LINK 9C6026 - Caterpillar

Inspection
Belt tension should be checked initially between the first 20 to 40 hours of engine operation.After the initial check, the belt tension should be checked at Every PM Level 1 or Three Months.To maximize the engine performance, inspect the belts for wear and for cracking. Replace belts that are worn or damaged.For applications that require multiple drive belts, replace the belts in matched sets. Replacing only one belt of a matched set will cause the new belt to carry more load because the older belt is stretched. The additional load on the new belt could cause the new belt to break.If the belts are too loose, vibration causes unnecessary wear on the belts and pulleys. Loose belts may slip enough to cause overheating.If the belts are too tight, unnecessary stresses are placed on the pulley bearings and on the belts. This may shorten the service life of the components.Remove the belt guard. Inspect the condition and adjustment of the alternator belts and accessory drive belts (if equipped).To check the belt tension, apply 110 N (25 lb ft) of force midway between the pulleys. A correctly adjusted belt will deflect 9 mm (0.35 inch) to 15 mm (0.59 inch).If the belt does not require replacement or adjustment, install the belt guard. If the belt requires adjustment or replacement, perform the following procedure to adjust the belt tension.
If the engine is equipped with a refrigerant compressor (air conditioner), the belt for the fan drive, the alternator, and the accessories will have an automatic belt tensioner.
If the engine is not equipped with a refrigerant compressor, the alternator is used to adjust the belt tension.Adjustment
Alternator Belt
Illustration 1 g00485289
Typical alternator mounting
(1) Adjusting nuts
(2) Mounting bolts
Slightly loosen mounting bolt (2) and adjusting nut (1).
Move the pulley in order to adjust the belt tension.
Tighten adjusting nuts (1) and mounting bolts (2). Refer to the Specifications, SENR3130 in order to locate the proper torques.
Install the belt guard. If new belts are installed, check the belt tension again after 30 minutes of engine operation at the rated rpm.