points diagnosis

Long ago when I was in tech school (mid 70's) and there were still a lot of points vehicles out there they taught us a diagnosis method about which side the damaged contact was and shape of damage (i.e. cone on fixed side means check XXXX, cone on moving side means check XXX etc.). I cannot remember this, and have a need of it now. Does anyone remember it?

heard a week ago or so, good way to clean up points is use a brand-new sparkly-new $100 dollar bill, and slide it through the closed points. The new bill has a nice sharp file/sandpaper touch to it. I know, a hundred, but ....

I would be outa luck most days-LOL-----

If the mound is on the positive side it calls for a higher capacity condensor. If the mound is on the ground side of the points it calls for a less capacity condensor. I didn't remember this I had to get out my auto electric book.

I've heard that explanation, guess it makes sense... But what do you do about it? I've never see the mfd's listed on an automotive cap.

I can just imagine asking the Auto Zone tech that question! LOL

Or use the $100 bill to turn it into electronic ignition!

dr sportster has it right. In fact he explained it better than I could.

This condition is also caused by somewhat normal driving [ in a car]. Low speed city driving will transfer material to one side or the other. Points and condensors are sold almost together so playing with different capacities to change metal transfer would kinda seem like overthinking it to me.

they would want to know if its 4wd or not

Steve, you have made a mistake. The statement "Auto Zone tech" is an oxymoron. This is a creature that simply does not exist or is so incredibly rare as to be considered extinct.

Don't get me wrong here.....I purchase the majority of my parts and supplies from Auto Zone. They do serve an important function in the industry. However, the average employee is simply many times far removed from being a "tech" in any sense of the word.

Now, who would you ask a technical question about your car?
A) A $10/hr parts clerk?

B) A $30/hr mechanic?

And, whose advice/information would you consider more reliable?

I thought about getting electronic ignition, but then found that it would be pointless.

But seriously, folks, how do you go about getting a higher (or lower) capacitance condenser?

(quoted from post at 12:32:24 03/10/15) I thought about getting electronic ignition, but then found that it would be pointless.

But seriously, folks, how do you go about getting a higher (or lower) capacitance condenser?

Click to expand...

bucket full, a tester, start measuring & selecting.

Yup that is in My Chiltons from the mid 50s. If I remember most are like .7mfd. You can buy them up and down from that value. What it does is the cap. holds onto or dumps the potential voltage slower or quicker, thus the little cone build up if it is a little off. Another part of that is if you have the coil hooked up backwards! Not so much something other than what the book calls for but more if you drive mostly high speed and or heavy pulling can make a difference too. Jeffcat

Here's the deal as I understand it but remember I graduated EE school almost 50 years agooooooooo

When the points are closed and the coil is conducting current there's obviously no current through the shorted out condenser, its a big discharged empty electron bank sittin there. Then when the points open and voltage rises across the points and condenser, the condenser is initially at Time T = 0 +, like a short circuit and conducts current for a short time until its charged up after which it no longer conducts and appears as an open circuit to DC. Then when the points close again that stored condenser energy dissipates and its discharged. If the condenser is sized properly and the LC circuit is correctly sized current is near the same each time so points wear is equal on both sides. If its not the same due to an incorrect condenser value, you get a pit on one side and a hill build up on the other.

The condenser saves the points from premature burning as it accepts current and acts as a shock absorber reducing the burning and arcing across the points. If its open or no condenser at all, she still fires but a weaker spark plus the points burn up too fast. If the condenser is too big she will never fire at all. If its sized correct you get a strong spark plus the points last longer.

Electrons have mass so their bumping into the points sides has an effect and if you figure they are negative charged particles you can figure which way the pit or hill builds up.

John T Long retired EE so no warrantly lol

The quality control is poor so most mag repair persons use a meter to test the new ones and use ones that measure correctly. Capacitors come in a huge variety of standard sizes and ratings, buy the size you need then hope for the best.

John T