I have a JD 1020. I installed , points, condensor, cap, rotor, coil and wires. I even installed a new ignition switch. I either get intermiten spark (very weak) or no spark. Not sure what I am doing wrong. It has a prestolite distruber 12 volt system.

I guess you could have the ignition analyzed on an oscilloscope. Maybe a tech could see something then.
I always heard the only gap was the spark plug gap-the rotor has no gap-are you sure you got the correct rotor? And does it touch the top distributor cap coil wire tower?

Let us know. It is a mystery worthy of a solution.

It could be, but anybody with a multimeter could quickly test it, give you a good idea if it is good or not. Just take the two wires off-the wire going to the distributor would be the negative side, and the wire from ignition switch is the positive side. There should be a + sign, and a - sign on each side of the coil case where the wires connect. Then remove the coil to distributor high tension cable, remove the coil from it's bracket and take it to a friend or shop to have tested. All they would do is measure the resistance of the coil at two places, using an ohmmeter (part of a multimeter), to see if it is within specs. A shop charge should be like $5, if they would even bother to charge you.
What else might it be? Well, one could check if power is passing from the switch to the coil on that wire. The wire on the coil should show battery voltage, or very close, when key is turned to on. Also examine your plug wires for brittleness or cracking. If no spark at any plug, it could be a bad coil to distributor high tension lead-the one from coil tower to center of distributor cap.
Also pertinent to note that the mechanical points and condensor assembly inside the distributor has to be working right for spark to occur. This is what the small wire from coil to distributor connects to- the points. Someone knowledgeable about how it works would need to look at it-the points have two small electrical plates or contacts that open and close as the distributor shaft turns around. This opening and closing is what makes the coil able to generate the high voltage for spark to occur at the plugs. Higher voltage travels from the coil tower to the top of distributor, and on to the individual spark plug wires, routed to each in turn in the firing order by a simple device called a rotor.
Take off the distributor cap, and right on the top of the distributor shaft is the rotor. It has to be in good working order to transfer current from the coil high tension wire to the individual spark plug wires.
Post back. Keep me informed of your progress. You must have the old 6 volt system? Amazing! Buy new plugs, plug wires, points and condensor for it. And a coil, if you need to-good luck. Parts may be hard to find. First check locally, may need to go online for a vintage parts supplier.

do you have a bad wire or a bad wire going from the points to the coil

HEI distributor and burning coils,it in you connection first make sure you install primary and secondary prorperly as it comes out of the cap , and inside the cap wire from modules dont make contact if you are burning its from primary circuit, this is the (B+) or (battery most likely), your secondary is your tach and that need to switch from postitive to negative for it to create spark obvously if tach was grounded or applied power you wont start,but there are times the condensor in the distributor does stays fixed and shorts out the coil (replace that condensor its for suppression) when the condensor is replaced run a fused direct wire at B+ (from ignition) run the vehicle and monitor the tach wire and check to see if that get hot

You might check ground. some of these units were ground positive. did you switch the posts?This would cause problems since the electrons are on the inside of the condinser.
Good luck
Joe

The ignition module in the distributor is what you need to give the engine spark to the plugs. It senses signals from the PCM to regulate the spark control and this item is the part that took over the old style point & condensor type ignitions. It is time for a new one in your truck

Is it cranking? Is there a spark? If there is no spark. I would look at the points again; unless you mean you replaced them now instead of in the fall. Look at the points and if they look frosted then try sanding them or replace them again. They can go bad quickly if there is moisture in the cap. Recheck the gap. It is possible that you got a bad condensor if the points are good. Check the cap and rotor for corrosion and remove this coorosion or replace them. Check that you have voltage at the coil. It might be a bad ignition switch. If all this is good turn the crank till the points close, turn the key on and check for a spark with the coil wire within a 1/4" of a ground when you open the points with a screwdriver. If it has spark; try spraying a little starting fluid into the carb. Let us know what you find out.

check the gaps on plugs also distributor also condensor in distributor

Check for power getting to the center top connection at the coil.
Are the points opening?
Are they fully closing?
Check for a grounded connection/wire in the dist?
Be very careful how you set the coil onto the dist.

Hello, I see you have changed all but the condensor? this may be the last item to sort it?
Have you tried a hot wire direct to the coil to eliminate ignition switch?
Hope this helps!
Please remember to rate my effort.
Paul 'W'
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