Sunday, December 11, 2011

How To Test and Replace Ballast Resistor in Car?

First read this to Know what exactly is Ballast Resistor.
The process of starting a car involves more than simply turning the key to fire up your engine. Between the battery and the starter, a ballast resistor helps regulate the voltage.
A resistance element in series with the primary circuit to reduce the voltage supplied to the coil during engine operation.
A ballast resistor helps regulate voltage flowing in an electrical system to avoid overloads or battery drainage.
When a distributor has mechanical breaker points, a resistor is needed to keep the points from burning prematurely.
A ballast resistor is also used on many early electronic distributor ignition systems.
Some automobiles use a resistance wire in the ignition system instead of a ballast resistor.
Now first inspect Ballast resistor.
  • The resistance value of most ballast resistors is usually between 0.8 and 1.2 ohms.
  • A ballast resistor consists of a resistible element encased in a ceramic block assembly.
  • The assembly should be checked for scorching or cracks.
  • Also check for broken or loose terminals and wires.
If Any problem noticed,then test Ballast resistor.The details are as follows :-----

  • Measure the resistance of the primary (ballast) resistor with an ohmmeter.
  • Remember, the key must be off when this test is performed or power in the circuit damages the meter.
  • In the ignition system shown below, ohmmeter leads are connected at the battery terminal of the coil and the wiring harness connector wire that join the red wire in the ignition module connector.
  • Compare the resistance reading to specifications.

There is a sample help diagram shown below.Refer the diagram for better understanding.

If the Ballast Resistor is tested/inspected faulty then replace it.Its not very hard to replace Ballast Resistor.The Basic details are as follows :----
1) Disconnect the wires from the assembly.
2) Unbolt the assembly from its location.
3) The resistor is usually in a ceramic housing bolted to the engine firewall, inner fender, or on the ignition coil strap.
4) Be sure to install the new resistor in the correct position to avoid damaging electronic components.
5) Torque the bolts to specifications.
Connect the wiring harness.


This details will help you.
If you need dis-assembly or replacement instructions for any other auto/car part, or you want to ask question related to your car/truck jeep problem then please leave the comment with your details, so I can provide you the required instructions and solutions.

For more car related problem troubleshooting:---

This are the sections, you can go through and click the link to read its troubleshooting.


The car will not start?


Car will not crank?


Car has no spark?


How to troubleshoot car battery?


How to test starter solenoid?



How to test cars starter?


How to replace starter in car?


car will turn over but will not start?


Car wont start?


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