Replacing an AC Belt on an Altima

I recently had the pleasure of helping my brother replace the air conditioning belt on his 1999 Nissan Altima. Most vehicles sold today either have one serpentine belt that weaves its way around all the pulleys, or two separate belts. In the case of the Altima, the main belt drives the power steering, alternator, and water pump. A secondary belt drives the air conditioning compressor.

As a side note, reading the belt diagram or following the route of the belt is an easy way to identify these automotive components.

This diagram is general representation of a two belt system. The red line represents the main belt and the blue line represents the secondary belt.

Luckily for us, the AC belt was the outer-most belt. This meant we did not have to take the main belt off in order to change the secondary belt.

Whenever changing a belt, you will always have to relieve the belt tension. Some systems use a spring loaded automatically adjusting self tensioner that must be rotated to relieve the tension. On the Altima, the belt tension is manually adjusted by a bolt. The belt tensioner pulley is attached to a pin that can slide up or down in a bracket. Here are the steps taken to replace the belt:

1. Remove the bolt and washer from the belt tensioner pulley (blue arrow)
2. Remove the adjusting bolt (red arrow)
3. Note how the pulley, pin, bracket, and adjusting bolt go together. Remove the pulley and inspect it. Lubricate or replace if needed.
4. Remove the old belt while taking note of how it is routed.
5. Reinstall the the pulley assembly but do not tighten the bolts yet. The pulley should freely slide up and down in the bracket.
6. Install the new belt. Move the pulley to its highest point in order to get the belt on. It may still be a tight fit.
7. Make sure the belt is properly seated in each of the pulleys - the crankcase (engine), AC compressor, and tensioner.
8. Tighten the pulley bolt (blue arrow), then tighten the adjusting bolt to 26 ft. lbs.
9. Check to make sure the belt is on tightly enough. To check, measure the amount the belt will deflect when you press against it at a point half way between two pulleys. The amount of deflection should be about 1/4" If it deflects more than that, tighten the adjusting bolt. If it does not deflect, then it is too tight and you need to loosen the adjusting bolt.

It is also a good idea to clean the the pulleys when you have the belt off. You should also check each pulley to make sure it spins freely (with the exception of the crankcase pulley). If any of the pulleys grind or resist spinning, try cleaning them or replacing them.