Ok..I have a 85 300SD and Love it. Drives awesome, lots of power to get me anywhere fast, I even got a letter from the state of Texas that someone complained about the smoke...can you believe it? Anyway the one problem that is the fuse for the A/C fan...the 25amp fuse blows, sometimes it blows the same day I put it in, sometimes it will last a week. I read on here about either some kit to upgrade it to a 30 amp or changing out the brushes on the motor. My question is this....which is better? If the fuse kit is best, where can I get the kit? if changing the brushes is best how do I go about that..like how do I get to the fan, where do I get the brushes? I also have a problem with the defrost blowing all the time..I get some air from the center vents but it seems more air is blowing out of the defrost...I tried looking back in posts but since the disk crashed it doesn't go back to far.
Thanks

Anyone got some advice on this?
I replaced the fuse again last night for my ride in this morning...it didn't blow but then again I had it on the eco switch for some warm air. I did start to notice a slight burning smell so I turned it off..the smell got worse for a couple of sec's then went away so I didn't dart off the freeway and bail out. And as I look out my window I can see her just sitting there not erupting into flames, so I atleast have a way home. I think I am leaning more toward the fan brush replacement. Is there still a thread out there that deals with this. I need to know where the fan motor is, how to get to it. I remember parts of a thread on replacing the brushes and think I can figure it out from there.
How do I get the outside temp to go from C to F? or am I stuck with C?

Start digging under the dash below the glove box. You'll find the fan motor.
Not too hard to get to.
It may just need cleaning, oiling.

tap the bugger with a brass hammer. possibly the brushes need a little 'jolt'.

tonight when i get home I will take a look and see what needs to be done..maybe replace it with a hairdryer... you never know.

I pulled the fan and gave it a good cleaning using some contact cleaner and compressed air. Re-installed it and craked up the eng. I turned the a/c on and WOW...the air flow was more then I could have dreamed, and the low and auto works now too. I ran it for about an hour and a half sitting still with a 9 year old behind the wheel gooseing it every now and then to make some black smoke...she thinks it is cool. And the fuse never blew. I let it sit because that is the conditions it would blow before in traffic. Thanks for the help.

Search for ACC vacuum problems, there's many posts covering this. When ACC vacuum pods get no vacuum on a 126, air blowing out of defrost vents is what you get. Been there.