Basic Auto Mechanics – Week 2

Week 2 of the basic auto mechanics class at East Brunswick Vocational School was all about the electrical system.  It was a very high level review of the most basic aspects of the electrical system.  It covered the battery and the connections to the starter as well as some basic troubleshooting of no start issues.  We also covered how to use certain tools in the troubleshooting of simple electrical issues.  We went over fuses and circuit breakers and we were shown how a basic circuit worked in a car.  The class is divided into two sections, there is a short classroom section where we can take notes and the teacher goes over a couple of things and then there is a shop section where we experiment with the devices that were discussed in the classroom.

The first order of business in the class was the battery.  We were told that there was no difference between a lifetime battery and a 60-month battery and that we should save our money and buy the 60 month one.  The way to prove this he said was to weigh the batteries.  They probably weigh the same which indicates that they are identical and that there is no extra capacity in the lifetime battery.  The companies are probably just hoping that you either sell the car or forget that the warranty was purchased.

We learned that in a sealed lead acid battery, that there are actually 6 2 volt batteries inside that are connected in series to produce the 12 volt battery that is required by your cars electrical system.  You could also connect 2 12 Volt batteries in series to produce a 24 Volt charge.  If you are looking to gain capacity in your system you could connect 2 12 Volt batteries in parallel and that would make the charge last twice as long.  You could do this for as many batteries that you could and get differing results in either voltage or capacity depending on how you hooked them up.

In a series connection, you connect the positive terminal of one battery to the negative terminal of another and you loop the last connection back to the first battery.  This connection gets you more voltage, so that 2 12 Volt batteries would get you a 24 Volt connection.  In a parallel connection, you connect the positive connection of one battery to the positive connection of another.  You do the same with the negative connections.  This gets you more capacity but does not increase the voltage, if you hooked two identical batteries together that were just like this, the batteries would last twice as long.

We went over how to safely jump start a car.  With all the electronics in the new cars, it is possible to send a surge through the system when jump starting a dead battery which could short out some of the complicated devices that are connected to the electrical system.  The best way to jump start a car is to hook up the terminals, positive on the good battery first, then the negative on the good battery, followed by the positive on the dead battery, and finally the negative on the dead battery.  You should see a very small spark at the terminal when you connect it and that is normal since you are completing the circuit.  If there is a large spark there is something wrong.  (For safety, if there is a smell of rotten eggs under the hood, you should not attempt to jump start the vehicle.  The battery is damaged and is at risk of exploding.  If the battery is bowed and the sides are not straight, the battery is also damaged and should not be jumped.)  Now that you have the terminals hooked up properly, you should let the battery charge for 20-30 minutes.  After that amount of time has passed, you should disconnect the jumper cables and attempt to start the car with the dead battery.  The surge occurs when you leave the jumper cables connected and start the dead car.  The alternator on the good car senses the drop in voltage on the system and ups the amperage in an attempt to compensate for it.  This sends a large surge through the system which can damage electrical components in the car.  This is why we disconnect the jumper cables before attempting to start it.

Troubleshooting no-start conditions were the next order of business.  The following is a list of steps to take to find out what the problem is and why it does not start.

  1. Try to start the car – see what happens, if it starts good, if not step 2.
  2. Turn on the lights and try again.
    1. If the lights dim when turning over, the battery is the most likely culprit
    2. If the lights go out, the battery is dead.
    3. If lights stay bright, there might be a dirty connection. In this case, clean the connections and try again.  When this is the problem, there should be heat at the terminals and the cable may feel hot to the touch.
    4. If the lights stay bright and you hear a click, the problem is with the starter.

That is a simple list of troubleshooting steps to troubleshoot a no starting issue with a vehicle.  This does not take into account any fuel system or ignition system components and is just a list of the problems that could be occurring with the charging system.  This was stated during the class but this is meant to troubleshoot a no-start condition up to the point where all the common issues are addressed and before you move into the other systems of the car.

At this point we moved into the shop and my notes kind of trailed off.  When we are in the shop it is a lot of hands on and actually doing what troubleshooting steps are necessary to get down to what the problem is.  I will attempt to summarize what we went over in the shop but it will not be as detailed as the notes above.

We went over how to use a voltage meter and we tested the voltage in a live battery on a bench.  We then went over the basic electrical tool of the test light.  We were shown how a simple test light can tell us whether or not a connection is good by just lighting up.  It tells us if there is voltage in the circuit that we are testing as well as if there is continuity.  We tested this with connections wired to a brake light on a bench and went over some switches and how they worked.  We tested the connection before the switch with the test light and after the switch to see that the continuity was broken.  With the switch closed, we were able to see that the continuity was restored and the light was on, as well as the test light.  We also briefly touched on the Ohm’s or continuity test function of a fluke meter.  I asked about the resistance numbers but all I got was that is measured the amount of resistance in the wire that you were testing.  This was a basic class, as well as a time limited class, and there was not a lot of detail in the Ohm explanation.

The last thing we did was disassemble a starter and reassemble it.  I learned that the wearable parts are pretty much the brushes that touch the metallic coils that spin on the shaft to get the starter to turn.  The metal on the shaft can be machined and cut so that you can reuse it, but the brushes must be replaced.  Other parts that should be replaced are the brass ends where the shaft rests when the starter is fully assembled.  The teacher stated he would replace those parts and put some grease in them to allow the shaft to spin freely.  We saw how the starter solenoid works with a spring that keeps the starter gear at rest until the key is turned and the magnet in the solenoid engages the clutch and pops the gear out of the starter to crank the engine.

We learned that the starter gear is on a drive helix so that when the starter is engaged it is able to slide into the flywheel without just slamming into it.  This helix actually turns the gear very slightly so that the gears of the starter slide gently into the gears on the flywheel.  We saw that the starter gear is actually a sprag gear that only spins under power one way.  After the engine is started, the gear will spin freely.  This keeps the starter gear from becoming damaged after the engine is started.

Overall, this class was pretty good.  I knew a lot of the material in it already but it was good to see the test light and fluke meter in action and have a quick overview of how to actually use them.  I have one in my garage but hardly use it because I really don’t know how and haven’t had a problem where I really needed it.  I also have never really used the test light I have because I did not realize how versatile it actually is.  I was also very interested in the rebuilding of the starter and getting it to work again after the rebuild.  It was not difficult to do but getting my hands dirty is always fun.  Next week we are on to the top end of the motor!




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