ballast resistors

[moparjohnny]

anyone knows what makes a ballast resistor go bad? what is the function of the ballast resistor?i hear more people saying that they have a bad resistor than people use to say back in 1960 era,are people adding more stuff on these cars in terms of accessories or are the resistors poorly made now. back in 60 era people were not talking about the stuff we hear a lot of now such as dash fires,car not cooling down the way it should,to much power going thru amp meter,that little 37 amp alternator seem to be sufficient to handle everything back then, i know we live in a new age now,but i wonder if we are not out smarting our selves with adding all these new accessories which might require those big alternators and cause to rewire different components,maybe walter p chrysler and the dodge brothers would like to see these cars remain as simple as they made them,sorry guys just venting. back to main question on ballast resistors. thanks

 

[A383Wing]

it takes heat to cut down the voltage from in to out on the resistor...the more resistance, the more heat is generated by the resistor...

it's heat that destroys them

and the resistor only controls the power to the coil, nothing else...alternator and all those other accessories have nothing to do with it

 

[patrick66]

When a ballast resistor goes tits-up, your car will refuse to start. Age and heat are generally the culprits. Have you stuck a spare on the car to verify that is the problem?

 

[moparjohnny]

no patrick this was just a exploritory question for future reference i will be using one though.

 

[patrick66]

Gotcha.

 

[GetX'd]

Is a ballast resistor something you should have a spare lying around? Can you still get them at your local parts stores. Mine is literally 47 years old. Never been changed - but the cars been in storage for 35 years. What do you suggest?

 

[Matrix2]

When you crank the engine, the ballast resistor is bypassed, so the coil sees the full battery voltage. The coil cannot tolerate this for long, so when the car is running, the ballast resistor reduces the voltage to the coil. If you jump (or remove) the ballast resistor, you will burn out the coil (try it, see what happens!).

 

[GetX'd]

Questions above still stand - ???? Don't want to be caught unprepared.

 

[Bb70charger500]

Always keep a spair there cheap .
They are poorly made now I've had good luck with the AutoZone brand for lasting the longest.
The heat kills them nothing else .
You can buy at any parts store or online (rock auto,eBay,ect)
My advice is leave yours on till it quits but keep a spair (a lot come with life time warranty) I keep a spair ballistic,a voltage reg ,and a set of points and condenser. In my glove box at all times .
I also keep a spair alt,starter,control module,valve cover gaskets and ignition switch (elc side) in the garage on the shelf since I have muti cars running the same parts all with life time warranty so when it brakes I switch with the in stock part then go trade in the bad one (most of the time they have to order the parts in)
Now you don't need every thing I keep but I would strongly suggest the first set because these parts just don't last .

also to answer your other ? The reason why these cars over heat and so on is people that don't know how the car works go in and "upgrade it" 99% of the time do more harm then good .
A 440 stayed at a perfect temp with its stock rad and fan/fan shroud setup when people go in and change stuff and then say my car runs hot even after they installed a huge aluminium rad why? Well they leave out fan shrouds (witch are very important) or they changed the fan to little pissy elc fans that would normally cool a 4 cly Honda well yeah it's going to run hot .

Unless it's done right .

So to answer your ? In short the problem is people that have no clue .
Hope I was helpful

 

[GetX'd]

Thx Bb70 charger - just what the Dr. ordered. I appreciate your very helpful post.

 

[Mr Gorsky]

Be careful of the new aftermarket ballast resistors.

I fitted one that was arse about. Had been built with the 5 ohm resistor in the .5 ohm slot.

Measure them with a meter before fitment.

 

[terzmo]

napa...autozone...advance auto all have them...beware of scammers charging crazy prices for "platnum" resistors....keep a spare

 

[Moparsmitty]

Resistors burn out for basically the same reason as incandescent light bulbs. Any conductor that has enough voltage running through it to create heat will eventually burn out. You can bypass a resistor in an emergency, but like the guys here say, it's not good for the coil (or the points if you still have them) and will eventually cause them to fail. It's a good idea to carry a spare ballast resistor.

 

[GetX'd]

My mechanic says my car doesn't need a ballast resistor because we're running an MSD electronic ignition - no points. It's the ready to run, plug n play no need for the 6AL box.

I thought based asked on above comments that the ballast was to protect the coil and the points. I get the no points - but obviously the car still has a coil.

Am am I missing something?

 

[A383Wing]

what coil are you running GetX'd?

if it's internally resisted, then you don't need the ballast resistor....if it's not, then you need the resistor....

 

[GetX'd]

I'm running the MSD Blaster coil. Is that internally resisted? The Summit specs say resister included. I don't know if that means inside or if they give you resister with the coil as a separate part???? Thx

 

[dave5237]

Is a ballast resistor something you should have a spare lying around? Can you still get them at your local parts stores. Mine is literally 47 years old. Never been changed - but the cars been in storage for 35 years. What do you suggest?

I was told you want a 1.0 ohm ballast resister for my orange box set up on my GTX. You want to make sure you get the right one. You can check the ohm with a multi meter. I always carry a spare one in my glove box.

 

[GetX'd]

I don't have a box - none needed for a ready to run MSD ignition. Do you still need a resistor for the coil only? The coil doesn't have a built in resistor. MSD Blaster II.

i know I might seem a little thick on the subject - but my mechanic tells me one thing and I don't want to have an unpleasant surprise because he's wrong. The car is not being driven since the new motor install - and won't be til resto is finished. It's just started occasionally and would heat up the coil enough to blow it.

sorry for the redundancy but the validation is appreciated. thx

 

[Endangered Species]

With the newer coils I don't think you need a ballast Resistor. Back in the 80's my 66 Dodge Monaco kept going through ballast resistors. Finally I got pissed when it stranded me, so I by passed it to get me home and never looked back. At the time I was running a Accel coil.

 

[383man]

You dont need a ballast resister when running MSD ign. In fact most MSD units hook both of the coil primary wires right to the MSD control box so even if you left the ballast in the car it wont be going to the coil any more. On MSD you get a multi-spark below so many rpms and thats one reason the MSD unit controls the primary pos and neg wires to the coil. The MSD control unit can limit the current through the coil by how long it lets the coil saturate (coil grounded) as its not like points that are mechanically fixed to open and close at the same place all the time which turns the coil circuit on and off and it dont have to worry about the points burning. The electronic boxes can wait a few milliseconds before grounding the coil after it fires if needed to control coil magnetic field build-up. Most electronic ignitions dont use a ballast as GM stopped using its resister circuit when they went to HEI ign in the 70's as it feeds the full 12 volts to the coil and module.

Most dont know that up until about 1973 when Ford and GM cars also had points the Ford and GM cars also had a resistance in the coil primary circuit but they used a resistance wire in the wire harness instead of a ballast resister and it was also bypassed when the eng was cranking. Also the ballast resister like Mopar uses can change its resistance by the heat in it. At idle when the eng is running slow the coil stays grounded longer and it heats the resister more to add resistance but at higher speeds when the eng is running faster the coil dont have time to be grounded as long and it makes less heat in the ballast so it cools a little and lets more current through at higher eng speeds.
But if you look at the instructions that comes with MSD ing it will tell you they do not need a ballast resister. Just use the MSD blaster coil thats made to work with the MSD and it will work fine. Ron