My guess is that it is the tensioner assembly. If you are getting a chirping noise especially when its damp it is the sepentine belt slipping due to lack of constant tension. The tensioners are notorious for failure.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T