Happy New Year, everyone.

To start the new year off on the wrong note, once again an issue with Her Ladyship rears its ugly head.
This morning, after a 90-min drive in the rain the previous evening, the battery was flat. Got that fixed, and found that the culprit was that the aircon unit does not switch off when the ignition is off. I've pulled the negative terminal so it will stop, but obviously it needs fixing.
The air conditioner itself seems to work fine--blows cold air when set to cold, hot air when set to hot. But turning it off, there's no sound of movement (I had to delete a vacuum resistor that slowed the flap, as it had failed, so now the flap shuts quickly, with an audible snap), and the motor keeps going. Even with car off and ignition out. However, when I turn the aircon "on" from the off position, there is the initial roar of air/motor as it spins up.
There is a gentle warm breeze from the right-hand side vent, a zephyr from the top vents, nothing I can detected from the left-hand side vent, nothing much from the footwells, and maybe a warmth from the rear.

I have read a post HERE where JagBoi says "It's probably more likely the Darlington transistor on the fan housing," [... ]The control module for the fans gets power all the time, the transistor shuts it off. If the transistor goes bad, then power flows all the time, as it's not supplied with switched power, rather it gets constant power."
Which appears to require removing the blower - given that the air seems to favour the right side, I assume the right blower is the culprit. And in my car, that's the driver's side. Warrjon notes that "Darlinton has failed short circuit which will turn the blower on all the time even with the ignition off. If it is the Darlinton you can substitute a MJ11016 available from RS Components."
The part appears to be readily available, even in Japan.
However, the fun appears to be in getting the blower in and out from the driver's side. I've worked under there before, and it's a very awkward position. Even in a car without airbags, either driver or passenger, it could be rather unpleasant.

That is, of course, assuming this is the issue. Hence this post. My assumption, based on JagBoi's post, is that the control module is getting power all the time now that the Darlington transistor has failed.
Any thoughts, suggestions, advice, and so on would be most gratefully received. Especially about whether these things just fail, or is there a cause that needs to be dealt with first.

Many thanks in advance....

 

Removing the fan is fun and games, SDSD. You have to remove the shinlevel trim, unscrew any electrical brackets inthe way, then head in the footwell, looking up with a torch, you will see two nuts going into vertical brackets, one each side of the fan. These have to be undone, then, jamming the lower fan flap OPEN witha piece of wood, PULL HARD on the entire fan motor casing, maybe levering it side to side and front to back a bit, eventually it will come out. The seam on the top vent to the bodywork "gludes" it in place after the years have gone by.

The flap at the bottom must be held open as the top flap cannot get through ther bodywork hole unless it is. Pic attached showing one of the brackets that hold the fan assembly the bottom nut of which must be undone. You CAN get the fan out with the steering column still there, but it is not exactly easy! Then there is re-attaching the silicone ducting afterwards...

LHS of the two vertical fan brackets ringed in blue.

 

Thanks very much, Greg. From what I've read, including your helpful post, it's a fundamentally straightforward but fiddly and time-consuming job. I'll try to find time to tackle it myself, however, as I can imagine labour costs would add up.

Feeling a little rattled here, if you check the news..... (But everyone is safe.)

 

Based on my experience, I'm assuming that transistor has failed. It gets power all the time and supplies a ground when needed. If that fails, it grounds all the time and the blower runs continuously.

Yes, removing the blower housing isn't the most convenient, but it's not too bad. There are 4 bolts ( I think) that hold it. Might only be 3. You'll need a long extension ( about a foot long) to get to the top ones. The bolts are either 7/16" or 1/2", sorry I can't remember the specific size. Once it's unbolted, you'll need to manipulate the recirculation flap to get the whole housing out of the car, as the flap goes into a cavity in the cowl. I can't remember if the flap has to be closed or open to allow it to come out, but I did recall having to move it from the rest position. On the drivers side I'm pretty sure the instrument cluster needs to come out, but that gives better access. It's just a few screws and unplug the harness, that's easy.

I wouldn't class this job as difficult but it is awkward space to work in and that makes it unpleasant.

 

SDSD,

Glad to hear you're safe.

I've been putting off the Darlington replacement for some years, but I do need to do it (RH fan runs on 2nd speed even if control set to 1). So I'm looking forward to seeing pics of your progress.

Good luck

Paul

 

This post on another site might help. Even includes completely replacing the circuit board if necessary.
https://www.jag-lovers.org/xj-s/book/acblower.htm

 

I have worked under there before, and found it a highly unpleasant position. I am neither short nor all that slim, but I'll see what I can manage. First thing is to order the transistor. I can find the MJ11016 online easily enough. If I read the link jal1234 posted, it seems that the transistor needs to be soldered on. So the next thing I need to do is find the soldering iron I bought a few years back and promptly mislaid....
Thanks for all your help and wisdom, everyone.

 

I think the original transistors are rated for 20A, you can get heavier ones that are 30 or 50A. Those work equally well if you can't find the original spec.

 

I've ordered a pair of the 30A MJ11016, figuring that if one transistor has gone, the other is probably soon to follow. When they get here, I'll see how agile I feel....

 

Very minor update:
My parts having finally arrived, I pulled the 20A fuse for the left-hand fan from the passenger side (left) fuse box, and that cut the blower. The other blower still works when the unit is turned on, giving heat (not so much cold, though hard to test in midwinter), and the whole unit turns off when switched off. Heat comes from all vents where it should save the left-hand (passenger) vent. It didn't come from there with the fuse in, either, so I think the ducting may have come loose.
Anyway, that means my initial diagnosis was wrong, and it's the left-hand blower that's the problem. Being the passenger one, with a non-airbag car, that should be a LOT easier to access ... I hope.

 

Yes, the passenger side is much easier to access. You got lucky!