Nacho-RT74
Well-Known Member
some are isolated from environment temperature getting the rear groove full sealed with the epoxy filler on back making the resistor not visible
Ballast Resistor on our 69 GTX - Requesting Feedback
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Dave6T4
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Use the one on the left with original points distributor. Use the one on the right for electronic distributor. I think the failed ballast resistor was a myth invented by Chevy guys. LOL. I have been driving Mopars for almost 60 years, and have never replaced one. That being said, I still carry a spare in the glove compartment! LOL.
Nacho-RT74
Well-Known Member
True… I never have got any ballast failed either
About the application of the non sealed ballast… this is a rear view of a dual ballast (elect ign)
But the sealed resistor is for the side feeding the ECU (5 ohms)
Althought both sealed are available too
About the application of the non sealed ballast… this is a rear view of a dual ballast (elect ign)
But the sealed resistor is for the side feeding the ECU (5 ohms)
Althought both sealed are available too
Last edited:
Vaanth
Well-Known Member
FYI....
Regarding ballast resistor differences, specifically with the rear exposure or not of the resistor, Chrysler changed the resistance and thermal interaction of ballast resistors twice, which include the presence of the filler, or lack thereof.
With the introduction of the four terminal, dual ballast resistor with electronic ignition in late 1971, the primary, or compensating, side of the dual resistor used with the ECU is the same type as the earlier point systems resistor, part number 2095501, et.al. with an open back, ceramic housed, wire wound nominal 0.55 ohm resistor. The resistor still performed the same thermal adjusted coil current/voltage stabilization as with the point ignition system. The resistor also limits the current through the power transistor of the ECU, protecting it, similar to the same action with points.
The other side of the ceramic case dual ballast resistor houses an enclosed "non-thermal" auxiliary resistor which measures 4.75 - 5.75 ohms at 70-80 degrees Fahrenheit. This nominal, five ohm resistor is connected to the "fifth pin" of the electronic control module (ECU). Internal to the ECU, the auxiliary resistor connects to the collector lead of the driver transistor for the main power transistor and part of its biasing. It limits overall current from the 12 volt supply.
This dual ballast resistor is Chrysler part number 3656199 and was used from late 1971 until mid 1975. In later 1975 production, Chrysler adjusted the primary resistance in the dual ballast resistors to 1.25 - 1.5 ohms and also encased the resistor in a ceramic compound with similar thermal properties to the resistor body, reducing the thermal action as part number 3874767. The effect of current limiting based on engine speed and temperature variation was lessened to a shorter effective range. Although the actual resistance specification changed, much of the literature specification did not.
In 1980, Chrysler revised the five pin ECUs to remove the external auxiliary resistor connected to the fifth pin of the ECU. The external resistor function is included internally in the revised internal circuitry. The new two terminal ballast resistor (part number 4106140, 5206436, et.al.) is 1.25 ohms ( 1.12-1.38 ohms ) for the primary circuit to the coil. The new ballast resistor eliminated the metal bracket and had a mount molded into the ceramic housing. Compared to the pre-electronic 2095501 "thermal" resistor, the new resistor had less thermal interaction.
These changes provided a more stable, albeit less flexible, effect of thermal heating and cooling and resultant changes in current flow to the coil primary through the ECU switching transistor. With electronic ignition, the lesser range of resistance/temperature/current variation was not an issue. The total potential delivered spark energy at minimum resistance between the "non-thermal" and "thermal" resistance is less, but was a compromise, and negligible in ignition system performance in a production vehicle.
Running the earlier points resistor or the earlier dual ballast resistor in place of the comparable later versions can provide total more potential delivered spark energy available for enhanced tuning with a non-stock engine, as well as added RPM potential depending on the ECU.
The following images show the front, back, and part numbers close up of the "thermal" and "non-thermal" four terminal dual ballast resistors for comparison:
The following image shows the back up of the points ignition "thermal" ballast resistor and the later electronic ignition "non-thermal" resistor for comparison:
Over the years, the distinction between the resistors, particularly the dual ballast resistors, became less definite and in many cases became none. Variations, supersessions, substitutions, applications differences, tolerance differences, different valuations, and specifications in the aftermarket, and even with Chrysler, blurred the distinctions. For the later single ballast resistor, Chrysler specifies it with different values depending on the source, such as 1.25 ohm, 1.5 ohm, and even at 1.0 ohm for part number 5206436 and P5206436.
The aftermarket might build the package with variations that do not follow original construction such as shown in the following image:
The differences with the filler compound, in general, point to the difference in thermal and non-thermal function of the resistor and its effects. It can also provide visible evidence of differences in the resistor types, but not always, especially with the later the manufacture occurs in relation to when the original applications were still fresh.
For more information about Chrysler’s electronic ignition, including ballast resistors, and their use with other components, refer to
Chrysler Electronic Ignition
Regarding ballast resistor differences, specifically with the rear exposure or not of the resistor, Chrysler changed the resistance and thermal interaction of ballast resistors twice, which include the presence of the filler, or lack thereof.
With the introduction of the four terminal, dual ballast resistor with electronic ignition in late 1971, the primary, or compensating, side of the dual resistor used with the ECU is the same type as the earlier point systems resistor, part number 2095501, et.al. with an open back, ceramic housed, wire wound nominal 0.55 ohm resistor. The resistor still performed the same thermal adjusted coil current/voltage stabilization as with the point ignition system. The resistor also limits the current through the power transistor of the ECU, protecting it, similar to the same action with points.
The other side of the ceramic case dual ballast resistor houses an enclosed "non-thermal" auxiliary resistor which measures 4.75 - 5.75 ohms at 70-80 degrees Fahrenheit. This nominal, five ohm resistor is connected to the "fifth pin" of the electronic control module (ECU). Internal to the ECU, the auxiliary resistor connects to the collector lead of the driver transistor for the main power transistor and part of its biasing. It limits overall current from the 12 volt supply.
This dual ballast resistor is Chrysler part number 3656199 and was used from late 1971 until mid 1975. In later 1975 production, Chrysler adjusted the primary resistance in the dual ballast resistors to 1.25 - 1.5 ohms and also encased the resistor in a ceramic compound with similar thermal properties to the resistor body, reducing the thermal action as part number 3874767. The effect of current limiting based on engine speed and temperature variation was lessened to a shorter effective range. Although the actual resistance specification changed, much of the literature specification did not.
In 1980, Chrysler revised the five pin ECUs to remove the external auxiliary resistor connected to the fifth pin of the ECU. The external resistor function is included internally in the revised internal circuitry. The new two terminal ballast resistor (part number 4106140, 5206436, et.al.) is 1.25 ohms ( 1.12-1.38 ohms ) for the primary circuit to the coil. The new ballast resistor eliminated the metal bracket and had a mount molded into the ceramic housing. Compared to the pre-electronic 2095501 "thermal" resistor, the new resistor had less thermal interaction.
These changes provided a more stable, albeit less flexible, effect of thermal heating and cooling and resultant changes in current flow to the coil primary through the ECU switching transistor. With electronic ignition, the lesser range of resistance/temperature/current variation was not an issue. The total potential delivered spark energy at minimum resistance between the "non-thermal" and "thermal" resistance is less, but was a compromise, and negligible in ignition system performance in a production vehicle.
Running the earlier points resistor or the earlier dual ballast resistor in place of the comparable later versions can provide total more potential delivered spark energy available for enhanced tuning with a non-stock engine, as well as added RPM potential depending on the ECU.
The following images show the front, back, and part numbers close up of the "thermal" and "non-thermal" four terminal dual ballast resistors for comparison:
The following image shows the back up of the points ignition "thermal" ballast resistor and the later electronic ignition "non-thermal" resistor for comparison:
Over the years, the distinction between the resistors, particularly the dual ballast resistors, became less definite and in many cases became none. Variations, supersessions, substitutions, applications differences, tolerance differences, different valuations, and specifications in the aftermarket, and even with Chrysler, blurred the distinctions. For the later single ballast resistor, Chrysler specifies it with different values depending on the source, such as 1.25 ohm, 1.5 ohm, and even at 1.0 ohm for part number 5206436 and P5206436.
The aftermarket might build the package with variations that do not follow original construction such as shown in the following image:
The differences with the filler compound, in general, point to the difference in thermal and non-thermal function of the resistor and its effects. It can also provide visible evidence of differences in the resistor types, but not always, especially with the later the manufacture occurs in relation to when the original applications were still fresh.
For more information about Chrysler’s electronic ignition, including ballast resistors, and their use with other components, refer to
Chrysler Electronic Ignition
Last edited:
oldchevelle541
Well-Known Member
Thanks to everyone for your input. Always wondered why some aftermarket had a filler vs no filler. My GTX will remain a single point original setup moving forward so having an open back will be my way to go. I just liked to see if there is anything noticeable when you flip it around like my photo showed on Feb. 1. The dark discoloration on the one end may be nothing but to me it meant switching it out.
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Similar experience. Driving original Mopars since 1969, I never replaced one. My second to last GTX (restored), I had to replace both coolant temperature sensor and ballast resistor. I had the spare resistor in the glove compartment. I'm chalking it up to today's crummy electrical parts.
@HALIFAXHOPS just had some for sale. Let me see if I can find his ad.
oldchevelle541
Well-Known Member
Yes, I have communicated with him. He has a few laying around but something came up that put a pause on my project.
Some Car Guy
Well-Known Member
I had one fail in a 71 cuda…in the parts store parking lot. Enough talk about it led me straight to it and since I was there, lol, it was a nothing burger. I have had multiple voltage regs fail. Including one resto flat pack electronic style that exploded the filler out of the back. Kinda a mess.
Since I ditched the lints, I no longer need one, it’s jumped. I do carry a reg in my road kit.
Since I ditched the lints, I no longer need one, it’s jumped. I do carry a reg in my road kit.
