Hi when I bought my car I had the screaming fan motor issues that most seem to have from time to time, so I did what most of us do checking the gully, removing the pollen filter drop of WD40 on the top motor bearing etc. this did not seem to have any effect on mine.
One cold and rainy night just before xmas with all the family on board it decided to stop altogether, having the effect of completely misting up the windows in a very short space of time, previous to this it had been slowing on what ever speed when ever I went over a speed bump pothole or what ever.
Now I was going to have to look into it! upon removing the glove box I found that the fan unit was not properly secured so it was obviously a problem before.
When I removed the fan unit, I also removed the fan motor from the plastic casing, having done so I could now see that the bottom bearing of the motor had been getting wet and is badly worn. Lubing the top bearing with oil cause,s carbon dust from the brushes to stick to the commutator and the brush holders causing the brushes to stick and arc on the commutator causing complete failure. I cleaned all with brake cleaner spun the armuture and cleaned the commutator with fine grade wet and dry, replaced the brushes with some I found in an old drill, Having cut them to size, the resistor pack had been repaired with tape and a paper clip, I replaced the tape and paper clip with low melting point solder. Packed the bottom bearing with HMP grease,put it all back together.
Working OK for now but the bottom bearing will no doubt cause problems again.