MTFCA Forum

So, I have had a Strobospark tester for years and always considered it to be something on the order of a gold standard. Recently I rebuilt two Wilson HCCT's and had the meters rebuilt. At about the same time I was able to purchase a Weston bench meter and so now I have four meters to adjust coils with. Problem is that two of the four read about the same amperage when testing the same coil but the other two are off and the Strobospark seems to be the worst of the bunch. 1.3 amps on the two that agree only test about .9 amps on the Strobospark. Whether I can recalibrate is not so much a problem as which is correct. Is it possible to build a "test" coil with solid state guts which can be used as an absolute 1.3 amp "gold standard" to establish a firm target for adjusting with the other meters? High voltage output would not be necessary but current at varying voltage would be. I have tried to order an ECCT but they are not available right now. Maybe having five test devices will only make the issue more confusing.

a man with a watch always knows the time
a man with two watches is never sure

an ECCT tests for, and adjusts a coil by an entirely different philosophy than traditional methods. You cannot compare a coil adjusted with it to ANY other method.

My advice on getting your coils to test equally on 4 different setups, none of which have been calibrated to the same standard is this: Relax

So long as you have 4 coils adjusted equally by SOME method, you are good to go.

Which method is best, is an entirely different subject beyond the scope of your question and not what you asked.

David; Regarding comparing the meters, you can connect the ammeters in series to a coil and compare the readings, each one is measuring the same current, calibration as you suggest, requires a known load or a known, properly calibrated ammeter in series with ones you are calibrating. I suspect the Strobospark excitation current will read low b/c the Strobospark current turns off briefly between spark pulses and measuring that current directly with an AC current meter includes a significant portion of '0' current added to the pulse that fires the coil. Does the Strobospark current value show ~1.3 Amperes when you read 0.9 on the Weston? If it does, that would imply to me that the current is turned of roughly 1/3 of the time.

I agree with Scott, adding more meters, devices, etc achieves little additional value. And if you use HCCT, Strobospark, etc to adjust all coils to the same value with no double sparking they will work well. I have never had a properly rebuilt coil set up carefully on my Strobospark fail ANY of the tests on an ecct, including the ttf test. YMMV, respectfully, jb

To partially address the question: there are several types of meter movements and each one behaves differently. I asked this same question several years ago....why are my meters giving different readings. Some knowlegeable person on this forum explained that the difference is in the meter movements. I compared the readings to the readings from friends HCCT to establish which meter to use.

A rough way to set a coil which will start the engine. The points and the capacitor must be good. As always, I recommend testing the capacitor. Testers are very affordable
1. Set the cushion gap at about .005 in.
2. Set the bridge gap at .025 in.
3. Connect fresh 2 D cell batteries in series to the coil then
adjust the tension at the point that the coil will barely buzz.
4. At this point the current will be around 1 3 Amp and the coil spark should jump a 1/8 inch gap. If it doesn't, increase the tension.

Check which meter is close to this reading. At this point the engine should start but maybe not great.

I agree that an ECCT is the best simple method available to set the coils. Oscilloscopes seem to be beyond the scope of the many of the posters on the forum.

Art Mirtes

All good advice and well received. I have a garage full of good running ModelT's and Fordson tractors that I have rebuilt the coils in over the decades and they all start and run well. Many have remarked about how easily they start so the question isn't one of desperation but of detail. I agree that movements and meters will all have their own personalities but the fact remains that an amp is an amp is an amp and it seems to me that there should be a rather small range of variance. I agree with Scott that a man with two clocks doesn't know what time it is but my office has a half dozen or so clocks, watches, computers, etc. and if any of them varies by more than a minute or so I make corrections. My curiosity is about whether there is a iron clad, bulletproof way to verify the value. I can compensate once I understand where the difference is.

I have tried to order an ECCT but they are not available right now.

Supply chain issues have impacted the availability of lots of items these days as many are well aware, the ECCT is no exception. The good news they should be available again in March as the 2022 Touring season ramps up again here in the US.

Oscilloscopes seem to be beyond the scope of the many of the posters on the forum.

Here is a comparison between a ECCT adjusted coil and HCCT adjusted coil as viewed on an Oscilloscope that may be of interest. For those not familiar with an oscilloscope, it measures and displays voltage (or current in our case) versus time on the X axis of a X,Y style chart. Coil current is displayed on the vertical Y axis and time is displayed on the horizontal X axis. Play the videos one at a time and observe the differing characteristics as each coil fires 100 sparks.

https://www.facebook.com/groups/Fordmod ... 238305548/

The desired coil performance goal to watch for is: 1. How long it takes the coil current to ramp up to the same peak value before dropping abruptly back to 0A (that is the instant spark fires) and 2. How consistently the coil repeats that same current ramp time to fire spark (i.e. drop to 0A). Referring to the top video: Coil current starts out at 0A, rises linearly in nearly straight line to a peak value of 6A then drops abruptly to 0A as spark fires. The more consistent all 4 coils repeat that same behavior, the more consistent ignition timing and the more smooth the engine will run. If the time it takes the coil current to drop abruptly jumps around as seen in the bottom video, ignition timing also jumps around and engine performance degrades.

the fact remains that an amp is an amp is an amp and it seems to me that there should be a rather small range of variance.

True, but how that current flow and the steadiness of the current flow is displayed can vary significantly depending upon the principal of operation and physical construction of the measuring device (aka Ammeter). Here are a couple of links that provide further insight:
https://en.wikipedia.org/wiki/Ammeter
https://uk.rs-online.com/web/generalDis ... ters-guide

In the case of the HCCT, an RMS responding Ammeter is used such as a Moving Iron type construction. These are typically easy to identify by the non linear scale at the lower end of the scale. The accuracy, calibration and damping of the displayed AC current indication on the needle of an analog Ammeter all contribute to the variation one can expect to experience when different meters of the same physical construction are used to measure the same AC current. Also factor in the human factors of a person hand cranking the HCCT at differing rates of speed and consistency of that cranking speed (not to mention all the other variables of the coil point adjustment) and its no wonder why the interpretation of HCCT current readings is a frequent topic. Trying in vain to find that elusive "gold standard" measurement metric using the HCCT provided strong motivation to develop the ECCT.

I have a similar problem with tire gauges. A number of gauges will give varying readings on the same tire at the same time... but which one is right, or closest to right? I have to guess, since I have no known pressure source to test them against. I have a dial type USA made gauge that I depend on. Whether it's accurate or not, I do not know, but it's close enough. I don't know if the low priced digital readout gauges are any more accurate, but I doubt it.

Thanks Mike for the meter and oscilloscope explanations. I hope that those who severely criticized me in December 2021 for suggesting that there are other means of properly setting coil have read this. There are other means just not as easy to use as the HCCT.

I am about ready to suggest a way to reduce oil leakage through the rear axle bearings.

Art Mirtes