Battery and Starting System Diagnosis and Repair

Since problems re;ated tp tje cranking system are common in vehicle malfunctions, what important simple tests need to be performed to solve the problem quickly and effectively?

1. A cranking system voltage drop test indentifies high resistance to the cranking circuit that can cause a slow or no start condition. 2. Every connection and conductor in the circuit, from the battery to the solenoid through the ground path is a potential problem area.

What reading indicates a full charge?

1. A reading of 1.265 indicates a full charge. 2. Alternately, an ammeter on the charger that slowly drops to zero or near zero indicates a fully charged battery.

How would you determine a battery state of charge using a hydrometer?

1. A specific gravity reading of 1.265 or higher at 80 degrees F (26.6 degrees C) indicates a fully charged battery. 2. A severely discharged battery will show a reading of around 1.120 or so. 3. A reading of 1,200 would indicate a battery that is 50% charged. 4. Temperature corrections must be made to the readings for batteries not within 10 degrees of 80 degrees F (or between 21.1 degrees C and 32.2 degrees C).

What should you do first when removing a battery and/or cables?

1. Always remove the negative cable first, and reconnect it last. 2. This will help to prevent arcing and a possible battery explosion should your wrench come into contact with ground when loosening the positive cable.

What are the procedures you should follow when jump starting a vehicle?

1. Always wear eye protection. 2. Then with both vehicle engines off, connect the positive terminals of both batteries with one cable. 3. Connect the ground booster cable to the negative battery of the booster vehicle and make the last connection to the negative battery terminal (s) of the dead vehicle. 4. This will prevent sparks in the area of the dead battery.

What is another way to check for high resistance?

1. Another way to check for high resistance is to crank the engine for several seconds and then feel along all the connection points and conductors for hear. 2. If any point is more tham just war,. there could be excessive voltage drop at the location. 3. Clean or replace as required.

How would you determime a rough estimate of battery state of charge?

1. By measuring its open circuit voltage. 2. With the battery under no load, measure voltage across the terminals. 3. A fully charged battery is 12.6 volts or more. 4. It the battery has been recently charged (whether inside or outside the vehicle), draw off the surface charge using this same method. 5. Allow the battery to sit for 15 minutes before testing, then test the open circuit voltage. Any reading less than 12.6 volts indicates that the battery should be charged.

How can the technician troubleshoot a cranking system inhibitor?

1.The technician can troubleshoot the system by checking the starter relay circuit. 2. The park/neutral switch is often located in the relay coil ground circuit. 3. If the starter relay coil lacks a ground, then find the park/neutral switch and inspect it slowly. 4. The switch is a very simple "open/closed' style switch that can be tested with an ohmmeter. A faulty switch should be replaced.

Some truck OEMs recommend capacitance testing of batteries, a number of different OEM instruments are available that will perform this test. How is this done?

1.The test instrument outputs a low potential AC signal and measures the return pulse. 2.The instrument outputs a low potential AC signal and measures the return pulse. 3. The instrument display is idiot-proof and usually reads in terms of OK or not OK. 4. The danger of using this method is that some good batteries could possibly be rejected as not OK.

What is the function of a cranking system inhibitor?

1.To prevent the truck from cranking under certain conditions. 2. Trucks with automatic transmissions use a switch on the transmission as an input device for this system. 3. Starter operation is prevented when the truck is in gear. 4. The starter will only function when the gear selector is in park or neutral.

Battery state of charge can also be determined by an open circuit voltage (OCV) test across the battery terminals. When the OCV has stabilized, what readings can be used?

12.6 volts or more -----------Fully charged 12.4 volts---------------------75% charged 12.2 volts---------------------50% charged 12.0 volts---------------------25% charged 11.7 volts or less--------------Fully discharged

What is sufficient when slow charging?

A 5 - 10 amp rate is usually sufficient, although a full charge may take overnight if the battery charge is low.

What do you do if a conventional battery is low on electrolyte level?

Add distilled water only. If a battery needs to have distilled water added on a regular basis, it would be wise to check the charging system for a potential problem.

How would you clean tapered battery posts and cables?

Are best cleaned witha type of scraper tool that actually peels away all the old corrosion down to bright shiny metal.

How can you monitor battery voltage during engine cranking?

Battery voltage during engine cranking can be monitored using a DMM. 2. Since all late model trucks have computers, it is crucial that cranking voltage be sufficient for all of them to work correctly. 3. Low cranking voltage will damage the starter due to increased amperage. 4. The battery voltage should not drop below approximately 10.5 volts while cranking.

What do you do after reinstalling battery cable ends?

Coat the terminals with grease or petroleum jelly, or use a spray marketed for this purpose, to resist corrosion. Protective pads that go under the tapered terminals serve the same function.

What should you do if the caps are removed during charging?

Cover the top of the battery with a moist rag. You can also monitor the specific gravity of the battery during charging to determine its of charge.

What does the life of a battery depend upon?

Depends in large part on the way it is secured in its mounts. 2. A battery with missing straps or mounts will bounce around and eventually damage the internal separator plates, which may cause an internal short. 3. Similarly, overtightened hold down straps may cause the case to crack.

What does the amount of time it takes to properly charge a battery depend upon?

Depends on its state of charge. The other factor to consider is whether to charge it at a fast or slow rate. In most cases, a slow charge rate allows for maximum batter life and performance.

How would you clean flat screw type posts?

Flat screw type posts are more difficult to clean; however, it is just as important that they be clean in order to transfer current with minimal voltage drop.

When should the ring gear be replaced?

If the teeth are worn or damaged.

What kind of area should batteries be charged?

In a well ventilated area. In addition, batteries should not be charge near heat sources or sources of ignition.

When should you inspect the battery box?

Inspect the battery box when the battery is removed. 2. Clean away any dirt, rust, and corrosion to help combat surface discharge when the battery is reinstalled.

What should you do to effectively troubleshoot the starting control circuit?

It is best to consult the wiring diagram. Properly understanding relays and voltage drop testing is essential for diagnosing starting circuit complaints.

What is wrong if a battery to not accept a charge from the start (zero amps)?

It is likely to be highly sulfated and should be disposed of according to Universal Waste guidelines.

What are magnetic switch (also know as MAG) assemblies?

Magnetic switch assemblies are typically four-post units with two large and two small terminals. However, some can also resemble large 5-pin mini-relays.

What does the LVD system Module monitor?

Monitors battery voltage and opens the circuit when the voltage falls below a preset limit. 2. The circuit remains open until battery voltage rises to a higher preset limit.

How would you test circuits to the solenoid?

Perform a voltage drop test across the two large posts on the solenoid while cranking the engine, just as for a battery cable or clamp.

What can result if a neutral safety switch and some bulkhead harness connections also part of the system?

Plenty of potential exists for trouble in the form of a no-start condition if everything is not in good working order.

Some starter manufacturers incorporate a built-in circuit breaker to do do what?

Protects the starter from thermal damage. This circuit typically resets when the starter temperature drops below a preset temperature.

What should you keep in mind when replacing a solenoid?

Quite often a pinion clearance adjustment needs to be made at the same time.

What does the starter control circuit include?

The starter control circuit includes those components between the key start switch and the magnetic switch (or starter solenoid itself, if there is no magnetic switch in the circuit).

What happens when some manufacturers do not use a separate magnetic switch between the key switch and the starter solenoid?

This makes the key switch circuit moderately high current.

Why are low voltage disconnect (LVD) systems installed on many trucks

To help prevent the main battery set from discharging too much in starting the truck.

What is the guided diagnostic software used by some engine manufacturers designed to do?

To isolate electrical, electronic, and mechanical problems in a systematic manner. Use it when it's available. 2. In most cases, this software is designed to rapidly source electrical and fuel system problems, and can additionally direct the technician to locate engine mechanical problems.

How many amps are current requirements of solenoids on some larger starters?

Upward of 100 amps, often necessitating a separate relay (also know as a magnetic switch) to handle the high amperage load.

How would you test starter circuit components?

Using the voltage drop method. (discussed in Task B.9. 2. This is the preferred method for determining the serviceability of cranking circuit components. 3. Obvious physical damage, such as cables with rubbed insulation or clamps with broken or cracked ends, warrants a replacement.

What is the best way to clean a battery?

With water and baking soda solution.

How would you perform the load test on a battery?

1. First determine the rating of the battery. This is usually expressed in cold cranking amps (CCA), although some older batteries might be rated in ampere-hours. (AH) 2. Draw the battery down with the load tester at a rate equal to one half the CCA or three times the AH. 3. Hold this load for 15 seconds. 4. At the end of 15 seconds, with the load still applied, note battery voltage. 5. A battery that passes at 10.7 volts versus one that passes at 9.7 volts is the better of the two. 6. One that barely passes will not last long. Keep this in mind in severe weather climates.

How would you perform a battery load test?

1. First determine whether the battery is fully charged. 2. If testing a partially charged batter, that condition is caused by charging system problems, it will fail.

After starting the engine of the booster vehicle, what should you do and look for?

1. If the jumper cables are of a generous size, crank and start the dead engine immediately. 2. If the cables are small, or youare using a fast boost charger, allow the connection to remain for a few minutes while the dead battery recharges. 3. Then, with the help of the booster battery, crank and start the engine. 4. Remove the cables in the reverse order of installation.

How would you inspect a battery?

1. Inspect the top of the battery case for a buildup of dirt and moisture that can cause a low amperage current draw across the top of the battery. 2. This can be checked by taking one probe of a DMM and dragging it across the top of the battery while holding the other probe on one of the posts. 3. Any significant reading indicates a low-current short between the two battery terminals, which can result in a low or dead battery over a period of time.

What problems are frequent with battery cables and the terminal ends? How can you test for the problems?

1. Many times they are the cause of a no start or a sluggish starting complaint. 2.A simple voltage drop test will quickly identify the connection(s) with excessive resistance.

If a fast charger is required, what precautions should be taken?

1. Never allow more than a 50-60 amp charge rate, and then monitor the electrolyte temperature to make sure it does not exceed 125 degrees F (51.67 C). 2. If the specific gravity reaches 1.225 during the fast charge, reduce the charge rate accordingly. 3. If gassing or spewing of electrolyte occurs, reduce the charge rate. 4. Never charge a frozen battery until it is brought up to room temperature.

What are the proper procedures for jump starting a dead battery?

1. Proper procedures must be followed to ensure that a spark is not generated that can cause an explosion. 2. A battery that is low due to prolonged cranking is likely generating explosive vapors near the vent caps and a spark at this location could be dangerous.

How do you test for voltage drop in the positive battery cable?

1. Set the DMM to the V-DC scale and attach one probe to the positive terminal post of the battery (not the cable or terminal). 2. Touch the other probe of the DMM to the starter solenoid stud (again, not the cable itself). 3. While holding the probes in this position, crank the engine until you get a steady reading. 4. Ideally, there should be less than a one half volt drop. 5. If the drop is greater than one=half volt, narrow the problem down by checking point to point along the cable (e.g. battery post to cable end, cable end to cable wire, wire end to wire end). 6. Ideally, each connection along the cable should have less than one-tenth of a volt drop. 7. Remember that polarity with a DMM is not important. 8. If leads are backward, the display will show a minus sign in front of the reading.

What is the key start switch and what does it do?

1. The key start switch is a low-current switching deice that controls the magnetic switch (relay). 2. Current from this relay goes to the starter solenoid (another relay) to engage the starter. 3. Both the control and light current circuits need to be in working order to get the engine to crank. Neutral safety switches are also sometimes found between the key switch and the magnetic relay. 4. They are designed to prevent an engine from starting in gear.

There are many causes of slow crank, no crank, extended cranking, or cranking noise conditions conditions. How would you determine whether the cause is related to the engine or the electrical cranking circuit?

1. The technician must evaluate whatever evidence is apparent by listening, checking that elecvtrical connections are no overheating, and observing smoke emission during cranking, that would indicate that fuel was being injected.

What two functions do most starter solenoids have?

1. They shift the starter drive pinion into mesh with the flywheel ring gear and 2. make the high current connection to deliver battery power to the starter motor field coils.

Why do vehicles with automatic transmissions use to connect the engine crankshaft to the transmission torque converter.

1. They use a flex plate. 2. This flex plate has a ring gear on the outer edge that performs the same function as the flywheel ring gear. 3. This flex plate and ring gear need to be closely inspected when servicing the starter or any of the transmission components in this area. 4. If the technician finds cracks in the flex plate, then the flex plate should be replaced.

What does manually barring an engine do?

1. Will quickly verify whether an engine is mechanically seized. 2. To manually bar an engine, the technician physically connects a large wrench to the engine. 3. This process allows the engine to be turned by hand.

What should you do when you are sure the battery is ready to be load tested?

1.Draw off the surface charge if the battery has just been charged by either an alternator or battery charger. 2.Load the battery by either cranking the starter for 15 seconds or drawing 300 amps with the load tester for 15 seconds. 3. Allow the battery to sit for a few minutes.

If a starter fails to crank and all the other circuits to the solenoid check our what should you remember?

That the set of electrical contacts in the solenoid are subject to pitting and corrosion over time.

Where is the module for the LVD system installed?

The LVD system is installed in series between the battery set and the truck power distribution center.

What is the cause if a starter pinion fails to engage the ring gear?

The cause could be a solenoid fault.

What are the disconnect and reconnect voltage volts?

The disconnect voltage is typically around 10.4 volts and the reconnect voltage is around 12.2 volts. These parameters can be changed, depending on the needs of the truck operator.