A ballast resistor is a device in your vehicle that limits the amount of current in an electric circuit. The ballast resistor is commonly found in older vehicles, because they did not have the benefit of circuit boards found in most of today’s vehicles. Over time, the ballast resistor can be damaged by normal wear and tear, so there are a few things to look for when you suspect a bad or failing ballast resistor needs servicing.
Vehicle starts, then immediately dies
The most obvious symptoms will be the vehicle starts, but then immediately dies as soon as you release the key. If this happens, the professionals at YourMechanic will be able to measure the voltage coming from the ballast resistor and determine if you need a replacement. Once they read the voltage, they will let you know what condition your ballast resistor is in.
Not starting at all
If the ballast resistor is not working properly, the vehicle will not start. Since it is an electrical system, it is something best left to the professionals to handle. The only way to have the vehicle up and running again is with a ballast resistor replacement.
Don’t jump the resistor
Some people try to jump the resistor, which means you bypass the ballast resistor and the extra current goes to the points. The points are not designed to take this extra voltage, which causes them to wear out and fail prematurely. This will give you a much more extensive repair than if you had the ballast resistor replaced in the beginning. Furthermore, it can be dangerous, especially if you don’t know what you are doing, because you are messing with electricity.
Let the vehicle be
If your ballast resistor is bad, your vehicle will not run and you will have to have it towed to the mechanic’s shop. By using the professionals at YourMechanic, you will be able to cut down on towing costs because they make house calls. In addition, since the vehicle will not start, it is not a dangerous situation as long as you let the vehicle be. Do not try to bypass the ballast resistor and do not keep trying to start the engine. Let the professionals fix it so you can be on your way.
The biggest sign your ballast resistor is bad is your vehicle will start, but immediately stop as soon as you let go of the key. If you suspect you need a replacement, be sure to see a professional mechanic.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Ballast Resistor and was authored by Ed Ruelas.