Drivers side blower stuck on.

[dpover532]

I noticed that the blower on the drivers side of my 1991 XJS has stuck on. Even turning off the car and the fan stayed on. My mechanic removed the fuse so now I need to find the issue. Has anyone had this happen to them? or does anyone have any suggestions?
My car is currently totally stripped down at a paint shop having a complete respray. First job when the paint is baked is fix the AC.

[almcl]

I think you have the Delanaire Mk III system and this sounds like another failure mode of the little electronic board that is mounted in the fan motor's outlet duct. There is also a relay that could potentially be stuck on, if the motor is stuck in 'high speed' mode.

I can't find a description here, so this is a link to another site with a system description: http://www.jag-lovers.org/xj-s/book/acblower.htm

[dpover532]

Thank you for your suggestion. I will read up on that.

[PaulGover]

I think you have the Delanaire Mk III system and this sounds like another failure mode of the little electronic board that is mounted in the fan motor's outlet duct. ...

The component on there is a large power transistor. The one originally fitted is no longer available, but there are many superseding equivalents with the same physical arrangement and higher current and voltage ratings. The last time I looked, an appropriate fitment as an MJ11016, available from CPC for under £10. Take care to retain the insulating washers and plastic sheet under it, though I think you can get an appropriate mounting kit from the same source if your drop them.

[ng4xjs]

Mine is stuck off guess it's the Darlington transistor but so annoying. Doesn't work on any setting (and not the fuse).

[PaulGover]

Mine is stuck off guess it's the Darlington transistor but so annoying. Doesn't work on any setting (and not the fuse).

Ah, that won't be that transistor, or at least, not by itself. Max speed uses a relay which shorts the transistor out of the circuit (you don't want to run about 30A through the transistor to run the fan at full blast, and anyway the transistor slightly reduces the voltage to the fan).

You probably need to get a voltmeter to the various connections in the circuit until you find the break. AFAIR, not that much fun, you have to take various covers off and lie in unnatural poses with a lamp strapped to your forehead! Be careful not to short things out; there are sensitive electronic components waiting to fry.