either too tight or to loose, need about 8mm of give between alternator and drive pulley
Belt slipping? Bad bearing in belt driven accessory?
There is no fan belt on a Mazda Miata.
There is no fan belt on a Miata, it is cooled by electric fans.
Change the belt
Change the belt
Look to the alt. belt. It may squeal under load.
The belt will not generally squeal, but the water pump often makes a "Scrapy-scrapy-scrapy" sound.
Very often it is not the alternator, but the belt that squeals. This can be checked by rubbing a little soap on the belt, if the squeal goes away, you know it's the belt. The belt may squeal for a number of reasons: the belt is new, the belt is old, the belt tension is too tight or loose, the belt is cold (the squeal goes away on it's own when it warms up). Some belts just squeal for no discernable reason, but there are 'belt dressing' sprays available for sale that sometimes help. Always check the belt before spending a bunch of money on a new alternator that may not be needed.
A loose belt. Most likely the alternator belt, if it doesn't squeal when you make a sharp turn.
The squeal is often caused by the power steering belt slipping. Check the serpentine belt to see if it needs replacement.
The 1.8 litre four cylinder engine in a 1995 Mazda Miata has a timing BELT
Timing Belt