Tonight I undressed myself and walked naked in the night, I saw red stars falling, and I saw burned towns, and I saw crouds of people…
Marek, my guess is - you have 17th Edition and dozen of refreshers. So in other words - capacitor inside of transistor housing ?
I’m not sure I understand any of that.
If the small capacitor in the circuit I posted fails, then the transistor can never conduct. What appears to be happening in your case is that the transistor always conducts 100%, i.e. the switching transistor is bad because it is not accepting the control signal. You need to sketch out the circuit and all will become clear.
A transistor is a “current multiplier”. It switches on when it isw passed a small control current through its base (“B”) terminal and this allows a larger current to flow between the “C” and “E” terminals. The little capacitor is in the “B” leg of the circuit, so it has to be charged up by the low current control signal - this means the main circuit only turns on in proportion to how the small circuit turns on.
kind regards
Marek
Oj Marek Marek…
Let’s try to recall some images from post-mortem:
Going by the probability calculation - it means that each capacitor/transistor (out of four blowers) is busted… Everything is possible with British automotive, however blower motors are also fused with 25amp /each. Let’s try to re-word it:
In well-working AC system - does anyone ever experienced "click!-k!!” while truning the knob from off to low??? This sound is still present even with both fuses off.
My Jag (1989) has nothing like that (blowers going on silently) while the Jag in interest of this topic is doing so… The plan is to trace the sound to the source…
Also, AC compressor electromagnet was disconnected as a first thing to check…
I see you rusted the interior to much the rest of the car? 
Four blowers?
Why do I think there are only two?
Yes, there is a click when turning the knob, even with the ignition off. I guess it must be the micro-switches behind.
It is possible that the click is the high speed relay on each blower; something engaging relay immediately with key on- this would cause large draw on start (50a). Relay is fed from an always hot brown wire if I recall, don’t think the 25a blower fuse prevents high speed but am not sure. If so, than problem is on the control side of relay (module?), otherwise blower would stay on with key off.
So far I can see one very rusty transistor, probably two resistors and a small diode of some sorts. It’d help to know what the writing is on these components and how they are connected.
Perhaps someone with a working example can contribute.
kind regards
Marek
Thank you Kirby.
That appears to cover off everything you’d ever want to know about the circuit.
kind regards
Marek
EDIT - spray the newly constructed board with lacquer so it won’t rust up and short out like the last one did. If you really want, mount the big transistor on a heat sink.
Two pairs of the blowers were tested with one AC module - hence total number of 4.
Rusty photo above was taken during destructive disassembly of the blower. Or rather what was left from it.
Indeed the sound belongs to high speed relay which is hot wired regardless of the fuse status. It is loid as the flaps are jammed half-open 
Both blowers are actually starting for 2-3 seconds, then being disconnected by AC module I guess…
In the same time, with engine warm (heater matrix warm?) - everything goes back to normal after few minutes run on high speed (no fault, all speeds back, with temp sensors disconnected/connected = no difference)
Without semantics - it does look like AC module fault. To be confirmed shortly via quick module swap.
My ‘88 has a functional system (as far as I know), and I have observed the same “high blower for a second or two” on start, but only occasionally; seems to happen when system was in high blower cooling mode on shut down. May be normal under those conditions…
Mine seems to have a temp overshoot issue, cooling on restart when not necessary- I understand that Jaguar corrected in later models by using a in-car sensor with a fan.
