Capacitor

[Ralph F]

I have a question about capacitors, I had some coils rebuilt in 2020 and I had thought it would be a good idea to check them on a strobo spark and have 3 of them that have capacitor that have failed according to the strobo spark. My question is why would I this happen with 4 year old rebuild coils. These coils were professional rebuilt and set up on an ECCT tester.
Fitz

[Moxie26]

Hello Ralph... Be sure to have a piece of paper between your coil points before putting in the tester, then check for capacitor rating.. . Your stroboSpark tester possibly could be defective. Would there be anyone in your group that has a ECCT ?..... The method of setting/ adjusting electrical output of ignition coils with the ECCT, when put on strobospark or HCCT, will give different results than the HCCT and strobospark testers. ECCT coil sets will give equal firing since their output will be equal and balanced.......... Another method is to use an analog meter to test your capacitor , again have piece of paper between coil points , then test

[Adam]

If the rebuilder didn’t use a suitable type of capacitor, it is very possible the capacitor has failed.

[Ron Patterson]

I agree with Adam.
This response assumes appropriate capacitor testing technique was used.
The problem described sounds alot like metalized Mylar capacitors were used in the coil rebuild.
Some coil rebuilders like them because they are easy to install, but they don't last long.
May be a classic case of using they wrong type capacitor.
Ron Patterson

[Art M]

Are the less reliable capacitors the ones that are slightly flattened. They were available from model t supply sources about 6 years ago, but they don't seem to be available any longer. With these, the glass insulator could stay in the coil.

I bought 12 and installed most of them in 2018. I check them every year with a capacitance meter. They haven't deteriorated yet, but maybe they will in the near future. On the other hand, maybe these aren't the one being discussed.

Can someone comment.

Art Mirtes

[Ralph F]

thanks for all the replies, it came down to following directions. I need to put a piece of paper between the contacts.
Again thanks
Fitz

[Moxie26]

Good morning Ralph..... Happy to be helpful on your testing procedures, plus save you the expense and time of replacing good capacitors.

[Chris Barker]

Yes.
With the ECCT you mustn't touch both sides of the points if you hold them open with your fingers.

[MKossor]

See the ECCT FAQ page for more information on testing ignition coil capacitors using the ECCT.

https://modeltecct.com/faqs

FAQ: "Does the capacitor have to be replaced if it tests POOR?"

[Moxie26]

Ralph... With respect to the holidays and family, and have time to get back to your Model. T. Coils, let us know the results of your testing.

[John Codman]

Someone said to use an Analog meter to test Capacitors. Why wouldn't a digital meter work just as well?

[Moxie26]

Good question John... In my experience, digital meters sometimes will not hold to a value without fluctuating.

[Ralph F]

Morning, I have had a chance to go back and recheck the capacitor on a strobo spark and following the instructions found that the capacitor were fine. The proper way to test the capacitor is by putting a piece of paper between upper and lower contact. I then adjusted all of them to draw 1.2 amps, with no double spark.
Again thanks for all of the suggestions and advice.
Have a wonderful Easter
Fitz

[Moxie26]

Ralph... Here are some pictures from my file showing results of proper ECCT coil results

[Moxie26]

Since the iPhone camera will not accurately photograph things due to camera position, I assure that the upper bridge is perfectly straight to the surface of the wood coil case and to start there is a 0.030" gap. Coil adjustment will change during testing.

[Moxie26]

Extra photos found in stash...

[Moxie26]

This is the correct capacitor that our major vendors have available. . .... Some have referred to this as the "orange drop" capacitor.

[JBog]

Mouser Electronics sells reliable high DvDt capacitors.

Part #598-225P47494YD3. Made by Cornell Dubilier - CDE 225P47494YD3

That’s where I ended up buying mine.

[BE_ZERO_BE]

Just FYI :
 
The capacitors sold by Langs and most T suppliers are a custom
made capacitor for the Model T coil.
They have an even higher dv/dt that the SBE 418 or 225 series capacitors.
The current price of the 225P47494YD3 at Mouser is $9.04.
The current price of the coil capacitor at Lang's is $3.95.
The Capacitor question comes up periodically on the forum.
The best capacitor and best price is for the one from the T suppliers.

[Moxie26]

The 418 series capacitors are the ones that I received from one of the major suppliers of Model T parts

[JBog]

The 418 series capacitors are the ones that I received from one of the major suppliers of Model T parts

The 418 is what they sell, They don't sell custom made caps.

[Moxie26]

They sell what is beneficial to coil needs and performance.