Crispy points.. Why?

Dave in Boise

Dave in Boise

Senior Member
Hi All,

I think my points might be worn out due to bad high speed performance (has new condensor, coil, cap and rotor). The question I have , though, is whether what I am seeing on the points is normal.. They wore down to .014 or so, so I cleaned them up and re-gapped. When cleaning up I found some white 'ash' on the points.. I used a points file gently, and then regapped to .020.. Ran better for a while but when re-examining the gap was back down, white ash again and the copper end seemed to be a touch blue. The cam is a new, b style dist cam and has just a touch of cam lube on it. The upper plate is a modern spring type. I have cleaned up the contact foot and lower spring plate..

Any ideas why? I never leave the key on, and always turn everything off with the master switch when stopping as well. What could be causing the points to wear and get white ash on them? Bad ground? Reversed polarity coil? This is a 12 v converted system.

Always, any help is appreciated..

Dave in Boise
 
what kind of coil. do you have a ballast resistor?
If the gap is getting smaller something must be causing rubbing block wear ---or the adjustment is moving. --there have been several posts about the spring contact lower plate system causing problems also --is that what you have??

I have always had better luck with old parts, except the A&L condenser, I bought that new ---but i guess that is old now at 25 years, I made my own lower plate wire from wire I salvaged out of a 60s chevy dist, it is the wire with many strands that can flex and not break

I have seen the white crust corrosion mostly on points that have sat for long times, a lot of the new production points i have seen lately are of low quality, it seems like they forgot how to make them.

If you can post good closeup pic of your points you will get better answers

Are the actual contact surfaces sort of blue and spotted??--with the white around the edges??
 
With the engine off, key on and points closed, how many amps does the coil draw?

A stock 6 volt system should draw about 4 amps, and drops to 1 to 1 1/2 amps with the engine running.

Do the points have good spring tension? Any sign of oil or grease contamination?
 
Kurt..
Coil is a brand new 12 v with internal ballast (came with the 12 v conversion kit)

Yes I do have a spring type modern upper plate.. I may drill both plates and run another wire to ensure good ground
(Are the actual contact surfaces sort of blue and spotted??--with the white around the edges?? ) Yes :)

Hi Tom, would the Amps fo r the 12v be about 1/2 of the 6v values? If so I believe I am in that ballpark looking at my amp meter

How do I tell if my coil is wired in the right polarity for a 12 v ssytem?

- Dave
 
Ther was a bit of an oily film, that I cleaned off with denatured alcohol when I first reset them.. There seems to be quite a bit of spring pressure, at least as good if not better than my other car I am comparing against
 
Dave in Boise said:
Kurt..
Coil is a brand new 12 v with internal ballast (came with the 12 v conversion kit)

Yes I do have a spring type modern upper plate.. I may drill both plates and run another wire to ensure good ground
(Are the actual contact surfaces sort of blue and spotted??--with the white around the edges?? ) Yes :)

Hi Tom, would the Amps fo r the 12v be about 1/2 of the 6v values? If so I believe I am in that ballpark looking at my amp meter

How do I tell if my coil is wired in the right polarity for a 12 v ssytem?

- Dave
Click to expand...

A short excellent read all about coil polarity here:
http://www.chicagolandmgclub.com/techtips/general/574.html
 
It kinda sounds like the points are getting hot.. Points don't like and won't last long on 12v volts so have you checked the voltage at them?? With an internal resistor coil they will start out at 12v but should quickly drop to 5-7v.. Coil polarity should be the same as the battery..
 
Dave in Boise said:
Kurt..
Coil is a brand new 12 v with internal ballast (came with the 12 v conversion kit)

Yes I do have a spring type modern upper plate.. I may drill both plates and run another wire to ensure good ground
(Are the actual contact surfaces sort of blue and spotted??--with the white around the edges?? ) Yes :)

Hi Tom, would the Amps fo r the 12v be about 1/2 of the 6v values? If so I believe I am in that ballpark looking at my amp meter

How do I tell if my coil is wired in the right polarity for a 12 v ssytem?

- Dave
Click to expand...

The coil on 12 volts should show about the same amps as the stock 6 volt system I listed.

If you aren't using a ballast resistor, the amps on 12 volts will be twice what I posted for the 6 volt system.
 
Voltage certainly kills points.. Try running them on 12v for awhile,, they'll only last a little while..Thats why the points voltage should only be appr 6v on a 12v system.. I've had to change a lot of them over the past 50 years for that reason..
 
12 volts WILL appear on one side of the points when they are open. its impossible for it to not too as its an open circuit, there will be no drop across the resistor or coil. When they are closed you will read zero because they are grounded, this is why Tom is using current measurements.

Voltage to an extent is meaningless to the points, only current has an effect. I wouldn't exceed 250V with the small gap though, they might start arcing across :)

The condenser / capacitor is parallel to the points to absorb the arc from the coil to some extent. A bad capacitor can easily burn points fast.




BTW. its only an assumption at this point but the day our A overheated and blew steam out of a lose hose, we ended up with white crust on the points, we assume from the steam.
 
Patrick L. said:
Voltage certainly kills points.. Try running them on 12v for awhile,, they'll only last a little while..Thats why the points voltage should only be appr 6v on a 12v system.. I've had to change a lot of them over the past 50 years for that reason..
Click to expand...

Myth one: Voltage kills points.
Voltage has nothing to do with killing points. Amperage is the culprit. If you go from 6V to 12V with the same coil, you double the amperage. Do you remember any of the basic electrical formulas? Amps squared X resistance = watts. In the case of the points, the watts provide the heat energy to burn away the contact material. The resistance is the internal arc resistance as the points 'break'. The voltage across the coil resistance determines the amperage through the points, from E=IxR.

Myth two: A resistor will limit voltage.
A resistor only limits current (amperage). Again, E=IxR. With E (voltage) as a constant at the battery, I (amperage) approaches zero as R (resistance, ohms) approaches infinity. If you put two devices, each one ohm, in series with a 6V battery, the voltage to ground measured before, between, and after each device will be 6V. A resistor sold as a 'voltage drop' is in reality a way of limiting amperage.

Myth three: 6V & 12V coils, internally ballasted coils.
Coils are designed to have a certain primary/secondary winding turns ratio. The applied voltage determines the current (amps) through the primary. Changing the gauge of the primary wire changes the amp draw. A "12v" coil uses thinner wire, not an internal resistor. "ballast" is a misnomer in this case.
 
I'm not going to argue with anyone, even though I love a good agrument.. I do know and remember ohms law.. I don't care.. If its voltage or amperage that kills points, I don't care, its semantics to me.. In the days of points ignition not many folks carried ammeters around with them,but, everyone had a test light.. 12v across a 12v bulb = bright lite.. 6v across a 12v bulb= dim lite..Thats what you looked for/at..If 12v didn't/doesn't hurt points then all the manufacturers spent a lot of time and money needlessly installing resistors to cut the primary voltage[ cuz thats what they wanted you to check for]to the distributor.. An under or over capacity condensor/capacitor will cause pitting/cratering, but, the points will still last awhile.. OK, I'm done, you won't hear anymore about this subject from me.. If we still disagree, thats OK..
 
Patrick L. said:
I'm not going to argue with anyone, even though I love a good agrument.. I do know and remember ohms law.. I don't care.. If its voltage or amperage that kills points, I don't care, its semantics to me.. In the days of points ignition not many folks carried ammeters around with them,but, everyone had a test light.. 12v across a 12v bulb = bright lite.. 6v across a 12v bulb= dim lite..Thats what you looked for/at..If 12v didn't/doesn't hurt points then all the manufacturers spent a lot of time and money needlessly installing resistors to cut the primary voltage[ cuz thats what they wanted you to check for]to the distributor.. An under or over capacity condensor/capacitor will cause pitting/cratering, but, the points will still last awhile.. OK, I'm done, you won't hear anymore about this subject from me.. If we still disagree, thats OK..
Click to expand...

A light bulb = a load on the resistor = a voltage drop across the resistor.
I'm not a mechanic, but I am an electronic technician, and i'll admit it i've never used a test light :).
 
In China and Mexico they don't care if a condenser works or not, they just slap it together as they are told. If it's crap then the end user is the only one who got jyped. If the condenser works well, the points last better. I've run a 3 Ohm primary coil without a ballast for several years in my old 64 T-bird with the same points and condenser. I changed it when the transistors went bad in the old ignition module. So far so good but it too will die someday.
 
You must log in or register to reply here.
Back
Top