Testing a battery's performance and reserve (or amp-hour) capacity is not just a matter of seeing whether it will hold a charge (or checking the electric eye found on some batteries to see if it is green), so testing is best done by an auto technician at a repair shop. A professional can also determine if any problems you are having may be caused by something else, like your battery terminals or alternator. If a bad battery is the culprit, your mechanic will help you choose and install an appropriate replacement.
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.
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.
Sometimes, what people bother so much about turn out to be problems whose solutions are extremely obvious. This conversely means that checks for electrical problems in cars should start at the most obvious locations; the battery being a good example. Sometimes, a case of a car failing to 'start' or something of that sort could be simply as a result of an electrical contact breakdown at the battery. Here all that is required in the name of auto electrical repairs is something as simple as filing the terminals that connect the car to its battery.