Locate the negative terminal by following the black ground cable, or looking for the negative symbol (-) or the letters NEG. Tuck the cable along the side of the battery to ensure it can’t accidentally come into contact with the negative terminal.
Loosen the two bolts going through the slot on the alternator bracket, but do not remove them. Make sure the bolts are loose enough to allow the alternator to slide within the bracket.
Place enough force on the pry bar to pull the drive belt until it is tight over the alternator pulley. Choose the area of the engine you pry against carefully to ensure you do not crush any coolant lines or electrical connections.
Make sure the bolts are tight before releasing the pry bar; otherwise the tension of the belt will pull the alternator back to its previous position. This step may be easier if you enlist a friend to help you.
You can also purchase belt tension testers at many auto parts stores that will tell you whether or not the belt is tight enough. If the belt is not tight enough, loosen the alternator bolts and try again.
Make sure the ground cable is attached securely to the negative terminal as it will cause the vehicle to die if it comes loose.
Check the service manual for your vehicle to determine which way you can reduce the tension on your drive belt. If your belt has been damage or is showing signs of excessive wear, it should be replaced instead of simply tightened.
The drive belt likely snakes through a number of pulleys in order to power multiple accessories within your car. You may also be able to find a diagram of the drive belt’s route on the auto maker’s website.
The wrong belt could fail to power the vehicle’s accessories or even cause internal damage to the engine. If you feel you have purchased the wrong belt, return it to the auto parts store and get the proper belt before moving forward.
Check the belt against the diagram or picture again once you’ve finished running it to ensure it looks right. You will need to maintain pressure on the tensioner pulley while getting the belt over it, so this step may be easier with a friend to help.
Use a ruler to check to make sure the belt is under the proper amount of tension. Place the ruler along the belt and try to pull the middle of it away from the ruler. If it moves more than a half inch, it’s not tight enough.
This may not be particularly difficult if your tensioner has broken. You may also consider replacing the drive belt while doing this, as it will have to come off anyway.
Take note of how the belt is run through all of the pulleys if your vehicle and owner’s manual does not have a diagram to follow. If you do not have a diagram, try taking a picture of the belt with your phone to use as a guide.
The locking pin provides the tensioner with leverage to exert force onto the belt. You will need to re-use the bolt you remove from the old tensioner when installing the new one.
Make sure to make it tight, as there will be a good amount of force on the tensioner when the vehicle is running. The tensioner will likely not seat properly without the pin inserted in the right place, so if you are having trouble getting it in, check to ensure the pin is sliding into the hole in the block or bracket.
Test the tension of the belt by placing a ruler alongside it and pulling the belt away from it. If the belt will come further than a half inch away from the ruler, it is still not tight enough.
You can purchase belt tensioner tools that will measure the tension of the drive belt and let you know if it is too loose at most auto parts stores. If the belt seems loose, it likely requires tightening or replacing.
Dimming interior lights and issues with your electrical gauge can both also mean an issue with your alternator. If the lights get brighter when you accelerate, the problem may be the alternator rather than the belt.
Engine heat issues may also be caused by bad coolant, a leak in your coolant system, or a faulty water pump. Be careful driving a vehicle with coolant issues, as overheating an engine can cause significant internal damage.
The black lead from the voltmeter connects to the negative terminal on the battery. You can find the negative terminal by looking for the letters “NEG” or the negative symbol that looks like (-). The red lead from the voltmeter connects to the positive terminal, which can be identified by the letters “POS” or the positive symbol that looks like (+).
Even under optimal conditions, drive belts will eventually wear out and begin to stretch. Look for any indications that something has been rubbing on the drive belt and make sure to address it before installing a new one.
If you can see the tensioner pulley with the motor running, start it and watch for any movement in the pulley. The tensioner pulley should not move under the pressure of the belt when in motion.
