually control the servo to a medium temp/fan setting and just leave it there.

Or, using a couple relays and a toggle switch devise a manual control system to take the place of the amp

Cheers
DD

 

Thanks Doug. Could you please tell me where i can order a replacment amplifier? I have a 87 xj, and a 83 xj both with different "issues". I am away from the vehicles at this moment and will be for weeks to come. I do not want any jimmy rigging on the 83 xj so having the spare part is not an issue for in the event that the problem lies somewhere else. Also where can i find a hard copy factory manual for these cars? Your assistance is greatly appreciated.

 

Some info on manuals"
Books & Manuals


Rather rare multi-volume manul set:
1981 81 Jaguar XJ XJ6 XJ12 Series III Full Service Repair Manual 15 Volume Set | eBay
Although the listing mentions "1981" the basics remained the same through the entire Ser III run. A later version would be better as it would include the changes seen on later cars.



Condensed version:
Jaguar XJ6 XJ12 Repair Manual 79 80 81 82 83 84 85 86 87 3.4 4.2 5.3 series III | eBay
Edition 5 of this book is best but Edition 2 is most common and still very useful


Used version.
Jaguar Series III Factory Service Manual XJ XK V12 and I6 | eBay



Parts catalogs are very useful. Great illustrations
Jaguar XJ6 Series III Parts Manual/Catalog - Brand New! | eBay



I haven't bought a climate control amp in years so I'll let others chime in on the best sources

Cheers
DD

 

Thanks again Doug! I am living in yellowknife northwest territories and winter is coming fast!

 

I meant to say without a amplifier "defrost" might work but that's it.

Cheers
DD

 

I found some suppliers info for the amplifier on an old thread on this website from john's cars in texas i believe and caulfiedjags in australia. thanks to all to have contributed to this forum. I would post links if i knew how.

 

here's one way to post an active link:

1) go to the page you want to share, place the blinking cursor of the mouse at the beggining of the address of the page, for example: |http://www.*********.com by clicking the mouse there; (the address of the page where you are is always at the top address box of your browser, whether it is Internet Explorer, Firefox, Opera, or whatever browser you are using to navigate the internet).

2) once you are at the beginning of the address you want to copy, press the left button of the mouse, and keeping it pressed, move it to the end of the address to highlight the complete address;

3) then click the right button of the mouse and select COPY with the left mouse button;

3a) now you have the address copied in temporary memory; (also known as the Clipboard),

4) now go to the forum post where you want to share the link, click the left mouse button to select the place where you want to place the link, click the right mouse button, select PASTE with the left mouse button, and the link is pasted exactly where you placed the cursor.

NOTE: the link is kept in temporary memory, if you should turn the computer off, the link is erased from the clipboard.

 

My system blows warm air. My mechanic told me the compressor was
shot. I cleaned connections and it spins. we tried chargin the ac but their seemed to be a leak at least we think its a leak based on the gauge readout. Does this sound like a leak or could a faulty ac amp be the backbone of my system rejecting the attemped charging of it? I hope this makes sence...im typin while taking my pre jet football dump.

 

A faulty amp would not have any bearing on the *refrigeration* portion of the system. If the compressor clutch is engaging (and it sounds like it is since you say "it spins") but the system won't hold a charge then the amp is out of the picture.

Cheers
DD

 

and of course it could be a clogged Expansion Valve, a typical issue with these XJ systems, a cheap part but a PITA to replace since you can easily crack the evaporator brass line during replacement and then you might as well sell the car.

having said that, I prefer the expansion valve system to the modern orifice tube systems anyday.

 

Replacing the X-valve is very nerve wracking, yes :-). BTDT

Cheers
DD

 

Testing:Select 85 at the temperature selector switch. This will cause the relay in the amplifier unit to switch purple lead of the motor circuit to 12 volts. Red lead should reflect 0 volts.


After a few minutes, select 65 at temperature selector switch. This will cause the other amplifier relay to reflect 12 volts at the red lead and 0 volts at the purple lead.

If camshaft does not rotate in either test, check wiring continuity, FULL HEATING and FULL COOLING limit switches for continuity.

If correct, check Diodes (D1, D2 and D3) for continuity in forward and reverse bias modes.

If Correct:

1. Check that there are 12 volts at the brown lead and ground potential at the black lead.
2. Select Def. - Amplifier relay should show 12 volts at purple lead.
3. Check fuse in brown supply lead, 4. Replace amplifier.

 

I would trust the mechanic, the compressor Seals could be leaking especially if the compressor is an old unit;

if replacing the compressor, get the new lightweight redesigned version of the GM Harrison A6.
Save the old one to use as a core.

 

Hit the amp with a hammer, with the temperature selector set to the opposite of what the system is doing.. The relays go bad, or seize up, or just wear out and sometimes, this "old fashioned" method will get it working for a bit.. seriously.. also, rotate that white round slot in in the middle of the blue pot on the side of the amp a number of times to see if it makes any change.. These relays arent meant to last 30 years and are the source of a lot of problems.. also,, check those inline diodes on the servo unit harness,, I have seen five servo units and three of them had open diodes.. you can get the diodes at Radio Shack..

 

This is one I need to look into as well. Mine seems to be capable of performing every function but seems to prefer performing the function I least want at the given moment and doesn't seem to agree that I should be able to choose the function. 30 degrees F outside and you're freezing? AC on, blowing out the center vents no matter what temp is selected. Your bits turning soupy from the heat? Clearly, despite the dial being at 65 what you really wanted was full heat mode. AC is the most common, though, it's actually fairly reliable about giving me cold air if that's what I'm after. It doesn't like to give heat, it seems to get stuck in cold air mode. I put in a different, used, unknown condition amp and seem to get pretty much the same results. I thought I had something when I adjusted the screw on the amp most all the way to the right and it started giving heat but then a few days later it refused to give heat again. Going to have to check some of those diodes and see what the amp is actually requesting. I suppose it could be a servo issue but I don't think it is just by the way it's acting. Particularly getting the max cold fan speed while heat is selected. More than likely it's multiple issues compounding themselves making diagnosis a pita.


Edit: I should clarify 99% of the time if I want AC it will give it to me, just doesn't seem to want to switch to heating mode and I don't think it's the heater valve. When it won't blow hot everything, from fan speed to vent selection to air temp, is stuck on cooling mode. On the days when the servo decides to move and switch to heat mode the air is always warm. Even when it does switch to heat mode it seems to do so only at the lowest fan speed. Every once in awhile it will give me good hot air movement with the dial on 85 and defrost selected. All this is true regardless of which mode is selected, low, high, auto, ect. Even with the temp dial at 85 it will usually switch the compressor on and blow cold in all 4 fan modes, except on those random days when it decides to cooperate and give me heat.

 

Very possible.

I must say, though, that what you've described has "bad amplifier" written all over it. Wish there was some way to guarantee I was right...but we both know I can't

It takes a lot of patience to check out the temp sensors, connections, vacuum system etc. You can spend hours on this (I have) and it can be doubly difficult without a "known good" amplifier.

Oh....forgot something....

One time (I'll keep this short....not easy when discussing Delanair climate control) I was suffering from erratic/lazy/slow temperature regulation the the problem was the the tube from the cabin temp sensor had fallen off. It only takes 15 minutes to remove the upper dash pad to inspect for this. With the tube off there was no cabin air being drawn over the sensor.



Cheers
DD

 

My SII has the complicated Jag climate control AC/heating system (as compared to the manual separate systems of my Series 1 cars).

Finally found a local foreign car parts shop that had the correct sized rubber hoses for all the vacuum lines. Now they do not fall off....

 

BTW, the "Delanair Training Manual" is worth every penny:


Click here and scroll down a bit

Jaguar Books & Manuals | Jaguar Parts Manual


Cheers
DD

 

I'll check the tube, Doug, thanks. The main reason I had started to think it might be something other than the amp is when I installed the junk yard amp it acted exactly like it did before replacing it. When they fail is it usually heat they don't want to provide or was mine simply a coincidence? Maybe it's because I've seen too many episodes of NCIS but I tend to shy away from believing in coincidences.