When I am trying to get the amps at 1.3 to 1.5 on the coils what voltage should I be using? The original car voltage is A.C. and could be as much as 28V so do the hand crank testers ( Which folks say is the best) put out A.C. or D.C. and what voltage? Thanks - Shane
The HCCTs put out A.C. voltage just like the car mag which, in fact, they are since they use the car flywheel, magnets and field coil. The voltage varies with speed just as in the car.
There are both A.C. and D.C. powered "buzz boxes" available which will allow you to adjust the point tension to the proper current draw. The great drawback of these units is that they work fine on a coil that is known to be good. By that I mean that the coil windings are in good condition, the internal capacitor has been replaced with the PROPER modern capacitor and the points have been set up and adjusted to move smoothly within the set parameters for same. The buzz box CANNOT diagnose a leaky or breking down cap, winding problems, etc. This can ONLY be done on a HCCT or John Regan's Strobospark unit.
I'll let John Regan or Ron Patterson explain the nitty-gritty details of the process. As someone explained in another thread, a proper set-up coil will start to spark at around 2 Volts.
I can't emphasize the importance of proper coil repair and adjustment enough. I've seen numerous occassions where a coil would spark in a buzz box and looked great (nice fat blue spark at the jump points) but as soon as it was put into its working environment (in the car) there was an obvious ignition problem. The buzz box was a cheap practical way back when these coils were fairly new and age had not taken a toll on them but today there is no guarantee on the results you'll get.
Voltage , being AC or DC , really doesn't matter in calibrating coils.
Ford coil units are amperage units.
Buzz boxes were never a practical way to properly set coils.
Condensers are checked with ohm meters not buzz boxes or HCCT.
This being said, I will defer to Ron or John for their say.
Six volt DC will work fine. I used to have a buzz box and as Warren states, if everything is in good condition you can get the car to run and run fairly well with it. However, set it on a machine that verifies the cushion spring is set to only allow single sparks and the engine will run even smoother.
To all newbies, the buzz box will work to get you going but you really should find a HCCT (or someone near you that has one) and calibrate them the way they left the factory.
As Warren points out the HCCT generates AC voltage just like the car and ranges from a low point (when the coil will operate) of 2 volts to over 7 volts. Because of engine speed the car magneto voltage is higher at 7 volts to over 30 volts in many cases.
It is important to remember that the Model T coil is a current device and, when properly adjusted, will operate at 1.3 amps on ac or dc voltage of a wide range.
The speed with which the coil gets to 1.3 amps (when the points open and the spark plug fires) is dependent on the rise time of the voltage.
As Warren points out, the magneto voltage output increases as engine speed increases and the coil will get to 1.3 amps faster as voltage increases. This is important because the cranksahft moves faster as speed increases and the coil must operate faster to maintain proper spark timing.
When operating on DC the coil has a fixed operate speed and cannot keep up with increased engine speed. This subject was explained in detail in the article in the following link.
More on Model T Spark Timing
Bob, Gary and Warren are correct that the Buzz Box tester is OK, but won't allow you to get the best performance of the Model T coil.
If you can find a HCCT or Strobospark tester,or at least get access to one, and buy the three Coil Rebuilding videos sold by the MTFCA you will have everything you need to rebuild your own coils.
If you run into trouble give shout we are always willing to help. Some of us are more into the technical details than others and can provide simple answers to coil problems, but we have no secrets and will share our knowledge freely.
Ron the Coilman
If you are trying to set your points without a hand crank coil tester or strobo spark you are wasting your time. Since you have not completed a profile we do not know who you are or where you live. I have a hand crank coil tester and would be happy to help you if you are nearby, check my profile and contact me off line. By the way, that offer is good to anyone who is in the vicinity.
Well I was too slow typing before Ron posted so much of mine is repeat but here it is.
The one major draw back with a buzz box is it can't tell you if you are getting a double spark which only an HCCT or John's unit can show. A double spark is the result of an improper cushion spring setting that causes a premature spark followed by a second one as the magnets continue to pass the mag coils. Both of these sparks are weaker then one that occurs at the peak of the AC sign wave.
I learned this after adjusting several coils using a buzz box and having the amp setting dialed in at 1.3 amps, however, when tested on a HHCT almost all were producing a double spark requiring me to go back and clean and adjust the cushion springs to eliminate the problem.
With the new reproduction points being made it is important to get hold of one of Ron Patterson's cushion spring pliers that he is having made up to properly make this adjustment since these new have had a problem with this setting.
In these time relay shots you can see a typical double spark resulting from a non fuctioning cushion spring. The pointer can't be seen since was moving to fast too register.
Here's the way it should look once the cushion spring has been set properly. If I had repositioned the flywheel these sparks will occur at each of the 16 segment on the brass ring. Bob