in hot summer, the fan & heat related problems are very Common. so don't worry much.
Well, i will never suggest to put fan in the direct mode in any case. 90% mechanics suggest to do so, but this is wrong. Experts like Xulfiqar bhai have repeatedly mentioned in his posts.
Have you tried to replace the whole fan ?
if it works, then have it replaced. Its not very expensive.
Seems that fan motor has got weaker. so instead of replacing motor, its better to replace the whole fan (including motor). You can purchase it as new or in 2nd hand as well (if the condition is good).