A/C Belt Diagnosis

Today's automotive belts are made of neoprene or EPDM. These belts squeal if there’s not enough tension or if the belt is worn and stretched. Today's EPDM belts last much longer, because the material used in them has more elasticity. This additional elasticity makes them much less vulnerable to cracking. It’s best to use a belt wear gauge when considering the replacement of a belt.

A/C Belt Squeal and Belt Gauge

A good belt rides a little above the pulley to allow dirt and debris a pathway out of the belt system. As the Neoprene or EPDM belt wears, the gap between the pulley and the ribbed belt begins to decrease. It rides deeper into the grooves of the pulleys and prevents dirt and debris from leaving the belt system. This is known as hydroplaning. It may not be noticed, because of the belt’s ability to resist cracking, it may appear to be fine.

EPDM belts are designed to resist noise and cracking. This is why a belt wear gauge is best for diagnosing many automotive belts. A loss of 5% of the belt’s material will result in a loss of belt performance. A belt wear gauge measures the depth of the belt. On a new EPDM serpentine belt, the gauge would raise above the ribs. If the belt is worn, the gauge will sink into the belt, indicating the need for replacement.