Ballast Resistor- how hot is too hot?

[gtx6970]

Five cents worth.... (exchange rates are brutal)

Now that was funny.

 

[Bee1971]

It’s Hot Out , Really Hot - Post #62

 

[twecomm]

As Mom always said... Don't touch the ballast resistor, you will burn your finger !!!

 

[dadsbee]

All this bullshit over electrons moving from one atom to the next. Post 64...

 

[Kern Dog]

Be careful..
Testing an ECU is a challenging task...
Its key component is the power transistor

I agree. I had hoped that this manual would have been a little more detailed in that :

The only test I could find pertains to this:

To test, I grounded the case. I then attached the probes to #5 pin, then battery ground on this unit:

This ECU was pulled from my Charger last night when the car wouldn’t start. It actually showed .2 ohms when I tested it today.





In the Duster, it started and idled but popped and stumbled when I revved it up. I can only imagine how it would be in gear out on the road.

A power transistor can have what called "secondary breakdown" and its internal silicon shorts out under current/voltage load..

If I am understanding this right, this means a failing component can work under light load but fail under higher load? If so, that is what seemed to happen here.
No offense to others here but I want to be better than I’ve been in the past. The habit of swapping parts until something works feels like the work of the guy that doesn’t know what to do. I want to be able to diagnose better.
If I didn’t have 10 ECUs, numerous ballast resistors and coils to swap around, I’d be at the parts store buying stuff to fix something that wasn’t broken.
The blue “Hi Rev 7500” ECU failed last month. It had proper grounding but conked out at the exact same time the ballast resistor failed. Is it possible that one led to the other? If so, why? Did the dying ECU burn up the ballast or did intermittent failures from the ballast cook the ECU?
Nothing about my combination is unusual. I run a stock based alternator that shows a 13.5+ charge according to the volt meter. The battery is in the trunk. I am well grounded at all points. The only Piccadilly about this car is the occasional failures in the ignition system.

 

[Sinitro]

I agree. I had hoped that this manual would have been a little more detailed in that :

View attachment 1717562

The only test I could find pertains to this:

View attachment 1717563

To test, I grounded the case. I then attached the probes to #5 pin, then battery ground on this unit:

View attachment 1717564

This ECU was pulled from my Charger last night when the car wouldn’t start. It actually showed .2 ohms when I tested it today.

View attachment 1717565

View attachment 1717566

In the Duster, it started and idled but popped and stumbled when I revved it up. I can only imagine how it would be in gear out on the road.



If I am understanding this right, this means a failing component can work under light load but fail under higher load? If so, that is what seemed to happen here.
No offense to others here but I want to be better than I’ve been in the past. The habit of swapping parts until something works feels like the work of the guy that doesn’t know what to do. I want to be able to diagnose better.
If I didn’t have 10 ECUs, numerous ballast resistors and coils to swap around, I’d be at the parts store buying stuff to fix something that wasn’t broken.
The blue “Hi Rev 7500” ECU failed last month. It had proper grounding but conked out at the exact same time the ballast resistor failed. Is it possible that one led to the other? If so, why? Did the dying ECU burn up the ballast or did intermittent failures from the ballast cook the ECU?
Nothing about my combination is unusual. I run a stock based alternator that shows a 13.5+ charge according to the volt meter. The battery is in the trunk. I am well grounded at all points. The only Piccadilly about this car is the occasional failures in the ignition system.

As I posted previously secondary breakdown is a common failure mode with bi-polar power transistors..
In a power transistor with a large junction area, under certain conditions of current and voltage, the current concentrates in a small spot of the base-emitter junction. This causes local heating, progressing into a short between the collector and emitter. Same basic issue happens frequently for power transistors used in audio power amplifiers,(home & car) especially when the device is heated up and driven hard. Power transistors that are rated @ higher voltage/current are more expensive, but today with outsourcing from China they typically strive to use a lower rated power transistor to save $$. Also I mentioned in previous posts, my primary vocation for many years was sourcing consumer electronics from the Orient for certain major USA clients, typical average annual value of exports exceeding $100 million per year. So I have 1st hand experience sourcing, last year just for an excercise I requested a price quote for a Mopar ignition module(comparable to the orange box) from a known major Chinese source that builds & supplies ignition modules. Their quote was $4 in quantities of 250 pieces, note that 250 pieces is considered a small order and the price will drop significantly under $4 as the quantities are increased...

Just my $0.02...

 

[twecomm]

Now that everyone has burned our fingers feeling our ballast resistors... Seems the conversation has morphed to ignition (ECM) boxes. Take a look on E-Bay just to see the wide variety of ECM's being sold. Search "Mopar electronic ignition box". Many different manufacturers, many different colors, different brands of the large transistor seen on the front. That large silver color transistor is the device that actually switches the coil on and off mimicking what the points in the distributor in the pre electronic ignition days. Just looking a one page of items for sale, I saw at least 4 different names of vendors. From what I could make out from the pictures, the transistors have markings of 7 different part numbers from 4 different manufacturers such as RCA, ST Semiconductor, SGS Semiconductor with what appears to be all "house" part numbers rather than JDEC part numbers and many with no markings at. all. Who knows who made it, what you might actually be buying or what you actually already have. Just carry a spare.

 

[hunt2elk]

You need to find one of these rigs Greg.

 

[HALIFAXHOPS]

Those testers work well on the car just hard to find a working one now. Biggest issue I have found with ecu/s are how many are made like junk overseas. This link we beat the hell out of them.

1974 Brain Box saves the day.

Was heading out to a local car gathering a couple weeks ago, and a no start on my '76 Truck. Turns out the 1 year old replacement brain box failed. I had a well used 1974 5 pin brain box from my '74 Dart that I had replaced because all the goo on the back had melted out from the hot sun in...

www.forabodiesonly.com

Then real and fake differences.

How to tell a "fake" ECU from a real one

There are a ton of fake ecu's out there two easy wats to tell at a glance are the height of the transistor, usally the fake ones are around 3/8" high and a real one 5/16 or so. Another way to tell at a glance is if there is printing on the...

www.forabodiesonly.com

 

[HALIFAXHOPS]

I agree. I had hoped that this manual would have been a little more detailed in that :

View attachment 1717562

The only test I could find pertains to this:

View attachment 1717563

To test, I grounded the case. I then attached the probes to #5 pin, then battery ground on this unit:

View attachment 1717564

This ECU was pulled from my Charger last night when the car wouldn’t start. It actually showed .2 ohms when I tested it today.

View attachment 1717565

View attachment 1717566

In the Duster, it started and idled but popped and stumbled when I revved it up. I can only imagine how it would be in gear out on the road.



If I am understanding this right, this means a failing component can work under light load but fail under higher load? If so, that is what seemed to happen here.
No offense to others here but I want to be better than I’ve been in the past. The habit of swapping parts until something works feels like the work of the guy that doesn’t know what to do. I want to be able to diagnose better.
If I didn’t have 10 ECUs, numerous ballast resistors and coils to swap around, I’d be at the parts store buying stuff to fix something that wasn’t broken.
The blue “Hi Rev 7500” ECU failed last month. It had proper grounding but conked out at the exact same time the ballast resistor failed. Is it possible that one led to the other? If so, why? Did the dying ECU burn up the ballast or did intermittent failures from the ballast cook the ECU?
Nothing about my combination is unusual. I run a stock based alternator that shows a 13.5+ charge according to the volt meter. The battery is in the trunk. I am well grounded at all points. The only Piccadilly about this car is the occasional failures in the ignition system.

First hi rev I have heard of fail. Yes the ecu if internally shorted will blow the ballast like a fuse. Biggest thing with any ignition is to have the matching parts, Ballast resistors at the parts store do not list how many ohms kind of a crap shoot there. Here is an example of matching. Do not run the HP on the street with those ballast, they are designed to cool off between 1/4 runs.

 

[RJ Squirrel]

I have read this whole thread and still dont know how to get a high resistance woman hot

 

[HALIFAXHOPS]

Qualude CHRYS# p1cu812

 

[Bee1971]

I have read this whole thread and still dont know how to get a high resistance woman hot

Especially with one that has bi-polar secondary break downs

 

[BigJLaboski]

When wires and paint melt, that's when you know its too hot. I never did see the answer. Juat burnt my finger. So, now im here. Lol. Yep,,! old Jay is still learking!!!