Follow up on the Ballast resistor issue

BlueRooster · #1 (**permalink**) 10-16-2011, 11:30 AM

Just a follow up question to "bug in the ignition" I replaced the BR when the car wouldn't start in the run position and it worked. I also noticed that the battery cutoff was burned out too. So I replaced that also. Car seems bulletproof, but I am wondering why it happened in the first place.

So...I parked the car at dusk and I left the headlights on for about 20 minutes. I did not think the lights would wear the battery down but I was wrong. I tried to push start it but it didn't work. A buddy then got out the jumper cables and the situation went downhill. The car immediately fires up, revs high then shuts down completely. The jumper cables get super hot and the car is completely dead. Something blew the Ballast Res' and blew out the battery disconnect switch. Luckily it didn't melt down the whole thing. Do you guys have any thoughts on why it happened and what can be done to make sure it doesn't happen again. I am now reluctant to jump it again(if it ever needs to be). I was thinking about a bad ground but everything seems OK right now. Where would this bad ground be? And why only during the jump?

patrickt · #2 (**permalink**) 10-16-2011, 11:50 AM

When you jumper, you're going POS to POS and NEG to NEG right? And the jumper cables are two separate cables that couldn't somehow be shorting across one another, right?

vettestr · #3 (**permalink**) 10-16-2011, 01:15 PM

A ballast resistor drops voltage from around 14.2 to 9.5 VDC to increase ignition component life. I does that by loading the circuit and consuming voltage but this voltage drop produces heat. A ballast resistor gets hot, hot enough to burn you pretty quick.

I will go out on a line here and guess you either had the key in the run position or some failure let the BR sit there and cook (worse if points happened to be closed) for 20+ min. You can bet the coil was hot as hell too. Check the coil for oil leaking out or a bulged case. I would carry a spare if it is not bad today.

Then the jumper cables tried to dump high amperage into a dead battery and you hit it with the big amps from the starter when she would crank over. Add maybe a poor connection internal to your bad disconnect switch. No surprises here.

BlueRooster · #4 (**permalink**) 10-16-2011, 08:34 PM

Patrickt: Of course.

vettestr: I read your response a few times and it all makes sense. The coil was not bulging and it does seem to be working. a backup is wise. I also now have a back ballast re'. As far as leaving the key in run; maybe between the push start and jump start. 20 min sounds about right. Note to self: Don't leave the key in run position.

vettestr · #5 (**permalink**) 10-17-2011, 10:05 AM

Glad you have her fixed and ready to go. An easy check of the ignition spark quality is just a visual check. The spark at the plug should be neon blue if all is at peak performance. A yellow color points to a coil and more of an orange spark leans toward condenser/coil weakness. The new electronics (MSD) replacing the condenser - contacts of the points -saturation time of the coil does skew this visual test but a crisp blue spark is still ideal.

Remove the easiest plug wire at the spark plug end. Install an old or extra plug in the removed wire and set it on a header tube so the electrode is visible and grounded. Start the engine and check the color. **** don't grab the wire when running or you will become the ground path !!! don't let it arc on a polished valve cover as it will mar the finish. A bit shade tree mechanics but shows you where to start looking and don't get shocked cause 20 to 60KV HURTS.

Tommy · #6 (**permalink**) 10-17-2011, 12:01 PM

Quote:

Originally Posted by BlueRooster

Note to self: Don't leave the key in run position.

A bit of trivia in case you didn't already know this. Cars built with mechanical points back before electronic ignitions had both ballast resistors AND ignition switches with one or more switch positions than modern cars. For example, my 1963 Corvette ignition switch has (from left to right): Accessories, Lock, Off, Run, Start. The Accessories position was to allow all electrical systems except the ignition to be powered. This was specifically intended to prevent overheating the ignition system components and burning the points if they happened to be closed when the operator wanted to sit and listen to the radio. Modern cars generally don't have the Accessories position because modern electronic ignitions don't have that problem. The fact that your car has a ballast resistor tells me you should either have an ignition switch with an Accessories position, or you should remember your note to self. .... BTW, most cars are wired to allow the headlights to operate without having the key on.