Mopar Mystery Part Everyone Loves To Hate

so we're picking through the wiring on our miata trying to figure out what's going to stay and what's going to go um we're going to wire this thing just like one of our older cars so this way everything's consistent use the same alternator and the same everything right uh but obviously a lot of this wiring is going to have to go because we're not powering that motor anymore uh and some of it's got to stay because we need the headlights and the wipers and all that to work and it's just it's a bit of a rat's nest i'm picking for it i'm like for some reason as i'm doing this right it popped over my head so i'll have the first miata on earth with a ballast resistor right the ballast resistor what what what an amazing little device and it's like the most misunderstood and maligned system in all of the traditional chrysler products because you know what most mechanics you know chrysler was the smallest of the big three you know they were in the minority so most mechanics used to working on gm cars were used to work on ford cars when a chrysler thing came along they found these little unorthodoxies and it drove them crazy but it's really the simplest thing in the world go over here now the concept of an ignition resistor is not unique to chrysler products any of the older cars that used an oil filled coil like this had some sort of resistor and even like for instance gm cars used a ballast resistor if you go back to the 1955 the the tri-five chevys had balanced resistors a lot of them had ballast resistors but as the error evolved they went to general motors and ford went to resistor wires okay that went from the ignition switch you know the key switch to the coil and the easiest way to identify a resistor wire from a regular wire is that instead of having copper strains the resistor wire has got silver strands so the purpose of the resistor wire is to keep the coil from overheating so as the engine is running and it's going through its rpm range and all the different cycles and whatnot the load the resistance inside the coil changes it varies and as it does you want to take some of the voltage away and then you have the wild card of the charging system so we always think of these things as 12 volt systems but they're not really 12 volt systems it's a 12 volt battery give or take right but the charging system is always above that the charging system will spike up to 15 and have 16 volts it'll settle down to around 13 and a half volts it's more than the 12. the resistor wire in the general motors and ford products well here's the difference between a resistor wire and a ballast resistor the resistor wire is a one trick pony in other words it's a fixed value what goes in versus what comes out so 12 volt goes in 10 volt comes out it gets to 14 volts 14 volts go in 12 volts go out the balance resistor is a always varying device it senses the load inside the coil and then reduces the amount of voltage going to the coil to reduce the heat and then when the heat dissipates or you know the load drops then the bowel system ballast resistor allows the voltage to rise back up again it's really that simple but they get blamed for everything okay the wipers don't work it's the ballast resistor the charging system doesn't work it's the ballast resistor it's blamed for everything but the only thing that the ballast resistor controls is the voltage going to the coil right or the voltage going to the ignition system so i have come over here so here on this 66 dart is the ballast resistor in its natural habitat they're always mounted someplace on the firewall they're always exposed because it's a heat it's a heat generating device um on these cars the early bodies are right in the middle of firewall later when they move them to that corner uh of the firewall b bodies have them in different places but all of the classic era chrysler cars have a ballast resistor there are two styles of ballast resistor there is this two pin and this is the one that was used on all points ignition systems right later on when they went to electronic they went to this style here so on this style two of these pins handle the load to the coil and the other two pins handle the load to the ecu uh you know it's not necessary that's what the old five pin ec the original version if you're converting to like a four pin ecu you don't have to worry about this you can use the single and you'll get along just fine so there's circuitry that's involved around the ballast resistor and this is one of the difference between chrysler and general motors and ford on chrysler there are two positions for the key right start and run when you're in the start position you get the full battery voltage directly to the coil so basically it bypasses the ballast resistor and the reason for that is because when you're cranking the motor especially like when it's cold right you crank on the motor it takes a lot of battery juice so you don't need you don't want that resistance you know the extra resistance going to the coil so basically in the crank position it's getting full 12 volt whatever whatever the battery has got as soon as the engine starts you let go of the key then it goes to resisted voltage so that's what those two positions on the ignition switch are on general motors and ford products that circuit that start circuit was handled for the starter solenoid that's where that extra post on the the the gm starter because you you've always got the three posts on the gm starter the big one that the battery wire goes to the small one that you know from the key that extra post is the one that's non-resistor the resistor bypass to the coil so how do you know one of these things go goes bad and the truth is they don't go bad as often as people would have you believe you'll always hear that cliche make sure you throw a balance resistor in the glove compartment i have cars that are almost 60 years old that have their original ballast resistors i've had exactly one of these things go bad in the last like 10 or 12 years since i started driving nothing but you know these cars i've only had one go band it was kind of recently one of the things you can do if you're concerned about that the battle physicists are dropping dead on you is if you're using this style with the two pins just hook up one of these instead so that if for some reason the ballast resistor the the two pins do go bad you can always just switch your wires over to the other ones and motor on down the road yes they do have different values but for the sake of getting you home they're fine and if you're dealing with this tile and it it blows you can just jump them out you'll be fine to go 20 30 50 miles to the house you're not gonna you're not going to melt down your ignition system because of it but they're they're that simple one other thing i want to go go over about this if you're using an aftermarket coil like i i love these these axle coils these things are just fantastic i've been i use them on everything that you know needs that extra these coils come with a ballast resistor they come with a separate ballast resistor even if your car has a ballast resistor already wired in right add the one that comes with the coil okay so in this case here we've got here's here's the uh here's the ignition feed from the switch okay and here is the ballast resistor it would be like the normal ballast resistor found on the firewall and then we jump from this with this wire here to this ballast resistor and then from this ballast resistor to the coil itself to power the coil now on the surface you say well you know two ballast resistors that's just way too much but remember they're load sensitive so it you're not you're not you're not taking you're not robbing any any voltage that's needed from the coil but when the coil does get hot you've got that extra backup resistor to soak up some of the extra voltage and let things cool down a bit that's it if your aftermarket coil comes with a ballast resistor put it in there you need it and also if you're converting a gm or ford car to an hdr style ignition make sure you don't use that resistor wire to fire the coil now because the non-oil filled coil does not need that resistance so make sure that if you're converting a general motors or a ford car to hei that you're not using that silver resistor wire make sure you've got a full 12 volt source from the ignition switch so how do you know if your ballast resistor has gone bad this is too easy it's too simple right no test equipment no test lights you don't need an old mirror you need it nothing you need nothing here's how you know if your balance resistor has gone bad crank the car if the engine starts as long as your key is in the run position but then stalls when you let go of the key it's the ballast resistor that's it that is the only symptom one of these things will ever give you so it doesn't get any easier than that that's why i love the old school stuff so that's it back to my rat's nest of wiring and i'll see you tomorrow

Channel: Uncle Tony's Garage

Views: 44,474

Rating: 4.9554849 out of 5

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Id: 5BWTaZ_AfH8

Length: 9min 54sec (594 seconds)

Published: Mon Apr 05 2021