If loud whistling noises from the engine compartment are detected when the air-conditioning system is turned on, this could be related to a defective belt tensioner bearing in the alternator. In this case, the old bearing (18 spokes) should be checked and optionally replaced by a modified bearing with 20 spokes (Fiat 46557129). After replacement, please check that the belt tensioner bearing and the compressor belts match. If their centering does not align, this must be optimized.
The centering can be optimized by removing the bearing and shimming with a maximum of two 0.5 mm washers (Fiat 13579771) on the compressor bracket.
Important safety note
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