Various Flaws Can Start an Auto Fire

Times Staff Writer

Question: So often on the radio, there are reports of auto fires on the freeways. Will you please explain the cause of these fires and what a motorist can do to keep a car from catching fire?--B.W.

Answer: Next to a major accident, a fire is the most likely event to totally destroy your car, so complete is the damage to the body and electrical system.

In the city of Los Angeles, the fire department handles about 40 car fires each week. The majority of them, however, do not occur on freeways. In fact, most of the fires are the result of theft, according to Los Angeles fire investigator Jack Jakubowski.

After they finish stripping a car, thieves will often torch it either for kicks or to destroy evidence. These arson fires are easy to detect because of telltale burn patterns.


Leaking Gasoline

You might think that leaking gasoline is a major cause of car fires, but fuel-system leaks are seldom responsible. Manufacturers usually pay close attention to fuel systems for the very obvious reason that gasoline is so explosive.

The fires that occur on the freeway are generally caused by catalytic converters that overheat, according to Jakubowski. The converters overheat while a car is idling in a traffic jam, igniting the carpeting on the interior.

Some car-care experts say another major cause of automobile fires is missing air cleaners. Some motorists remove air cleaners once they become clogged and try to save money by not replacing them. The lack of an air cleaner allows the engine to backfire, throwing explosive gasoline back into the engine compartment.

Car fires are caused by many other problems. Brake systems can overheat on trucks, electrical systems can short out, and careless smokers can allow cigarette embers to fall onto upholstery.

Accumulated oil and grime on an engine can help fuel an under-hood fire. You may be able to reduce the severity of a car fire by keeping the engine clean, but you probably will not be able to prevent a fire.

Often enough, a motorist doesn’t even know he or she has a fire in the engine compartment until the paint starts melting and bubbling on the hood. That’s when it’s time to pull over and make a prompt and probably final exit from the car.

If you do have a fire, be careful. Do not throw open the hood, because the additional oxygen may cause the fire to virtually explode in your face. If you do have a fire extinguisher, you should try to direct it into the wheel wells or under the car. Obviously, you would want to call the fire department as quickly as possible and then your insurance company.

Q: Can one check the output of an automobile charging system with a voltmeter across the battery posts?--C.R.D.

A: A voltage meter on the battery posts will tell you whether the charging system is putting out adequate voltage when the motor is running, but not whether it is generating adequate electrical current to keep the battery charged.

If the charging system, which includes the alternator and voltage regulator, are operating correctly, you should read about 13.6 to 14.8 volts. If the voltage is below that, you most likely have a problem. But at the same time, even if your voltage is correct, you may still have a problem.

You need to check the output of the system with an ammeter. Newer ammeters are inductive, meaning you can simply attach a clamp to the outside of the battery wire to get a reading. The older style ammeters required them to be wired in series with the battery. The ammeter should register a moderate charge going into the battery.

Test the Battery

One last step in a charging system check is to test the battery to ensure that it has a sufficient charge to start the car. This again involves voltage and current tests. Sometimes, batteries can put out adequate voltage but cannot store much electrical current.

Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.