Ballast Resistor- how hot is too hot?

[NHCharger]

As stated, how hot is too hot? I checked my 69 Charger (440) tonight. After 10 minutes of idle it was up to 220º. On my 72 Charger (318) after 10 minutes at idle is was 442º. I checked the wires connected to the ballast resistor and they were only 100º. I took is for a spin and when I came back it was down to 230º. According to the FSM at low speed the ballast resistor will heat up, and at higher speed will cool off. However the FSM doesn't give any range on what is acceptable.

 

[R413]

Hotter than you think is normal.

Don't burn your finger and keep driving.

 

[MWbirdLOVER70]

Hotter than you think is normal.

Don't burn your finger and keep driving.

I hear that and learned how hot lol

 

[Geoff 2]

I am not sure there has ever been a temp specified that is too hot....

 

[kiwigtx]

A resistor by nature sheds heat as a biproduct of the circuit.

 

[twecomm]

Don't be concerned about the temperature. If you are, carry a spare in your glove box, that aren't expensive and easy to replace in the very unlikely event of failure. These are "wire wound" resistors with ceramic housings. They are designed to deal the current load of the coil and WILL get hot. The metal bracket that attaches it to the firewall helps conduct some of the heat to the firewall.
In the trunk of my 66 Charger you will find: LED flashlight, screwdriver assortment, basic wrenches, pliers & channel locks, spare coil, resistor, orange ECU box, fuses, paper towels and waterless hand cleaner. Most important, a small analog multimeter and roll of quality duct tape.

 

[NHCharger]

Thanks for the replies guys. I was concerned it might damage the paint on the firewall. Was considering installing a spacer between the firewall and resistor, but according to twecomm, the firewall helps dissipate the heat.

 

[RJRENTON]

As stated, how hot is too hot? I checked my 69 Charger (440) tonight. After 10 minutes of idle it was up to 220º. On my 72 Charger (318) after 10 minutes at idle is was 442º. I checked the wires connected to the ballast resistor and they were only 100º. I took is for a spin and when I came back it was down to 230º. According to the FSM at low speed the ballast resistor will heat up, and at higher speed will cool off. However the FSM doesn't give any range on what is acceptable.

How hot is too hot is a rhetoric question.....it's similar to the question: how high is up or why is there air? WHY DOES IT MATTER? Perhaps this query should be posed to our resident "trivial expert", specialising in totally inconsequential and useless information, who, cannot resist comments on anything/everything.....like installing a limiter plate in a distributor, Lithium batteries (amps vs amps), tire valve stem cap torque, soldering aluminum, ...... Mr. If I don't comment, I'll explode......Kern Dog.......which he'll likely do an documented expose, complete with temperature vs resistance vs amps vs ambient temp......let's see how long it takes......
BOB RENTON

 

[Sinitro]

The ballast resistor will definitely heat up but..
However is it the right resistor to match the coil and other ignition components including the ECM and distributor.
As many will recall I have posted multiple times..
Many of the reported ignition issues are due to the mismatch of various brand components..
An ignition system with mismatched components may work but for How long?

Just my $0.02...

 

[RJRENTON]

The ballast resistor will definitely heat up but..
However is it the right resistor to match the coil and other ignition components including the ECM and distributor.
As many will recall I have posted multiple times..
Many of the reported ignition issues are due to the mismatch of various brand components..
An ignition system with mismatched components may work but for How long?

Just my $0.02...

You are correct about mix matching components......but there are certain people that think "they know better" or their buddy's next door neighbor's Uncle Waldo ALWAYS uses a brand X coil.....a classic example of of the expression: "Caledonia, what makes your head so hard (stupid)"...does it anyway then ******* when the system fails.....amazing....
BOB RENTON

 

[Sinitro]

You are correct about mix matching components......but there are certain people that think "they know better" or their buddy's next door neighbor's Uncle Waldo ALWAYS uses a brand X coil.....a classic example of of the expression: "Caledonia, what makes your head so hard (stupid)"...does it anyway then ******* when the system fails.....amazing....
BOB RENTON

Hmmm..
My take is that many users don't understand the importance of matching each component thinking things can be openly exchanged. They may think all coils or ballast resistors are generic and equal...
Nuff said..

Just my $0.02 ..

 

[kiwigtx]

cannot resist comments on anything/everything

Resisting comments builds up a great source of heat.

 

[Kern Dog]

Hmmm..
My take is that many users don't understand the importance of matching each component thinking things can be openly exchanged. They may think all coils or ballast resistors are generic and equal...
Nuff said..

Just my $0.02 ..

That is a fair assessment.
As I have stated before, I've been lucky in life and sometimes, stuff works for me when it should have failed. I've stumbled though many situations that could have gone bad but my luck saves me from trouble.
I didn't know about compatibility of components. Many times, I put stuff together and when it works, I just think that I did it right.
I know this annoys SOME people.
I'm not fearless but I do have a tendency to jump into things that I don't know much about and find my way through it....sometimes alone, sometimes with the help of others. It is my nature to wonder, to try new things and to ask around if anyone else has done the same thing. I don't understand why someone would belittle a guy that is just doing his thing and sharing his encounters with others. If my comments bother you, feel free to scroll on by.

 

[451Mopar]

Worst case scenario (maximum ignition circuit current) for ballast resistor (and ignition coil) is when the ignition is on and the engine is not running (when the ignition points are closed, or with the factory type ECU which grounds the coil when there is no trigger signal.) In this steady state you just have the DC resistance of both the Coil and ballast resistor.
When the engine is running, the coil charging and discharging lowers the current because of the coils impedance.
Electrical impedance - Wikipedia

 

[moparsaver]

How hot is too hot is a rhetoric question.....it's similar to the question: how high is up or why is there air? WHY DOES IT MATTER? Perhaps this query should be posed to our resident "trivial expert", specialising in totally inconsequential and useless information, who, cannot resist comments on anything/everything.....like installing a limiter plate in a distributor, Lithium batteries (amps vs amps), tire valve stem cap torque, soldering aluminum, ...... Mr. If I don't comment, I'll explode......Kern Dog.......which he'll likely do an documented expose, complete with temperature vs resistance vs amps vs ambient temp......let's see how long it takes......
BOB (ANGRY AT THE WORLD) RENTON

 

[MWbirdLOVER70]

How hot is too hot is a rhetoric question.....it's similar to the question: how high is up or why is there air? WHY DOES IT MATTER? Perhaps this query should be posed to our resident "trivial expert", specialising in totally inconsequential and useless information, who, cannot resist comments on anything/everything.....like installing a limiter plate in a distributor, Lithium batteries (amps vs amps), tire valve stem cap torque, soldering aluminum, ...... Mr. If I don't comment, I'll explode......Kern Dog.......which he'll likely do an documented expose, complete with temperature vs resistance vs amps vs ambient temp......let's see how long it takes......
BOB RENTON

We’re all friends here and try to help. Kern’s a friend so I value his input as well as yours and others. If that was a disrespectful comment not cool but if not ok. Just trying to keep the site civil -Rick

 

[MWbirdLOVER70]

That is a fair assessment.
As I have stated before, I've been lucky in life and sometimes, stuff works for me when it should have failed. I've stumbled though many situations that could have gone bad but my luck saves me from trouble.
I didn't know about compatibility of components. Many times, I put stuff together and when it works, I just think that I did it right.
I know this annoys SOME people.
I'm not fearless but I do have a tendency to jump into things that I don't know much about and find my way through it....sometimes alone, sometimes with the help of others. It is my nature to wonder, to try new things and to ask around if anyone else has done the same thing. I don't understand why someone would belittle a guy that is just doing his thing and sharing his encounters with others. If my comments bother you, feel free to scroll on by.

Kern your spot on and since 16 before going to tech school it was trial and basis and friends who had similar expirences. I’m like you and now 61 but love info and challenges. You my friend have great write ups and stories. A person I respect and call a Mopar Brother

 

[eldubb440]

in other words........ Bob didn't know the answer

 

[eldubb440]

That is a fair assessment.
As I have stated before, I've been lucky in life and sometimes, stuff works for me when it should have failed. I've stumbled though many situations that could have gone bad but my luck saves me from trouble.
I didn't know about compatibility of components. Many times, I put stuff together and when it works, I just think that I did it right.
I know this annoys SOME people.
I'm not fearless but I do have a tendency to jump into things that I don't know much about and find my way through it....sometimes alone, sometimes with the help of others. It is my nature to wonder, to try new things and to ask around if anyone else has done the same thing. I don't understand why someone would belittle a guy that is just doing his thing and sharing his encounters with others. If my comments bother you, feel free to scroll on by.

pretty sure hanging an entire front clip without as much as a tape measure would make his head explode

 

[RJRENTON]

View attachment 1712372

The question was: "WHY" is there air.......not "WHAT" is air.....big difference.....beside semantics.......btw....do you know the ACTUAL composition of air?.....or the actual weight of air?......it varies depending on temperature and density (barometric pressure) plus a few other factors....excluding solids and pollutants.......
BOB RENTON