Automobile Bulb Testing
Testing the wiring in your automobile can be a difficult task if you don’t know what to look for. Repairing it can also be hard, depending on where the fault is. I have created a few diagrams, here. These are based on a basic series circuit. A lot of people come across dim bulbs on their car, so I showed a few ways to test the circuit. If the bulb is dim, test the load or power drop across the bulb as shown here. You should have battery voltage. The best way to test what battery voltage is to check the battery at the posts. A good test will show 12v; check your automobilemanufactures recommend voltage for your battery. If it goes below a certain voltage it might not be able to recover when being charged. If you get anything lower than 12v; then there could be a problem. Next you would need to check the power at the bulb has seen here. If you have anything other than 12v; again some more diagnostics will be need on your part. The best way I found to test a circuit is to break it down. This will require some access to wiring harnesses and fuse boxes. Start with the easy points, the fuse, the ground, the bulb. Never assume all those are good. Some cases a visual look at this may miss the problem. If you check a fuse and it looks ok, but still you have no power. Use your meter to check the fuse while it is in the fuse box location. If you find 12v on one side and 0v on the other then the fuse is bad. When checking a ground point you will need to find the stud and wire of that circuit. These can sometimes be found in your wiring diagram. They are usually black wires, with eye sockets on the end. They can be fitted with a nut or bolt. Make sure the nut or bolt is tight and there is no rust on the location. Any resistance can cause a problem in your automobile circuit. You need a clean ground to complete the circuit. Checking the bulb socket can always be a good point for loss of power. Tangs inside the socket can become loose or bend causing the bulb not to work or be dim. Make sure the bulb is good by check the filament inside of it. Look very close at it, sometimes it make look good, but one point make not be contacting. Try the bulb in a different socket; if it works then you know you have a circuit problem that needs repairing. Remember to take your time when testing your automobile wiring. If you’re not sure what to check always refer to a wiring diagram. Once you have found the fault, all you will need to do is repair it. If you really fell uncertain, take it to a repair shop. You will fell better when you can fix it. Written by U-Can-Auto-Repair

Paul Valdez