I have been given a used after market a/c amplifier the small tubular one's
will it need adjusting, at the moment it is set to almost full negative but I don't know what the + and - actually mean, has anyone else fitted one of these and did you adjust it at all, were there instructions with it?
or anyone tried this alternative
https://www.jag-aire.com/copy-of-ja-16-details-1

 

Rex
The "shot gun cartridge" type are pretty reliable. Turning the adjuster clockwise means MORE cooling at a given dashboard temp setting. Anticlockwise means less. What I did was to turn it to half way, fit it so I could easily get to the adjuster, then warm the car up, aircon on. Once all up to temp with the dash temp knob set to my normal 70, I then adjusted the amp adjuster so it kicked in about right to give me the temp I normally have.
You can easily hear and feel the unit responding as you turn the amp adjuster one way or the other.
The JagAire stuff is very good and a friend has had one of his rebuilt amps and it is fine, as is his rebuilt servo unit. He also sells a rocker switch that gets rid of the amp and allows full manual control of the temp. The switch fits into an ashtray and works well too.

 

That looks to be a very handy gadget. If I'm reading this correctly? The actual amplifier allows you to adjust the A/C system to a lower setting, then the dash setting shows?

And the bypass, allows you to have full manual control, of the system? So that gives us 2 different ways, to lower the A/C setting. Did I get it, or a'm I still lost. Thanks

Jack

 

Or higher setting.

This is a calibration type thing.

For example, if you set the temp control to 75 but the system wants to keep the cabin at 70 or 80, you'd use the amplifier adjustment to make the correction. After that you'd forget about it entirely, probably for the life of the car unless something in the system degrades in some way



The bypass eliminates the amplifier and thus eliminates automatic temp control, yes. A manually operated "colder-hotter" switch is used to adjust the system to provide cooling, heating, or blending. So, rather than a solid state brain issuing orders to the servo, a manually operated switch gives the orders.

However, the system still uses the servo....which controls fan speed and which outlets the air comes from.

Cheers
DD

 

while on the subject of aircon has any one had suspicions that the plastic heater valve, mushroom shaped after market ones, may be leaking I put a pair of mole grips on the in pipe to shut the water off and the air seemed cooler, also has anyone noticed that pollen filters restrict air flow at all.

 

Assuming it is the same as an OEM one, the valve is normally open and only shuts when full cold is selected on the LHS temp control knob. In really hot countries, or seasons, when warmth is not required, blocking off the valve will reduce the effort of the aircon to maintain a cool cabin - but you will not be able to heat it al all. You may well have mimicked this with the mole grips. Also, the air blend design does rely on good sealing within the unit, and ours being old, are probably not as good as they were.
I have always though a cabin switchable electric valve would be a good idea. They do exist.

 

Any heater valve can degrade and fail to open or close completely...typically from clogging, corrosion, and/or or the internal seals failing


If clogged they surely will

I've never seen an XJS with filters fitted although Jaguar did offer them for awhile....perhaps still. The part numbers are out there somewhere.

I always felt the air flow on my XJS was a bit on the weak side even without additional filters and with everything working as it should. I'd be reluctant to add any potential restrictions...but that's just me

Cheers
DD

 

Thanks Doug I was pretty sure I was on the right track. I'm a very good Mechanic/Technician. But when it comes to electronics??? I like to put it this way. Electricity is simple, 2 wires from point A to point B, no damage, or breaks in the wires, all is good! Until you throw in that little BLACK BOX!!! Then all bets are off! Cause that little sucker can, and will send power, anywhere it feels like it, and drive you nuts trying to figure out, what the HE Double Hockey Sticks happened! Case in point I had a School bus with the 8 way warning lights (the ones at the top, Red and Yellow) going haywire. They would just go nuts, sometimes they worked, or half would work, then only 1 would flash erratically. I'm thinking, "Christine Sh-t"! I worked on it for a week, checked, and unhooked, everything that had anything to do with the system, still no help. So I called the Bus guys who built the dang thing and said what the &^$$^&%$ is going on!!! Kent Pascoe says go unplug the "Bumper Magnet" for the Crossing arm on the front Bumper, He said it's shorted out, and back feeing into the 8 way system. I said you've got to be Kidding Me! He said you think that's bad, you should have been the first one to find it!!! He said it took us 3 weeks!

Jack