how do you test a coil to see if it is worth putting in capacitors and new points?
Here is a good thread on your question:
You can do some ohm readings to get an idea but the real proof is to test it with good points either with or without a new capacitor. Internal high voltage checks are are hard to test for and may not show up right away. You can install a condenser and test the coil before potting and closing up the box.
Found with a google search of this site for coil rebuilding.
Measure the high voltage winding resistance across the two terminals that are on the long side of the coil. You should read about 3300 Ohms.
If that is good then replace the points and condenser.
Dang fast typers
Capacitors there's no question in my book.
Replace them. Points can on occasion be re-used. Depends on the contact condition & cushion spring mostly. I've re-used decent point sets often. Usually I'll try to get a coil to work before any "surgery" but if it works it's only a candidate for a new cap. I use a toy train transformers AC accessory terminals to check them.
I was going to put a coil in my suitcase to take to Chickasha, and then I thought, no, those airport goons would go crazy, and probably think I was going to try to blow up the plane, so the coil is staying home, and I'll have to pay $12 to ship it!
Larry, I would take an old, unrestored coil. Let the airport goons do all the digging to get the tar out. Then it will be ready for new capacitors.
Larry, Good move. A few years ago we were driving a T from Canada back into the US. The border patrols noticed a couple spare coils I had in the back seat, and became interested very fast and none to friendly. I explained what they were and even took the top of the coil box off so they could see what they actually were. They finally decided a couple driving along in a Model T was not a threat to national security, and let us through.