leon bee Posted January 29, 2016 Share Posted January 29, 2016 I realize this is a general automotive question, and I've been googling already to try and learn about it. I'll keep doing that. I have some basic electrical skill, but don't understand if the resister is supposed to limit voltage or current, amps, what? I mean, can I tell anything with my multimeter? Engine running, or not? This is all complicated for me by the fact I'm looking at a lot of "desperation" type wiring I did 35 years ago. But once you learn about a failed resister in original wiring, not something you're likely to forget. So, I have another new good resister in there now. Car, 53 nailhead, is starting and running well as of yesterday. I just don't know if the resister is doing it's job. Any advice, THANKS!! Link to comment Share on other sites More sharing options...
SpecialEducation Posted January 29, 2016 Share Posted January 29, 2016 I realize this is a general automotive question, and I've been googling already to try and learn about it. I'll keep doing that. I have some basic electrical skill, but don't understand if the resister is supposed to limit voltage or current, amps, what? I mean, can I tell anything with my multimeter? A resistor is used to reduce the voltage - or electrical pressure - in a circuit. That said, as resistance goes up, amperage - or current flow - goes down. So, yes. Both. If the car has a 12 volt electrical system, but you have a device, say an ignition coil, that is designed to operate on 9 volts (I'm speaking hypothetically as I don't know the particulars of a '53), then you need a resistor that will dissipate 3 volts in heat energy. If the resistance is too high, you won't get enough voltage through the coil. If the resistance is too low, you'll get too much and burn up the coil. Typically, when a resistor fails, it burns out or fails open - like a light bulb in a string of old school Christmas lights. No voltage gets through the circuit at all. With the key on, you should be able to put a volt meter across the lugs of the resistor and make note of the voltage drop across the resistor. Then you should be able to put your volt meter across the coil (or blower motor, or whatever is downstream) and make note of voltage drop there. Those two numbers should add up to your battery voltage. That resistor is on a big chunk of ceramic to help it dissipate the heat. It should get warm in normal operation. 2 Link to comment Share on other sites More sharing options...
Ttotired Posted January 29, 2016 Share Posted January 29, 2016 The resistor can get burning hot, dont touch it Voltage checks will tell you, but the points need to be closed to complete the circuit before you start checking, otherwise your readings are going to show almost no change throughout the circuit Hard to get decent readings with the engine running as the pulses (and dirty electrical flows and spikes ect) tend to p*ss off a lot of multi meters and the readings will alter with rpm fluctuations anyway Another good test to see if its working is, if you are 100% sure your ignition is going through the resistor, start the car, is it running? Yes, its working, No, nup, its busted Mick Link to comment Share on other sites More sharing options...
leon bee Posted January 31, 2016 Author Share Posted January 31, 2016 I guess if I just make sure power is only getting to the coil through the resister, while the engine is running- after starting- I'll be okay. Link to comment Share on other sites More sharing options...
old-tank Posted January 31, 2016 Share Posted January 31, 2016 If it is wired correctly, full power only goes to the coil when the starter solenoid is energized. That's why cars with a defective resistor will fire but die as soon as the starter quits cranking. Look at the wiring diagram in your service manual.Willie 1 Link to comment Share on other sites More sharing options...
leon bee Posted February 1, 2016 Author Share Posted February 1, 2016 Thanks Tank: That's the part I learned under a burning hot Kansas sun many years ago. Kinda sticks with you. Mainly I was wondering if with my multimeter I could figure out exactly what's going to the coil. I'm moving on to something more fun, rotted floorboards. Link to comment Share on other sites More sharing options...
Guest dave5088 Posted February 7, 2016 Share Posted February 7, 2016 One side of the resistor should measure battery voltage, the other side 8-9 volts. This is key ON, engine OFF. You can also measure resistance across the resistor and see if its correct. Manual will say how many ohms Also, running full battery voltage all the time does not hurt the coil, but rather, the points. Modern cars with electronic ignition run full voltage all the time. No burned coils. They can do this because there are no physical contact points. Anyhow, if it runs then the resistor is most likely good. Link to comment Share on other sites More sharing options...
old-tank Posted February 7, 2016 Share Posted February 7, 2016 One side of the resistor should measure battery voltage, the other side 8-9 volts. This is key ON, engine OFF. You can also measure resistance across the resistor and see if its correct. Manual will say how many ohmsAlso, running full battery voltage all the time does not hurt the coil, but rather, the points. Modern cars with electronic ignition run full voltage all the time. No burned coils. They can do this because there are no physical contact points.Anyhow, if it runs then the resistor is most likely good.Systems that run 12v with no resistor have coils rated for 12v. Resistor systems have coils rated for the voltage after the resistor. Resistor systems only run 12v through the coils during starting. Running 12v continuously will burn the points and shorten the life of the coil. In fact prolonged cranking will shorten the life of the points...after adding an electric fuel pump to prime the carb before starting gives me up to 30,000 mile out of a set of points. Running electronic conversions like Pertronix at a full 12v will burn the rotor (burn as in catching fire inside the distributor) on a 55 Buick.Willie Link to comment Share on other sites More sharing options...
60FlatTop Posted February 7, 2016 Share Posted February 7, 2016 I remember a determined little old lady who got her Valiant to the shop with a bad ballast resistor. We heard her coming.Bernie 1 Link to comment Share on other sites More sharing options...
leon bee Posted February 7, 2016 Author Share Posted February 7, 2016 I remember a determined little old lady who got her Valiant to the shop with a bad ballast resistor. We heard her coming.BernieI know exactly what you are describing. Link to comment Share on other sites More sharing options...
buick man Posted February 9, 2016 Share Posted February 9, 2016 (edited) …with the Pertronix II setup, after tossing the points and condenser and installing the magnetic ring and module an air gap range of .010 & .060 must be maintained so using shims can stabilize this range. The original ballast resistor is tossed. With this system you will have consistent dwell regardless of rpm ranges. So achieving the proper air gap under the OEM rotor is essential. Edited February 9, 2016 by buick man (see edit history) Link to comment Share on other sites More sharing options...
old-tank Posted February 9, 2016 Share Posted February 9, 2016 …with the Pertronix II setup, after tossing the points and condenser and installing the magnetic ring and module an air gap range of .010 & .060 must be maintained so using shims can stabilize this range. The original ballast resistor is tossed. With this system you will have consistent dwell regardless of rpm ranges. So achieving the proper air gap under the OEM rotor is essential.David, the Pertronix unit on a 55 is different and does not work the way you described. Never, never leave the ballast resistor out on a 55. Link to comment Share on other sites More sharing options...
Ttotired Posted February 9, 2016 Share Posted February 9, 2016 The need for a ballast resistor on an aftermarket or electronically modified distributor is entirely dependent on how it was made and what coil you use Most electronic style ignition systems use a full 12V system, and do not need a ballast, but a 55 being a 6V system, I dont know (never fitted one to a 6V car) Mick Link to comment Share on other sites More sharing options...
Smartin Posted February 10, 2016 Share Posted February 10, 2016 55 is 12 volt Link to comment Share on other sites More sharing options...
old-tank Posted February 10, 2016 Share Posted February 10, 2016 The electronic system is just a switch that replaces the points which is also a switch and has no bearing on the rest of the system: coil, ballast, wires, plugs. With any "switch" that you use on a 55, use a stock coil with a ballast resistor if using the stock distributor, cap and rotor. Link to comment Share on other sites More sharing options...
60FlatTop Posted February 10, 2016 Share Posted February 10, 2016 At this point I'm happy with the points.I can't see the point of switching to the other type of switch. If I did switch I'd go with a crankshaft sensor, a couple of 4 cylinder ignition modules and 8 coils. Like that croc hunter said "Now that's a switch."Bernie 1 Link to comment Share on other sites More sharing options...
Ttotired Posted February 11, 2016 Share Posted February 11, 2016 Yep, 55 BUICK is 12V, 55 PLYMOUTH is not, my bad I am active on a mopar forum as well The reason that you change the coil to 12V on an electronic system is that the electronics are (normally) designed to run on 12V I wont say that they are ALL designed that way, but personally, I havnt seen one (used to put lots of kits in when I was an apprentice), so best advice is to follow manufactures instructions (A real man only does this when nothing works, wife is on your case and your at the point of calling someone else in thats going to laugh at you) The coil output voltage on an electronic system is higher than a points system purely because of the "clean" switching that is achieved with a transistor I wont go into depth, plenty of stuff on the WWW if you really want to work out its operation, but its advisable to change the rest (leads rotor, cap) when a conversion is done and its better to get heavier plug leads if you can, just because of the higher voltage Mick Link to comment Share on other sites More sharing options...
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