Have the mechanic explain and demonstrate the fault. Verify the timing marks and that the correct timing belt was installed. A timing-belt tensioner should be tested before reassembly; if it now tests bad, ask why it was not checked while removed and have the failed unit shown. A replacement tensioner is roughly $95. Treat incorrect timing after the job as likely installation error until proven otherwise. The A/C noise is a separate issue, and the A/C belt has no hydraulic tensioner.
The owner of a 2001 Honda Civic EX had the accessory and timing belts replaced after an A/C belt noise, although the timing belt had not failed. After about six hours, the mechanic said the timing could not be set correctly and blamed the hydraulic tensioner. The expert said a good mechanic should test the tensioner before installing the belt, and that incorrect timing more likely indicates installation error, such as misaligned marks or the wrong belt. The owner was advised to demand a clear explanation, proof of the tensioner test, and correction of the work. The A/C noise was identified as unrelated.
