You can buy these at nearly any auto supply store, and most hardware stores. You will also need an appropriate sized wrench with which to remove the battery terminals. Important: Always disconnect the negative (-) battery terminal first, and reconnect it last. This will help to keep from shorting the battery while connecting or disconnecting the terminals and possibly causing damage andor personal injury.
Seeking the Elusive Electrical Problem. Many times electrical problems are the most elusive, because they can occur intermittently. For example, the car engine may not work properly, but only after the engine warms up. Or the ignition works randomly. Perhaps the engine cuts out without notice while cruising down the highway. Then again, your car might have a faulty alternator or a defective wire.
These can often be difficult to bolts to remove. You may need to use a ratchet with a long extension to provide the necessary angle to access and turn the bolts. Pull the motor and harness out as one assembly. Once you have the assembly removed, you can separate the two pieces and replace the one that is malfunctioning. Re-install the motorregulator assembly. Once you have replaced the malfunctioning part, whether it was the motor or the regulator, it is time to slide the assembly back into the door's interior and bolt it back into it's original position.
If the battery terminals are clean and tight, then the next item to check is drive belt tension. If the belt which drives the alternator is too loose, then the alternator will not produce enough electrical current to keep up with demand. Many modern vehicles utilize a single belt which drives the alternator and other accessories. This system usually also has an automatic belt tensioner which always maintains correct tension and is not adjustable. If your vehicle uses a wide, multigrooved or so-called "Serpentine" belt to drive the alternator, then it likely also has an automatic tensioning device.