This must be somewhat age related. My ride has not started in 10 years, and lives in an open carport with no battery in it. Last time I looked the goop was all down the firewall. Our hottest days (year-round) are in the mid eighties.
Electronic Ignition , Goop leaking out
- Thread starter JoeyL
- Start date
I'm not convinced that it's heat related. I've had brand new ones leak their potting resin inside their sealed box. I believe it's more of a chemical breakdown thing. Either way, it doesn't seem to affect whether they work or not. I've had leakers that worked great for years, if not decades.....and perfect looking ones that were bad.
JimmyG
Member
I can understand the personal feeling of satisfaction from "saving" a brain box after the resin turns to liquid. However, the electronics knowledge part of me can not help but wonder what damage those components may have received from exposure to high heat and moisture. That resin wasn't put there just to hold things together! It has also been my experience, that the components within the brain box are often times the source of the heat that caused the resin to run, lose integrity, or bubble. These very observations are the tell tale signs of a box that is about to die or that has already come to a life ending moment. Unless you have an undeniably strong reason to retain the original box for matching numbers or presentation reasons, there are plenty of replacements as well as methods available, to make them appear as if they were an original box. Just sayin'.
57fury440
Well-Known Member
What about a unit that has never been used and had the resin leak out. How would the internal parts be responsible for causing the leak?
JimmyG
Member
The reality is that we could speculate all day long. I agree with the statements of others before me, high heat storage is the most likely cause in an unused unit. We should also remember that there was a flurry of cheap offshore knockoff look alike boxes produced for several years. Who knows what quality of resin was in those. If you decide to replace it, go to a reputable Mopar aftermarket supplier and enjoy the ride.
Vaanth
New Member
Supplementing what's already been noted, the material you see is a potting compound. It is not melting, but is slowly breaking down and oozing out. Potting compound has been used for decades in electronics to seal for environmental protection against moisture, debris, etc. and movement of internal components from vibration, mechanical shock, etc. The compounds are typically fast curing two part or single component chemicals that form a solid or semi-solid protective barrier. Over time the compound can break down and "run" or otherwise deteriorate. Heat does not necessarily cause it, but can aggravate the breakdown.
Chrysler used semi-solid potting compounds in the electronic control units (ECUs), electronic voltage regulators, air conditioning high speed cutout controllers, EGR timers, and other similar electronic modules. In some ECUs and voltage regulators, sand was added to the compound as an additional stiffener for mechanical shock and vibration resistance.
1970s assemblies are more susceptible to the oozing than later production parts. Later production was changed to a more rubber-like or silicone-like compound that breaks down less. In general, the parts can continue to function with the compound leaking out unless affected by moisture or other factors. Aftermarket components can also suffer from similar breakdown depending on the nature of their compound.
When the early compound used by Chrysler oozes it forms a sticky mess. It can be dissolved with lacquer thinner, but it's tricky to remove from painted surfaces without risking the paint. I've successfully removed it with lacquer thinner from vehicles as well as ECUs and voltage regulators, including the internal areas. Removal from the internal areas does risk removing electronic component markings and weakening the components, especially the electrolytic capacitors. I have replaced the removed potting compound with two part (A-B) silicone or urethane compounds.
ECU replacement is not necessary due to the oozing, but when the internal components are uncovered, they could be affected by the environment. The ECU can continue to work though and not necessarily electrically fail due to the oozing.
In 50+ years of working with Mopars, I've only seen a couple or so of real ECU electrical failures on our own personal vehicles and maybe only two or three ballast resistor failures (all 4-pin). One single ballast resistor failure too, but that was an original resistor on a point system (1966 Belvedere 318 Poly in the late 80s). One ECU was the original that failed after 46 years. Almost none of the potting was left in it, but I have not looked further yet to see why it actually failed. Another was a Chrysler ECU with a "Mopar Remanufactured" sticker on it that came on my 1974 truck that I got in 1990. It failed about 10 years later. I have a Borg Warner ECU that is flaky. It works, but fires oddly, and triggers the coil without the engine running, but key on in "run".
Replacements of my own vehicle ECUs have mostly been due to potting issues, a "better" ECU, or a preferred different ECU, not functional failures. For potting issues, I re-work them to clean it up.
Here is an ECU that oozed on my Duster with bugs and other debris stuck in it and after cleaning the oozed potting off the car and re-potting the ECU:
I've done others. Cleanup difficulty varies depending on the extent and the mounting.
These are my ECU spares and some being re-worked for potting compound breakdown and oozing.
These all work, both Chrysler and aftermarket. Some I bought new years ago, some NOS later, some are used original Chrysler, and others are new aftermarket. None are newer manufacture than the mid 90s, so none are the newer cheap, inferior offerings without proper internal components. Several brands are here: Chrysler, Chrysler Direct Connection, Wells, Sorensen, Filko, Kem, Big A, Echlin, Standard/Elextron, Auto-Tune, Atlas, and Motorola.
These two ECUs were removed from cars in a field. Both are originals that Chrysler installed in the cars. One in 1974, the other in 1976. They both still work but will be cleaned up and re-potted.
These have had the potting removed.
The "de-potted" ECUs have been re-painted and tested, but not re-potted yet. I don't attempt to make them look original, just somewhat decently so. I might replace a sticker.
In addition to these, each of my 15 operating vehicles have Chrysler factory electronic ignition as installed, or added by me with other factory parts or Direct Connection/Mopar Performance kits. Each of those also carry a spare ECU in the trunk, although I've never had to use one on the road.
I can repair the ECU if needed depending on the fault, but removing the circuit board from the soldered connector pins and the main power transistor is a hassle. I've broken a capacitor in the potting removal and had to correct that. Actually, in 50+ years of working with Mopars, I've only seen a couple or so of real ECU failures on our own personal vehicles and maybe only two or three ballast resistor failures (all 4-pin). One single ballast resistor failure too, but that was an original resistor on a point system (1966 Belvedere 318 Poly in the late 80s). One ECU was the original that failed after 46 years. Almost none of the potting was left in it. Another was a Chrysler ECU with a "Mopar Remanufactured" sticker on it that came on my 1974 truck that I got in 1990. It failed about 10 years later. I have a Borg Warner ECU that is flaky. It works, but fires oddly, and triggers the coil without the engine running, but key on in "run". I've had two that were intermittent, one Direct Connection, and one Atlas. Replacements have mainly been due to potting issues, a "better" ECU, or a preferred different ECU. So, I have more spares than I likely will need, but if I see a good deal on a good NOS unit, I am tempted to grab it.
I can test an ECU or factory wiring with the factory tester. It's typically easier and more realistic though to just temporarily mount the ECU on a vehicle and start/run it for testing. For checking ECU wiring checking, I prefer a multimeter.
I converted one of my failed ECUs into a wiring junction box for experimenting with a semi-hidden MSD-6A with a stock electronic distributor to appear factory and to allow me to convert back to a stock ECU without re-wiring if needed. I saw no real benefit with the MSD other than maybe tolerating wider plug gaps better, so I removed it for stock. I experimented similarly with a Jacobs Ignition setup which showed more benefit, but I later went back to stock on that one too.
I'm doing similar rework on 1970+ voltage regulators and police air conditioning cutouts which can also suffer from potting breakdown and oozing.
FYI...
Chrysler used semi-solid potting compounds in the electronic control units (ECUs), electronic voltage regulators, air conditioning high speed cutout controllers, EGR timers, and other similar electronic modules. In some ECUs and voltage regulators, sand was added to the compound as an additional stiffener for mechanical shock and vibration resistance.
1970s assemblies are more susceptible to the oozing than later production parts. Later production was changed to a more rubber-like or silicone-like compound that breaks down less. In general, the parts can continue to function with the compound leaking out unless affected by moisture or other factors. Aftermarket components can also suffer from similar breakdown depending on the nature of their compound.
When the early compound used by Chrysler oozes it forms a sticky mess. It can be dissolved with lacquer thinner, but it's tricky to remove from painted surfaces without risking the paint. I've successfully removed it with lacquer thinner from vehicles as well as ECUs and voltage regulators, including the internal areas. Removal from the internal areas does risk removing electronic component markings and weakening the components, especially the electrolytic capacitors. I have replaced the removed potting compound with two part (A-B) silicone or urethane compounds.
ECU replacement is not necessary due to the oozing, but when the internal components are uncovered, they could be affected by the environment. The ECU can continue to work though and not necessarily electrically fail due to the oozing.
In 50+ years of working with Mopars, I've only seen a couple or so of real ECU electrical failures on our own personal vehicles and maybe only two or three ballast resistor failures (all 4-pin). One single ballast resistor failure too, but that was an original resistor on a point system (1966 Belvedere 318 Poly in the late 80s). One ECU was the original that failed after 46 years. Almost none of the potting was left in it, but I have not looked further yet to see why it actually failed. Another was a Chrysler ECU with a "Mopar Remanufactured" sticker on it that came on my 1974 truck that I got in 1990. It failed about 10 years later. I have a Borg Warner ECU that is flaky. It works, but fires oddly, and triggers the coil without the engine running, but key on in "run".
Replacements of my own vehicle ECUs have mostly been due to potting issues, a "better" ECU, or a preferred different ECU, not functional failures. For potting issues, I re-work them to clean it up.
Here is an ECU that oozed on my Duster with bugs and other debris stuck in it and after cleaning the oozed potting off the car and re-potting the ECU:
I've done others. Cleanup difficulty varies depending on the extent and the mounting.
These are my ECU spares and some being re-worked for potting compound breakdown and oozing.
These all work, both Chrysler and aftermarket. Some I bought new years ago, some NOS later, some are used original Chrysler, and others are new aftermarket. None are newer manufacture than the mid 90s, so none are the newer cheap, inferior offerings without proper internal components. Several brands are here: Chrysler, Chrysler Direct Connection, Wells, Sorensen, Filko, Kem, Big A, Echlin, Standard/Elextron, Auto-Tune, Atlas, and Motorola.
These two ECUs were removed from cars in a field. Both are originals that Chrysler installed in the cars. One in 1974, the other in 1976. They both still work but will be cleaned up and re-potted.
These have had the potting removed.
The "de-potted" ECUs have been re-painted and tested, but not re-potted yet. I don't attempt to make them look original, just somewhat decently so. I might replace a sticker.
In addition to these, each of my 15 operating vehicles have Chrysler factory electronic ignition as installed, or added by me with other factory parts or Direct Connection/Mopar Performance kits. Each of those also carry a spare ECU in the trunk, although I've never had to use one on the road.
I can repair the ECU if needed depending on the fault, but removing the circuit board from the soldered connector pins and the main power transistor is a hassle. I've broken a capacitor in the potting removal and had to correct that. Actually, in 50+ years of working with Mopars, I've only seen a couple or so of real ECU failures on our own personal vehicles and maybe only two or three ballast resistor failures (all 4-pin). One single ballast resistor failure too, but that was an original resistor on a point system (1966 Belvedere 318 Poly in the late 80s). One ECU was the original that failed after 46 years. Almost none of the potting was left in it. Another was a Chrysler ECU with a "Mopar Remanufactured" sticker on it that came on my 1974 truck that I got in 1990. It failed about 10 years later. I have a Borg Warner ECU that is flaky. It works, but fires oddly, and triggers the coil without the engine running, but key on in "run". I've had two that were intermittent, one Direct Connection, and one Atlas. Replacements have mainly been due to potting issues, a "better" ECU, or a preferred different ECU. So, I have more spares than I likely will need, but if I see a good deal on a good NOS unit, I am tempted to grab it.
I can test an ECU or factory wiring with the factory tester. It's typically easier and more realistic though to just temporarily mount the ECU on a vehicle and start/run it for testing. For checking ECU wiring checking, I prefer a multimeter.
I converted one of my failed ECUs into a wiring junction box for experimenting with a semi-hidden MSD-6A with a stock electronic distributor to appear factory and to allow me to convert back to a stock ECU without re-wiring if needed. I saw no real benefit with the MSD other than maybe tolerating wider plug gaps better, so I removed it for stock. I experimented similarly with a Jacobs Ignition setup which showed more benefit, but I later went back to stock on that one too.
I'm doing similar rework on 1970+ voltage regulators and police air conditioning cutouts which can also suffer from potting breakdown and oozing.
FYI...
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On your ECU tester, do you find it tests 4 pin ECUs correctly? While asking, what is best way to test Voltage regulator off car?
Vaanth
New Member
I have the C-4166-A tester. It tests 4-pin ECUs okay, but the Ballast Auxiliary Circuit light will indicate a fault, because the fifth pin for that is not there. The earlier C-4166 without the C-4166-1 adapter might not test correctly, but I have not used one of those. I haven't even used mine in a long time because I just test on a vehicle.
Similarly I test voltage regulators on the vehicle. Using all Mopar regulators, I rarely have one fail, and not one in the last 20 years or so. But if I have an unknown I temporarily connect it on a vehicle to test.
Testing an electronic 1970 or later off the car can be done as follows:
- Use a variable voltage, current limiting DC (direct current) power supply capable of a DC voltage range of ~0 volts to
~20 volts, and a current range of ~0 amps to ~2 amps.
- Current limit the power supply to 3 amps.
- Set the voltage to 0 volts.
- Connect the negative/ground lead of the power supply to the case of the regulator.
- Connect the positive lead of the power supply to the "center" terminal on the regulator to which the "Ignition Run"
connects. The connected wire is typically blue in passenger cars and red in trucks.
- Using a voltmeter set to read between 0 and 20 volts, connect the negative lead to the regulator case and the positive
lead to the "side" terminal on the regulator to which the field wire connects. This field wire is typically green on cars but
can differ on trucks.
- Begin ramping the voltage up on the power supply while watching the voltmeter. The voltage will vary on the voltmeter,
but follow power supply applied voltage.
- When the power supply reaches 13.5 to 13.8 volts, the voltmeter should drop to zero. This indicates that the regulator
is driving the field lead to ground to energize the alternator field.
- Continue ramping up the voltage on the power supply while watching the voltmeter. At at about 14.3 to 14.5 volts, the
voltmeter should indicate some voltage. This indicates the regulator is releasing the field ground and indicated voltage
will drift up.
Alternatively, a test lamp could be connected between the two terminals connections and it should light when the field connection is driven to ground by the regulator. Lamp loading might affect the test a little. There could be other testing arrangements as well.
Note: Wire colors mentioned can vary across models and years.
Note: Temperature compensation is designed into Mopar regulators and good aftermarket regulators, so regulation voltage varies depending on temperature (IE. more when colder, and less when hotter). Also production variances can affect numbers. The Direct Connection/Mopar Performance regulator, # P3690731 does not use temperature compensation and operated at a fixed constant voltage of 13.5 volts.
Note: this connection setup is for the 1970 and later "Isolated Field" alternator electronic voltage regulator. The 1969 only "Insulated Brush" alternator electronic voltage regulator (# 2875400) has three terminals. In addition to the ignition run and field terminals, it also has a suppression lead and the connections differ. In this case the suppression should be connected to a 12 volt source with a shared ground, although it might work by tying the suppression lead to the ignition run. However, I have not tested one of these.
If I was mass testing regulators, I would set this up, but I find it is simpler to test on the car to see if regulation occurs for just one or a few.
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Neat info on testing them. I know the FBO boxes explicitly say that their ECUs cannot be tested as it may cause permanent damage to the components...but a part of me wonders if that's just to protect intellectual property or trade secret sort of things, basically, I'm wondering if it's possible to completely disregard their warning about testing it and test it anyway. Lol.
Vaanth
New Member
After I wrote up the power supply and voltmeter method for bench testing electronic voltage regulators, I remembered a simpler method. If available, use the Chrysler tool for it, Miller C-4133 Voltage Regulator Tester. I forgot that I have one:
The procedure for the tests is outlined in the factory service manuals. This image is from a 1973 manual:
The procedure describes testing on the car (disconnected from the car wiring), but it works the same on the bench.
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Just what I have been looking for. No luck yet.
Vaanth
New Member
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