Model T Buzz Coil

Could someone tell me how to check a Model T Coil before I go to all the trouble of soildering some clips on the post. Thanks -- Benny

The way I do it is to just hook a 6 or 9 volt battery to the positive and negative terminals of the coil and see if I can make it buzz. Nothing fancy, but it works for me.

Mike, Does it hurt to run one with a 12 volt battery without putting a resitor in line?

The top and bottom post are primary, + and -, doesn't make any difference which way. The center button is secondary, be sure you have a wire with a 1/4 to 3/8" gap for the spark to jump. Letting it buzz wqithout a place for the secondary to go is asking for trouble, it will find a path inside the coil and burn the insulation. 12 volts won't hurt it, just don't leave it buzzing, when running it only see's momentary contact.

[Paul Spence]

Benny: I use a ohm meter and measure the resistance between the contacts +, - and zzapppp (spark). Top(+) to bottom(-) should almost be a short, and top(+) or bottom(-) to the center(zzapppp) should read a higher resistance around 33K ohms. If you get an open then you need to work on it. Usually just cleaning the points and all the connections on the top of the coil does it. Then you may need to adjust the tension on the botton set of points by bending them at the coil connections just a bit up or down to get the proper BUZZZZZ. Really need a meter to measure the current draw which should be around 1.5 amps. More than that has a tendancy to burn the points and shorten battery life. Then if the condenser is bad......... . Operating the coil without a spark plug or tester connected can short out the secondary, then it's junk. 6-12 volts doesn't hurt mine. To much to cover all at once. Paul

Benny if it doesnt buzz try cleaning the points and tighten all the nuts that hold the points not the one thats adjusts the points.BobRR

Sorry if I implied letting the coil sit there and buzz. A quick touch of the wires to the terminals is enough. It may not be right, but I managed not to cook my coils using this "quick and dirty" method. Careful with that secondary terminal, I can testify to how much it steps up a 6 volt battery!!

The secondary resistance should be 3-4000 ohms NOT 33K ohms. The other thing which is very important is the bridge contact on the armature which moves. When the armature is pulled in, the contact is on a spring which lets it travel 5 mils or so before breaking the contact with stationary point. This lets the field build up which collapses when contact broken giving a hot spark. Many times a coil will be considered weak when in fact, this bridge spring on the armature is not working. Also replace the condenser. I have rebuilt 60-80 of these things and I replace over half of em. Any old automovive condenser will work with 0.2 microfarads at 600 volts. NEVER run them without a spark load !!




my new web site URL

Gentlemen,

The T coils were designed for 6 volts. The buzz box takes that 6 volts and steps it up to maybe around 10,000 volts for the spark plug. If you run it on 12 volts, you will double the output voltage. The coils may break down and short or arc, the original condensor (if it still has it) may break down under double the voltage. I'm sure there are folks out there running these on 12V but I wouldn't - they weren't meant for it.

Norm

Wiring Diagram if needed.




Kevin's Old Iron

Norm:

I don't think that 12V will hurt a "T" buzz coil as long as there is a spark plug gap of .050 or less in the secondary circuit.

Model T engines had an internal low-tension AC magneto that, at speed would put out around 30V. Doing the calculations gives an equivalent to approximately 20V DC.

I agree that the condenser might go south at 12V on a coil that has been used a lot or has been sitting around for a long time but it probably would croak on 6V after a while anyway.

Take care - Elden

The first thing to do is determine if it actually is a T coil. 6 volts will make a T coil spark but performance will be poor unless you adjust the coil to draw extra current. If you have ever tried to run a T with a bad mag on 6 volts you will find this out. If I forget to change my electric start T to mag it will act sluggish when I try to wind it up and when I change to mag it will take right off... Most guys that have T's with bad mags use 12 volts and get decent performance. I have seen a good T mag put out about 40 volts at 1600 rpm and the coils last just fine.




My Old Engine and T page

Thats AC Volts But I run my T-coils on 12 volts as they do work much gooder bedder. LOL

Havin a blast preservin the past

Randy L Peterson

Thanks to all that replied, it sure has helped a old man a lot. I also learned a lot by HARRY'S Ignition page.I have five coils that will be at my house next week and would just like to test them before building a buzz coil box.Thanks again and thanks HARRY for this site, if it was not for you I would not be in this expensive hobby. Benny


http://www.old-engine.com/magneto.htm

Hi Benny:

I am a Model T restorer. I have three of the contrary things and I have rebuilt dozens of coils. I have a coil tester that will check the amps and the spark intensity. I can replace the capacitors (if that is the problem) and points with new ones if needed. Let me know if I can help.

Larry

Hello Kevin: I saw your diagram on the wiring and I had to go look at my 25 Roadster. On a car the battery wire goes to the contact on the very bottom of the coil and the timer goes on the very top contact. Do you wire them different for the hit and miss application? I have a friend wanting me to give him a coil for his IHC engine, do I need to tell him to wire it diffently????????? Thanks

Benny take it to the shows that you attend Im beginning to see alot T Model coil checkers at shows. saw one in boonvile Ind last week. sold mine to a friend six months ago. A lot of people do not know what they look like. It is a hand cranked magneto with gagues. designed to check mag coils horn sparkplug. early ford dealers had them in their shop.

Either one is fine so long as he wires a timer to break the circuit. The T uses a positive ground, right? I think that's the only difference between your description and Kevin's drawing which shows a negative ground.

Nope, the T uses a negative ground. Buzz coils don't care as they were built to work on AC anyhow.... It is a good plan to reverse polarity once in a while as it will even out point deposits...

I have one of those buzz coils but know nothing about them cept from these threads. I would venture to say this one is probably quite typical as it's in a wood box with "FORD" on the front side. Some of the Re's make mention of the "top side" the terminal(s) on the bottom side, left side, right side... I would like also to test this one and can do so by following the suggestions in this thread. Where the problem is, I don't know what "top", "bottom", "right side", "left side" is. The measurements of this box are ( measuring with it standing on end, contact points on top, "Ford" printing facing me ) 5" tall, 3-1/4" in width & 2" thick. (depth) There are two contact points (solder connections) on the left side and one on the bottom side when sitting in said position. Am I correct in assuming that one of the two solder points on the left side is for + or - from battery and the other for the timer and is the lone connection on the bottom for the spark plug? Is the condensor on the inside of the wood box or is/was that mounted remote? If in the wood box, how does one go about getting the box open without cracking or destroying it?