Rev the car tapos silipin mo kung sabay ikot ng dalawang belt mo. Usually kasi 2 rings ang crankshaft pulley, yung inner (larger ring) nagiikot ng belt ng power steering, waterpump (critical engine stuff) tapos yung outer (smaller) ring nagpopower sa alternator at aircon.

When you rev it abruptly, you'll see na di iikot yung belt ng isa, usually yung outer ang di iikot.

Kapapalit ko lang din ng akin a few months ago.