Mazda Repair: 2002 protege alternator/belt, rule of thumb, deflection

Question
I read on this forum that maybe one or two people have had a similar problem that my protege is having.  It's a 2002 protege and it's making a very loud horrible squeeling noise every time i start it and/or drive it. This happened in the past when the alternator belt just broke on it's own and the mechanic replaced it - within a couple days it was making that noise again and the mechanic told me that they put the wrong size or kind of belt on the car. Well, it has been at least a year after they replaced the belt for the 2nd time and the car is making that squeeling noise again. My husband replaced the alternator belt just recently because it was making the squeeling noise out of the blue but now the squeeling sound is even worse. He went out and put WD40 on it but that didn't seem to have any affect. Should we replace the alternator or try adjusting the belt again?

Answer
first replace the belt using wd40 can cause it to weaken and crack. and adjust it. most of the time a belt squeels cause it's been over tightened. belt deflection is important as a rule of thumb 7-11 inches between pulley centers deflection should be about 1/4 inch 12-16inches apart about 1/2inch. if you find that it still squeels use belt dressing NOT WD30