Solenoid Problems -- Diagnosing Car Electrical Problems Properly

Solenoid problems are a very often hidden problem that can cause quite a bit of electrical problems.  Most people have never heard of a solenoid, and when their vehicles start having electrical problems they automatically assume that the battery or the starter is dead.  Very possibly, the solenoid could have gone bad.  A solenoid is generally just a coil of wire that's wrapped around a hollow non-magnetic core. The solenoid receives an electric current from both the ignition switch as well as the battery.  The small electric current from the ignition switch forces the solenoid to clamp together a pair of heavy contacts.  This allows the large electric current from the battery to flow to the starter and turn over the engine. Generally, when a solenoid gets broken, the two metal clamps won't operate anymore to complete the circuit, making it impossible for power to flow from the battery. 

If your car won't start and you've changed your battery or jumped it, and if there's no sound at all out of the starter when you turn the key, then it's a good bet that your solenoid is bad.  Depending on the solenoid, you may or may not be able to test it.  The solenoid's job is simple, it connects the circuit between the battery and the starter.  So when a solenoid is broken, it no longer is able to connect the battery to the starter.  So testing a solenoid is just a matter of bridging the connection and allowing power to flow from the battery to the starter.  If you have a metal tool with a rubber handle, you can touch both of the posts with the metal, thus bridging the connection and allowing power to flow.  Just be sure not to shock yourself.  This will not work in every case however, because solenoids are different and not all of them have easily accessed ports like this.

We once had a riding lawnmower with a bad solenoid and would keep a long screwdriver in the glove box to use every time we needed to start it.  We would reach in and touch the screwdriver to both the ports on the solenoid, and without fail, the lawnmower would start right up every time.  We eventually changed out the solenoid, but since the solenoid is a very simple part that only functions to bridge the connection between the battery and the starter, we figured it wasn't that big of a deal.  In fact, having an easily accessible faulty solenoid is actually quite a good anti theft system.

The solenoid can break through a variety of factors.  One factor is just normal wear and tear which causes all automotive components to eventually wear out.  Another factor that can cause a solenoid to go bad is poor technique in jump starting a car.  If you have jump started your car recently or helped a friend jump start theirs, then it's possible that you've accidentally knocked out your solenoid.  If when the jumper cables are hooked up to your battery posts, you accidentally touch the copper of the other two jumper cables together, it'll send a spike of power through your system that can knock out your solenoid.  This generally happens to the car that's doing the jump starting and not the one with the dead battery.  Generally poor jump starting technique happens when a person hooks up the cables to the powered battery first, and then while walking over to hook up the dead car, the heads of the other two cables touch, thus sending a surge through the system which either knocks out the solenoid, or else weakens it so that it becomes faulty and fails at a later date.  So don't ever touch the heads of the jumper cables together.

If you've gotten a faulty solenoid and you want to replace it, it should be a fairly simple process, depending on whether or not it's buried under other components.  If your electrical system is constantly acting up and you've already replaced the battery and don't know what to do, it might be a good idea to slowly start replacing the rest of the starter system.  The solenoid is a good place to start because it's a small part with little installation.  If you go into your local auto parts store and find the solenoid you need for your car, they should be able to give you further instructions on how to install that particular solenoid into your vehicle.  Just make sure you disconnect your battery first so that you don't accidentally shock yourself.