When I turn on the air conditioning on any of the settings it roars on at full speed and cannot be reduced by the speed regulation switch. The switch works at all speeds with heat and regular air,
any ideas ?
Mik

Do you have a 760 with the Automatic AC system? I don't know anything about them but I believe they have a control board which adjusts blower speed to keep car at a preset temperature. If so, then this board could be bad.
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744 & 745 16v 4+OD, 245 SE auto, 242Ti 4+OD, 245DL auto parts car

This is a problem that I've seen come up in lots of posts while trying to solve my own problem. I wish this was my problem because I am told the solution is fairly simple: the controller on the dash feeds into a small black box which contains a couple of relays and a couple of transistors. This is mounted on the top of the airbox the blower fan sits in, behind the glovebox. It looks like the bottom 1/2" of a black pyramid and has 2 plugs leading in/out of it.

Its role is outlined on the diagram(s) you can find here:
home.eol.ca/~clubshub

As I have been told one of the indicators that this system has failed is exactly the problem you're having. You may still want to take it to a garage because the part is difficult to extract, harder to replace, but if you tell them where you think the problem lies they won't waste time (ie. your money) doing lots of unnecessary diagnostics.

Good luck!
blurp
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1983 240 Turbo

By the sounds of things, it sounds like the regulator coils have shorted out
so the amount of resistance is low meaning the fan will run "Flat Chat"
when switched on at any position.

This problem can be caused by something coming through the fresh air vent
near the bonnet and coming down the intake tube to the heater unit and then
getting blown through to the airvents and possibly getting lodged on that
along the way causing it to bend the coils over causing it to short out.

Good luck mate!

That sounds pretty likely. Or something like that: when I first got the car I could hear the fan but nothing was coming out of the vents. After an exhaustive process it was determined that the evaporator was completely stuck shut, quite possibly coated by some sort of stopleak product leaking out of a small hole under pressure and coating the fins with sticky goo, eventually clogging with dust and dirt. At that time I removed (and stomped angrily on) the evaporator but the resistors, which believe protrude into the air path near there may either have been damaged slightly in that process or themselves coated with the aforementioned sticky goo. After a time they might just give out.

I'm hoping this is it because this break is making me loopy and my wife really hates riding around with the glovebox out!

I will pull the part today and, if warranted, stomp on it!

Best regards,
Blurp
ps. You think this is the OP's problem too? I hate to hijack a thread.
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1983 240 Turbo