So after a year I've finally gotten around to troubleshooting why my fresh air blower fan doesn't work. Some deoxit and scraping away crud with a long screwdriver got the low and mid settings on the fan to work. It seems though that the little borders that create a detent in the slider movement between settings is preventing the contact arm from reaching the third setting. It's like the contact arm isn't long enough to make it over the last detent border. Anyone know if there's anything that can be done? Any adjustments?

You can (hopefully!) see how much bigger the last detent is in the pic. Not an easy shot to get through the ashtray hole!!!

The last "detent" is deeper because at one point that connection got too hot and melted the plastic causing it to sink. I've seen it happen a few times. You can try removing some of the excess plastic and bending the arm some to make full contact. Also clean those connections real well so it doesn't happen again.

Resistance has built up enough heat to melt the plastic behind the contact. Bending the contacts doesn't help much.
I have the same problem, still looking for solutions.
Mike

Holy crap, that's a little scary! Another maintenance to-do item, I guess. Is the only other way to access it, other than through the ashtray, by removing the dash top? If so, I'll just be living without a Hi setting for the foreseeable future.

Also, my fan is pretty rattle-y. Anything to be concerned about? I just replaced the fresh air box seal, and don't really have any desire to remove the air box ever again!

It happens because the fan motor is old and dirt interferes with its movement. As a result, it draws more current and melts that contact.
Clean the motor and re-grease it. Maybe you need to re-bush or just replace it.
Clean that contact, remove any melted plastic that can interfere with the moving arm.
You may want to remove that speed at all. You can shift the wires and get rid of the lowest speed that doesn't do much anyway. Then just add a stopper so you don't go over the middle contact (or remember that the fan lever will not work all the way to the right)

It's not just the contacts there. It's the whole circuit through the resistors in the fan housing. If there's too much resistance, something is going to give. I managed to get my mid and high speed settings working, but the low-speed resulted in smoke. I have since disabled that setting.

Been there done that.

From under the dash, you will see a nut holding it to the chassis. Undo that nut and it will slide out of the dash, though at this point the cables will be a problem. Might be able to tilt it enough to get your hand in there well enough to clean.

Like Doug said, the plastic melted and pushed the contact in deeper. Cut/sand the bubbles, I used a sanding disc on a Dremel, and pull/bend the contact back to level.
A lot easier to just swap wires.

On closer inspection I can see now that those "detents" are actually melted plastic and not supposed to be there. Yikes!
I was able to clean the contacts by reaching under the dash and up behind the controller with a q tip in one hand, and spraying contact cleaner from the front through the ashtray opening. A bit of the old reach around!
Went ahead and went through the entire car cleaning every contact I could find while I was at it.
I'm about a week away from permanent top off weather until fall, so not a huge issue that it's all working. I'll prob just leave it as is for now. The medium speed isn't bad if I need it, and I really don't feel like taking the air box off again to clean the fan. I spent almost 2 hours in the front trunk today getting the new seal in. I've got muscles in my arms and back that I didn't know I had that are sore from trying to push and hold the air box into place while getting the mounting screws in. In addition to a raging headache from gas fumes from being right above the gas tank.

If you still had the Scotty Orange teener you could have just poked your fist thru the nearest rust spot to access.

Haha! I know right!
The fresh air blower didn't work on that car either. But the holes in the back of the front wheel wells and in the front of the floor pan provided plenty of fresh air straight to your feet anyway!