Hi I've now changed the ballsast resistor on the car twice, and they don't seem to last for too long. I know the last two I've gotten haven't been the correct ones since we couldn't figure out which one to use. The guy at autozone suggested one for a charger and I said fine, 2.99$ doesn't hurt that bad. Does anyone know which one to use for this engine, or how does this work? After a couple of months the car can't start, it sounds like it's trying to fire on one or two cylinders, then you cange the ballast resitor, and the car fires right up. I've read that you won't need a ballast resistor if you get an electronic ignition system installed, is it worth doing that instead? I saw one on ebay for 70$, but if I get the right ballast resistor would the problem go away? Many thanks in advance
I do not know about 72 models but 70s do not use one as the resistance on the primary side of the coil is built in to a calibrated length of wire. Are you sure it calls for one on a Centurion?
I think the coil should get something like 9 volts to it if the wire is doing its job. It would be interesting to probe the wire with a DVOM and see what voltage you have with the car in running condition vs the bad one in place.
I'm with Jim here- my first thought was "you sure you have one?" My early '70 Skylark definitely doesn't...things like this don't seem to have been 'downgraded' on our cars...Chevies and Mopars come to mind as notorious ballast resistor cars, not '70s Buicks o No:
Agreed, it didnt come that way from the factory. I just assumed that the resistance wire might have been cut out and a ballast resistor put in its place. Might have been a local gas station butcher job fix at one time? As you know, alot can happen to a car in 30 years. Kimson...take a picture of it so we can see what your talking about. That might help clear this up.
If it has a ballast resistor spliced in...that makes me dount the rest of the forward harness is right I'd want to double check on voltage regulator and alternator numbers if an aftermarket ballast resistor has been installed I have found some wacky things on my car, but luckily most gas station guys were too chicken to start messing with the ignition :grin: Th e whole reason I started doing my own work whenever I could was that most pro 'exprets' don't know squat about old cars and use hearsay and their best guesses on old iron...not a knock on anybody, but the pros I have talked to about right and wrong on my car...I don't know If one's been right yet. I can't even tell the stories, not even room on the forum...engine, body, rear end, suspension, frame...all incorrect according to one pro or another. And yet...the chassis manual says it's right. Who should I beleive? Kimson, I suggest that you track down your new best friend- a 1972 Buick All Series Chassis Manual. the you'll know, for sure, what's right or wrong for your car
I went out and took some pictures of what the setup looks like. I'm not sure where the skinny green cable hooked up to one end of the ballast resistor connects to in the fuse box, but I sure would like to know The black cable attached at the other end goes to the positive side on the solenoid. I've also heard somewhere before that my car shouldn't have one of these installed so that is most likely correct. What is the reason for someone installing one of these? Also, anyone ever had a look at the back side of one of these fuse boxes? Is it a "no go" area, or can it be sorted out? Many thanks for the help guys :TU:
Looks like the resitance wire was removed for some reason and a ballast resistor was put in its place to step the current down (you cant run 12 volts direct to the coil). Lets start off by checking your powers and grounds. Take a reading from a digital volt ohm meter of the voltage at the positive side of the coil with the ignition "on" and tell us what it is. Also take a reading of the voltage before the resistor. To make sure it's battery voltage. Also make sure there is no voltage present when the key is in the "off" position. Jason
The only reason for a ballast resistor/ clibrated wire is to drop the voltage down to 9 volts for the points. You can run 12 Volts but you'll be changing points out every few months. If you replace the points you can forego the ballast all together. Get a new coil to work with 12V and increase your spark gap to .040. I'm certain you'll feel a great improvment in thottle response with such a change. I did. That's just what I'd do.
Kimson, Let me explain how the factory system works. Stock,there is a calibrated length of resistance wire(1.8 ohms), that comes out of the firewall connector(under the brake booster). At some point in the harness, it is joined by a plain copper wire from the "R" terminal on the starter solenoid, which then extends to the + side of the coil. When you are cranking the engine to start, battery voltage is supplied directly from the "R" terminal to the coil. When the engine starts, and the key springs back to the run position, voltage no longer is supplied at the "R" terminal. Voltage is supplied to the coil through the firewall connector, through the resistance wire, and on to the coil. If your resistance wire was taken out, you can use a ballast resistor(get one as close to 1.8 ohms as possible) Run a wire from the "R" terminal of the starter solenoid, and tee it in after the ballast resistor, then to the coil. You'll get full battery voltage while cranking, for a fast start. Then voltage will be cut down by the ballast resistor, to maximize your point life. With the engine off, and the key in the run position, voltage at the + side of the coil should be 5.5-6 volts. Now disable the ignition(pull the coil wire at the distributor cap) Crank the motor. Voltage should jump to at least 9 volts at the + side of the coil. Someone must have removed your resistance wire. It comes out of the firewall connector. look for a clipped off wire there. The firewall connector comes apart, and you can replace the wire. It clips in to the connector with a special barbed clip that you can reuse. Good luck. BTW, this is what that special barbed clip looks like. Once you separate the firewall connector, all the wires clip into the front side with this type of clip.
Larry, it's amazing how many times you answer this question per week. (Including for me.) Thank you very much. Maybe this should be a sticky! Frank
