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Still chasing cause for failing points and condenser

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Still chasing cause for failing points and condenser

 
Old 06-12-2019, 10:24 PM
  #21  
6D2148
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Are the points burn't and look dark blue.

Chip
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Old 06-12-2019, 10:29 PM
  #22  
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Originally Posted by RickDett View Post
I ran two more tests


1. A reading at the "S" on the starter once the engine was running. I get .015 volts I assume that's virtually the same as zero. That's correct, and that's what should be happening.


2. Another reading with the single red power wire removed from the alternator. I get 9 volts at the positive coil down from 10.6 volts while the engine is at idle. That makes sense. It's an averaged voltage reading of a pulsing waveform. It was higher earlier (when the alternator was supplying 14+ volts to the ignition circuit)), and now it is running off of 12-13 volts out of the battery. There should be lower primary current at this lower average voltage.


RIck
Just curious, have you monitored/measured the voltage at the sensing voltage wire at the alternator (while it's running)? Looking at my repair book it looks like it's the red wire at the regulator connector.
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Old 06-12-2019, 10:41 PM
  #23  
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All I can say is that if you are producing 10.6 volts at the top end of the resistance wire and frying points, the first thing I would check is the alternator output. The resistance wire either works or it doesn't at all unless you have some modifications.
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Old 06-12-2019, 11:25 PM
  #24  
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Originally Posted by RickDett View Post
I'm not sure I follow you, could you reword or further explain?

Rick
Yep. Give this a try.

During normal engine operation the ignition system runs off of alternator voltage (13 or 14 volts), with a ballast resistor between the alternator voltage and the coil to limit the current (not voltage!) that goes through the coil and points. An ignition coil gets its energy charge-up by the amount of current that goes through it, not by any particular voltage that happens to be across it. During normal driving, with 13-14 volts pushing current through the ballast resistor, everything is hunky-dory for the ignition system. The problem occurs when you try to start your engine in 10-20 degree winter weather, when the oil is like maple syrup and your battery has lost a lot of its chemical energy due to the cold temperature. When you start cranking the engine over with these challenges, the current drain from the battery easily drops the voltage to 10 or 8 or 6 volts. At these lower battery voltages, there is going to be noticeably less current going through the coil to charge it up, and deliver it to the spark plugs. To get the current (not voltage!) back up to an acceptable amperage, the ballast resistance needs to be "taken out" of the picture. This is done by the R terminal of the starter solenoid. When the solenoid is activated during cranking, the solenoid not only kicks the starter gear into the flywheel ring gear, the solenoid also shorts out/connects the battery lug at the solenoid to the R terminal of the solenoid. This then supplies battery voltage (6 or 8 or 10 volts) directly to the R terminal, which is connected by a wire to the coil C+ terminal, feeding battery voltage directly (essentially shorting or shunting the ballast resistor's effect). This temporary (only during cranking) circuit compensates for low battery voltage during cranking, allowing correct/desired coil primary current and spark plug energy delivery.
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Old 06-13-2019, 12:17 AM
  #25  
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Can you post pictures of the failed points?


Originally Posted by RickDett View Post
Not sure what the difference is between primary, secondary or ignition resistance, but the wire from coil to firewall (all disconnected including at the “R” on starter) I get a reading of 1.6 ohms.

Is this an acceptable reading?

Maybe I should change out the alternator??

Rick

1.6 ohms is higher than the factory specification which should be easier on the points then the stock resistance specification.

Using your resistance measurements, the currents though the coil with a system voltage of 14.4V vs 13.5V are approximately 4.6A vs 4.3A. There is a 0.3A or 7% difference between these currents. I highly doubt a 7% increase in coil current is the difference between the points failing rapidly vs them lasting for 10's of thousands of miles.

Your alternator is fine. There is nothing wrong with the charging voltage you measured.


Originally Posted by RickDett View Post
Coil measures 1.5 ohms, secondary windings 9.09 ohms
The primary and secondary resistances in the table Peterbuilt posted are the coil resistances. Did you mean 1.5 ohms and 9090 ohms?

Personally. I would try another coil.
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Old 06-13-2019, 12:33 AM
  #26  
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Have you tried replacing your coil yet? Your secondary coil resistance seems low, according to this article:

http://www.superchevy.com/how-to/cor...gnition-coils/

I put 12000 hard miles on a Pertronix Ignitor, with a bypassed resistor wire, and wouldn't hesitate to do it again if I needed to preserve the look of a points system. I'd politely suggest switching to HEI, though. You don't still run bias-ply tires, right, so why not benefit from slightly newer technology in other aspects of the car?
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Old 06-14-2019, 05:17 PM
  #27  
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Originally Posted by 6D2148 View Post
Are the points burn't and look dark blue.

Chip

Burn't/pitted yes, Dark blue I don't think so but because they failed with less then 10 miles so I doubt.

Originally Posted by 69427 View Post
Just curious, have you monitored/measured the voltage at the sensing voltage wire at the alternator (while it's running)? Looking at my repair book it looks like it's the red wire at the regulator connector.
No but I will.

Originally Posted by CanadaGrant View Post
The resistance wire either works or it doesn't at all


Originally Posted by RickDett

I'm not sure I follow you, could you reword or further explain?

Originally Posted by 69427 View Post
Yep. Give this a try.

During normal engine operation the ignition system runs off of alternator voltage (13 or 14 volts), with a ballast resistor between the alternator voltage and the coil to limit the current (not voltage!) that goes through the coil and points. An ignition coil gets its energy charge-up by the amount of current that goes through it, not by any particular voltage that happens to be across it. During normal driving, with 13-14 volts pushing current through the ballast resistor, everything is hunky-dory for the ignition system. The problem occurs when you try to start your engine in 10-20 degree winter weather, when the oil is like maple syrup and your battery has lost a lot of its chemical energy due to the cold temperature. When you start cranking the engine over with these challenges, the current drain from the battery easily drops the voltage to 10 or 8 or 6 volts. At these lower battery voltages, there is going to be noticeably less current going through the coil to charge it up, and deliver it to the spark plugs. To get the current (not voltage!) back up to an acceptable amperage, the ballast resistance needs to be "taken out" of the picture. This is done by the R terminal of the starter solenoid. When the solenoid is activated during cranking, the solenoid not only kicks the starter gear into the flywheel ring gear, the solenoid also shorts out/connects the battery lug at the solenoid to the R terminal of the solenoid. This then supplies battery voltage (6 or 8 or 10 volts) directly to the R terminal, which is connected by a wire to the coil C+ terminal, feeding battery voltage directly (essentially shorting or shunting the ballast resistor's effect). This temporary (only during cranking) circuit compensates for low battery voltage during cranking, allowing correct/desired coil primary current and spark plug energy delivery.
Thanks I'll have to read it a couple times, once I get it I get it. But color animated charts would help next time. Ps My son is in his 3rd out of 5 years w/ Drexel as an electrical engineer student (currently interviewing for his 3rd co-op) so I’ll have him make the charts. Lol

Originally Posted by lionelhutz View Post
Personally. I would try another coil.
Thats next.

Originally Posted by Bikespace View Post
Have you tried replacing your coil yet? Your secondary coil resistance seems low, according to this article:
http://www.superchevy.com/how-to/cor...gnition-coils/

You don't still run bias-ply tires, right, so why not benefit from slightly newer technology in other aspects of the car?
No bias tires for me but I sure would like high octane leaded gas back.

Rick
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Old 06-14-2019, 05:17 PM
  #28  
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On another note as I mentioned I have a high amp alternator I also have a high-torque starter again not sure if that has any effect in any of these calculations.

Rick
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Old 06-14-2019, 05:19 PM
  #29  
RickDett
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I'm not giving up on points yet but the pertronix is beginning to look very good.

I don't have old junkyard can coil so my next step based on the information from Peterbuilt’s specifications from a 1974 Corvette I did a road trip first to Napa and tested an ECH IC12 coil that from my understanding is supposed to be a robust coil. Not happy with those numbers so I continued on below is what I found.

Napa ECH IC12, 1.5 ohms, 9.26 Secondary
Pepboys Accel 4180, 1.6 ohms, 9.50 Secondary
Pepboys UC12T, 1.6 ohms, 8.39 Secondary
Advanced Auto 26189 Driveworks, 1.8 ohms, 11.81 Secondary
Advanced Auto 26189 Carquest 1.7 ohms, 10.15 Secondary
Advanced Auto Accel 4180, 1.6 ohms, 9.46 Secondary
Advanced Auto E30 BWD E30, 1.4 ohms, 8.82 Secondary
Advanced Auto A/C Delco U505 (GM 12337166) 1.7 ohms, 10.01 Secondary
Auto Zone Valuecraft C818VC, 1.3 ohms, 9.20 Secondary
Auto Zone Duralast C819, 1.6 ohms, 11.89 Secondary
Napa (Another) ECH IC12, 1.5 ohms, 9.21 Secondary
Napa ECH IC12SB, 1.5 ohms, 8.24 Secondary

Based on the numbers Driveworks. Or A/C Delco because of the quality??

Thoughts on which one?

Rick

Last edited by RickDett; 06-17-2019 at 10:12 AM.
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Old 06-16-2019, 03:42 PM
  #30  
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I had a problem with quickly failing points on an off-topic ride. Turns out every new condenser I had gotten was completely junk. Almost fake.



Some interesting reading on the state of today's aftermarket distributor parts: http://nonlintec.com/sprite/cap_failure/

I set up an old chrysler points distributor hooked up to a power drill, resister and coil. This allowed me to spin it on the bench and see what the points where doing. With the "new" condenser there was a massive arch at the points. Hooked and unhooking the condenser made no difference. I robbed an old condenser off a parts dist and it almost eliminated all the arching. I ordered the large white caps mentioned in the above link and tested them on my rig. They do about the same job as the good vintage condenser so when the time comes I will have to find a way to mount one externally since they will not fit under the cap where the stock one fit.
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Old 06-16-2019, 08:24 PM
  #31  
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Just bought a new condenser from a good local parts store and it was also total junk. Just for discussion, you can check whether a condenser is any good with your ohmmeter. To start, touch the terminal on the lead to its case; this will discharge the cap. Now connect your ohmmeter positive lead to the terminal on the lead; then touch the negative lead to the case while watching the ohmmeter needle. The ohmmeter should immediately read 0 ohms (short), then rise in resistance to max reading. Now, reverse the leads (negative lead to the terminal, then touch the positive lead to the case). Again, the ohmmeter should immediately read 0 ohms, then rise to max reading. This indicates that there is no resistance as the capacitor is fully discharged, but that it will charge quickly...whenever the probes are reversed.

The condenser I got at the parts store did NOTHING....no matter how I checked it. DEAD! (Made in China)
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Old 06-17-2019, 06:44 AM
  #32  
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When you take a coil inductor and charge it up and then open the circuit, the stored energy has to go somewhere when the field collapses (opening the points). I am not sure but think the capacitors job might be to take the brunt of the energy and safely discharge it rather than burn up the points. Is the capacitor circuit open somehow...not a good connection on the can. If it is supposed to be grounded check to see with your ohm meter.

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Old 06-17-2019, 03:49 PM
  #33  
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A capacitor in a circuit is either an energy 'reservoir' (if it is not defective) or it is a non-entity (if it is not defective). Is it possible that a capacitor can present a 'short' to the system? I suppose that anything is possible...but I've not seen a shorted capacitor. Usually, they just have ZERO ability to store energy.
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Old 06-17-2019, 04:31 PM
  #34  
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Originally Posted by 7T1vette View Post
A capacitor in a circuit is either an energy 'reservoir' (if it is not defective) or it is a non-entity (if it is not defective). Is it possible that a capacitor can present a 'short' to the system? I suppose that anything is possible...but I've not seen a shorted capacitor. Usually, they just have ZERO ability to store energy.
The capacitor (condenser) is in parallel across the points. Capacitors conduct DC until fully charged. When the points open the current flows through the capacitor for a split second until fully charged then it acts as an "open" breaking the circuit and allowing the field to collapse in the coil. . The capacitor completing the circuit momentarily allows the points some time to open up a good enough gap to prevent arcing over.

https://en.wikipedia.org/wiki/Snubber

With out the capacitor its arc city.

Last edited by ConnecticutJunkman; 06-17-2019 at 04:33 PM.
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