Just in case anyone is wondering what they look like, here's the servo form a Delanair Mk II Climate control system used on Series II and Series III cars. The only exception is the V12 Series IIIs built after August 1986 which had the Mk III system.

Anyhow......

It's really a fascinating contraption. I hate think what it must've cost to manufacture them back in the day.

In a nutshell, a small reversible motor (commanded by the amplifier) drives an axle shaft. Cams on the axle operate micro switches and vacuum valves, and gear driven arms operate the linkages and bell cranks on the RH side of the climate control case....which in turn open/close various flaps.

Cheers
DD

 

Good grief Doug, that brings back nightmares.

Cost????, I would not go there at all, would have been HUGE.

It is a clever little thing all the same.

 

Would make Rube Goldberg proud!

 

Indeed!

Amazingly they don't give much trouble.

If Delanair could've done as well with the notoriously troublesome 'amplifier' many owners would be much happier!

Cheers
DD

 

The electro mechanical art at it's best.




AS I "understand" it, the workings of the amplifier are encapsulated, and thusly hidden from view and illustration. Too bad, it woulds vbe interesting...


Carl

 

I've been told Series 2 has no amplifier. Was I misinformed?
(';')

 

Yes.

The amplifier is the brains of the whole shebang.

The Ser II and Series III are virtually identical as far as climate control.

Cheers
DD

 

is this essentially a mechanical relay and motor for the flaps in one? I am constantly amazed at the complexity of my car.

 

Yes! It's a wonder Anything in the climate control system works at all, let alone how well it usually does!
(';')

 

it does work well when it works. i have ice cold air from the center vents and very hot heat from the lower--unfortunately at the same time right now, but there are enough step-by-steps on the forum that i'll start tackling that soon. i wonder if we could remove everything and hard-wire fan on/off, heat hot/ac cold through all vents.

 

Agreed !



If there's a will, there's a way.

One time, facing a system that was defying all diagnosis, I wired-in a toggle switch to drive the servo, thus turning it into semi- manual control system. With thought and effort I'm sure all the functions could be rigged to manual control.

Frankly I've long felt that fully automatic systems are a needless complication. Even on a 'luxury' car I wouldn't find it to be such an oh-so-terrible discomfort or hardship to....oh my gawd!.... MANUALLY set the controls to my liking and adjust them from time to time as conditions change.

Cheers
DD

 

my '84 still runs on the one it had in 1989 when I bought the car, never an issue with it, maybe because of the John Egan Quality-Or-Else days?? I have another one from a 1986 XJ-S V12 Coupe just in case.

 

As I mentioned earlier they are surprisingly trouble free so I'm not surprised that you haven't had any trouble. It was something that Egan didn't need to fix. And, since the servo wasn't manufactured by Jaguar anyway, he might've decided to just leave well enough alone . Too bad they left the troublesome amplifiers alone, though!

Cheers
DD

 

Doug, that's Heresy!
But I agree.
(';')

 

Ok so the supply of amplifiers is now exhausted, someone needs to slice one in two and find out what is in there!

 

My Jeep has the simpler HVAC. Shared by a lot of cars, I think.
Dial one way into the blue zone for cold. Dial the other way into the
red zone for heat. Another knob to select fan speeds. The latter
by introducing resisitors of various values. Hi only at present. No problem, just use the vent selection control. Deflect full cold to the windshield and let it cool that way.


A Deluxe version is referred to in my manual. Full climate Control ala Jaguar.


The word amplifier suggest it intensifies signals from the sensors so that the rotary device can arrange the mechanics to cool or heat.


Slick, I think.


So, toggle full heat or full cold. Toggle all to defrost vents. Select fan speed. Driver in control....


Carl

 

I have an xj6 series III. I have a situation in which if the Temp control dial on the left is rotated towards heat, (that is anything hotter than 70), the motor will turn the gears in the servo a fraction then back rocking back and forth in a loop. it reminds me of a garage door hitting an obstruction and then trying over and over. I have loosened the pull rods thinking they or the vent might be frozen. They are not frozen and open and close their respective vents against only spring tension. Has anyone experienced this? would the amplifier cause this kind of behavior? I fear something frozen in the gears or a jam but I do not know how to go about getting into the servo to see if a cam is stuck or a piece of plastic or something has wedged into the gears. It seems unlikely. I began to wonder if a faulty amplifier could be the cause. I know nothing about what an amplifier is or does and have only recently read about them. The car sat in a hot humid Houston garage for 6 years.( I have already re-soldered 2 relays for that tiny hair this wire to the post) The low setting on the fan has ceased to work, in that position and all the rest the servo will begin its rocking. I was alerted to it because i could hear the servo motor rocking in the low position for lack of fan noise! I see that the vacuum heater valve is corroded into "off " as well. Any help will be much appreciated.

 

watch the heater valve after the engine has warmed up to Normal Temp.

with someone else in the car and you looking at the heater valve, turn the heater ON, TEMP to 85 and Mode to AUTO.

Can you see the heater valve linkage moving ?

if the heater valve is corroded into OFF, the heater is not going to work. What may be happening is that the Servo is trying to "settle" into the Heat Mode and the Heater Valve does not let it.

 

I just applied power to the red and then purple leads. Full travel achieved with no binding. I guess the amplifier is giving an oscillating polarity signal. Is there a test for the amplifier? Would the temp sensor possibly be to blame?

 

Thanks for the idea Jose, I was thinking along similar lines. The valve is definitely corroded and binds. As a test, I moved it to heat position and a few places between, and the oscillating back and forth of the servo does not stop. I will however replace the valve and try again!