So I have 5 coils from my grand-pa's 1917 T. It hasnt ran in about 40 years and as far as my mom can remember the reason it stopped running was an ignition problem.
How do I test if these coils are good to replace the capacitor? Ive read to check the ohms. But between which points, what should the reading be?
I have on order a batch of capacitors from funprojects.com for the rebuild.
Hi Scott - You need to check for resistance between the two contacts on the side of the coil. You should read about 3200+or- ohms. It does not have to be exact. Some of the later replacement KW coils will read around 2300 ohms.
John at fun projects makes everything you need to check out and repair your coils. Contact him and he will be glad to explain their purposes and use. There will be no disappointments with his products. We have used them for years with great results.
Scott I would also buy new points if you are going to replace the capacitors. The points will need to be properly adjusted on a hand cranked coil tester or a strobo-spark to 1.3amps with the cushion spring adjusted to produce a single spark.
Thanks everyone, got it all tested now.
So Ive tested all 5 coils and they are all around 3k ohms.
3 of the coils come out good on all the tests I found on coildoctor. The other 2 fail from the top side point to the farthest top points. Which should be a direct connection. Can this be repaired without to much work?
Where should I get the new point sets from? Once Im done getting them testing good on my multi-meter Ill be rejoining my local club and they have a hand crank adjuster. (Its been 2 years since I started work on the T and funds were slow...it needed alot of work).
Also Ive opened them up to start removing the pitch but it is soft on most of them. Any hints at getting it out?
Scott just be careful that you do not damage the secondary windings when removing tar. Here is a good drawing of the coil to show you how it is wired. Most of the time I find the wires that are connected to the bolts that hold the points have been twisted and the connection is broken. It is easy to re solder to make a repair.
Im just curious...can I just put the whole coil in the oven at a low tempature then fish out the whole condenser? or will that not work out well...
Think of the opposite approach. Put the coils in the freezer a day or two and it makes the tar brittle and easier to chip out. You still need to be careful of the windings. Works for us. Others may have different ideas.
Scott I agree with Erik, it takes some patience to get the tar out. I generally start with a straight slot screw driver and remove the tar from just above the glass insulator, there is a wire that runs from the bottom contact through the capacitor, many times if you can find the wire and gently pry the wire up the length of the capacitor it will crack the tar from above the capacitor making it easier to remove. I also dig out as much tar as possible from the bottom side of the capacitor, this will allow you to gently pry up on the bottom of the capacitor. It is ok if the wire is pulled away from the capacitor because you are tossing the cap and keeping the wire. Like I said it does take some time and patience. Removing the tar is the most time consuming part of rebuilding a coil. Like most things the more you do the easier it gets. Be gentle and take your time.
The new high dV/dT capacitors are "flatter" while the older "orange drop" shaped ones were round and much fatter. The bottom line is that you now do NOT need to remove the glass insulator for most coils and this is a much safer way to go since when removing the glass to make room for the larger cap, it was easy to stab the coil winding with your tool and that is fatal to the winding. Stay way to the left side of the coil as you face the sliding door side and dig the tar away from that side and work toward the glass divider but I doubt you will have to remove the glass. Sometimes the glass is in fact a wooden divider.
I really like your chart idea but you have the capacitor "OPEN" and capacitor "SHORTED" ohmmeter readings interchanged. When the capacitor is shorted the resistance with points held open will be ZERO while with the capacitor open the resistance with the points held open will be infinite. Please correct that and repost your chart. I like that chart idea a lot.
Some further thoughts based on my own experience:
Primary just rarely is shorted or open but CAN be shorted to the core so you might want to scrape off the tar and dirt from the top surface of the core using a razor blade scraper and then connect your ohm meter to the bottom coil contact and to the core metal wire bundle with ohm meter on the highest scale. Should measure infinity. When there is low resistance or shorted you can get all sorts of weird things like missing sparks at the spark ring on the HCCT and random snorts and belching when running the car.
Forget the oven for melting out tar. I in fact do use an oven to remove the tar to extract the windings but the tar will not evacuate the box cavity very well if you don't also remove the non terminal side as well as the sliding door and the none removable panel that is on the opposite side from sliding door. With 3 sides of the box removed the box is for sure then damaged. I don't care because I have selected only the worst box coils for melting out. Without removing those 3 sides you will only get enough tar out to fill up all the sliding door tracks and make it nearly impossible to get that thing back into place. Tar will be everywhere on you and if you heat up too much you can damage the winding. I have a very careful controlled procedure for doing this but the box is totally expendable when I do it. No other way around that. Heat needs to be kept high enough to melt the tar and have it flow but low enough to not damage anything. With that set of constraints you can't get the tar out unless you wreck the box sides as per my description. It is also very easy to pull the high voltage leads out of the winding by accident. My advise is to stay miles away from the winding at all times since you really don't need to get your tool near it now that the capacitor is flatter and needs a smaller cavity to fit into.
Thanks for the info, I have my coils in the freezer now.
I ordered the newer high high dV/dT capacitors since I figured putting something smaller into the box would be easier.
With the one I started with to practice is a junker... the wood is cracked and the readings are out of whack for all but the secondary windings. Figure Ill practice first then do it right once I know where Im poking around. On this one its a wood divider, found it right away and am only working on the safe side of it. Hopefully in a couple of days Ill have these dug out when the new capacitors arrive.
Im going really slow using a butter knife for my digging.
I like your chart, it pulls a lot of information into one place.
Other the the condenser ohm readings, another possible clarification may be the points settings. Here is what Ron Patterson said about setting the points, "We have also found that by increasing the .005 cushion spring travel to .010-.012 the coil works better and you can still properly install the points. It is not important which number you choose (.005-.012) but it is important that each of the four coils cushion springs are set the same to avoid inter cylinder timing differences.
One last point. Many people think the .030 point contact gap is the critical adjustment, it is not. As long as the contact gap is greater then the cushion spring travel the coil will operate correctly. This of course assumes that the cushion spring travel is the same on each coil AND the cushion spring has sufficient downward tension to properly "follow" the vibrator blade." From:
If someone did not know better and tried to set the points exactly as in your chart, they would likely not be ably to properly set the coils. The 1/32" setting may be a good approximate starting point but the final setting is what ever works.
Well my 1st coil turned into a total mess, cant find the wire on the bottom of the condenser... there is a piece of wood on both sides...
I opened up another (that had the original Ford stamp on the side) and it was totally different inside. Had the glass insularor. A block of wood between that and the primary/secondary. The condensor came out with very little work. Im guessing my g-pa previously repaired the 1st one...his electrical type repairs were interesting to say the least (oddly funny since he was an electrical engineer and designed power plants).
The condensor of the 1st coil is a totally different material. Much newer looking then the one I just removed. It was also round vs the oblong one I just removed.
Scott here is a photo of the capacitors that John was talking about. The "orange drop" is on the left and the newer thinner on the right. As you can see all you have to do is remove the old capacitor to fit the new style into the coil. The old style you had to remove the glass and re-arrange the wood blocks in order to fit the capacitor.
The freezer works wonders they coils are only taking about 15mins now to take out the old condensor.
Ive come across this odd coil though, the primary popping out of the top is totally different and the screws as well. Also the box is closed up with a staple. Should I junk this one or is it usable?
One of the others the box slpit down the middle on the side with the contacts upto to thop across the primary... then through the left side to the last bolt when looking at the coil side contacts on.... Im trying to do this rebuild as low cost as possible so would prefer not to buy new coils...
Also there is the bit of pride I did it myself
Between the 2 side posts its 2955 ohmns.
John Regan - Thanks for the correction - I had few experts proof read it and we all missed that mistake.
Jim Thode - I added a comment that all four coils should have the same cushion spring gap.
Here is a PDF version (better for printing it out):
Hi : Is there a max temperature of the tar to pour in . Can we damage the cap. when the tar is to hot ? The temperature of the tar what I use is about 300 degrees F.
What you have is probably a later aftermarket coil. They can be rebuilt, but finding the condenser is a little more work. Some are really small and hidden at the top left near the point mounting screws.
Scott, that coil in your photo was an after market with a .23 yfd capacitor that was designed to work on 12 volts DC. My advice would be to throw it away. I will not mention who first suggested it to me, but he has rebuilt a lot of coils.
I bought some of those new and the the strips were loose and would attach to the coil point and pull out of the box.
I also tried melting the tar with a heat gun and the wood caught fire before the tar got soft. That tar melts at close to 500 degrees.
Actually the first coils had Type 1 tar, then Henry went to Type 2 and had to go to Type 3 for the 1926 coils to keep the engine heat from melting out the tar. The difference is that about 100 degrees of higher heat is required to melt the Type 3 tar.
The next question is where to get more tar, which isn't easy to answer. Actually the only tar offered in Maryland was a 100 pound cylinder for about $100.
Now I leave coil rebuilding to the experts.
My coil rebuilding is as difficult as sending those babies to the Coil Doctor. =) I have a great multi-meter and no shortage of experience working with small electrical parts, but I don't have a way to test the points. So, it was way easier to focus on the rest of the car and leave the VooDoo stuff to the Witch Doctor, I mean Coil Doctor.
Scott - rebuilding coils is only part of the job - adjusting them correctly is more than 50% of the what is needed.
There are a number of people that rebuild and adjust the coils in the parts section of the MTFCA front page.
Ron Patterson, the Coilman, did a great job on my coils.
One less thing to worry about!
FWIW, I've found that the wires connected to the points mounting bolts are sometimes reversed from what's shown on the drawings. IIRC these were on KW coils, not Ford coils.
When checking coils w/a MM it makes a difference.
You'r right I have good luck with Ron Patterson Coils and also with RV Anderson does a lot of my coils
Scott, as I said it gets easier as you go. I don't like the reproduction coils with the flat bar primary. I would not use it. There are too many good rebuild-able original coils around. Here is an example of one Saturday's work. All new capacitors, re-potted with tar, new points and adjusted ready to go into service.
Scott, there are near countless postings throughout the years on coil rebuilding. Do a keyword search or just scroll thru the various years postings. Our wise teacher, Ron Patterson, seems to be absent on the forum as of late so those old messages are good reading. I went thru all of the forum messages for past years and saved everything related to coil rebuilding into MS Word documents for each year. It sure makes for an easy reference for me, but the more rebuilding I do - the less I need to reference them.
Yes you might get away with just taking some simple ohmmeter readings to determine the condition of the secondary coil but there are other tests that should be done to try and rule out (as best possible) the coils that aren't worth rebuilding.
My best advice for you - stick to rebuilding original Ford coils and if you're serious about learning the ins and outs of rebuilding, then buy the MTFCA Coil Rebuilding series of DVD's that are for sale from the various dealers and you will be then taught by Ron Patterson.
Here is a link to find the previous years Forums:
Regards (and more importantly, have fun),