Capacitors and amperage draw

Discuss all things Model T related.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules

Topic author
Dennis_Brown
Posts: 213
Joined: Wed Jan 09, 2019 10:14 pm
First Name: Dennis
Last Name: Brown
* REQUIRED* Type and Year of Model Ts owned: 1926 Roadster pickup
Location: Spring Hill Fl
MTFCA Number: 21458

Capacitors and amperage draw

Post by Dennis_Brown » Wed Jul 06, 2022 2:04 pm

In testing a coil, if the capacitor is failing will it draw more amperage or less amperage or not be noticable?

User avatar

TRDxB2
Posts: 5455
Joined: Tue Jan 08, 2019 4:56 pm
First Name: Frank
Last Name: Brandi
* REQUIRED* Type and Year of Model Ts owned: Speedster (1919 w 1926)
Location: Moline IL
Board Member Since: 2018

Re: Capacitors and amperage draw

Post by TRDxB2 » Wed Jul 06, 2022 3:38 pm

http://www.mtfca.com/discus/messages/80 ... 1248132830
By Chris Barker July 19, 2009
I have found similar results. I think that you have to separate the two properties of the capacitor.
A good one should have capacitance (microfarads), but infinite resistance (ohms).
If you have zero capacitance, the coil will not work, whatever the resistance.
If you have some leakage - but the resistance is still very high - several megohms, it will work as long as it also has capacitance. There will come a point where the resistance is so low that it stops the capacitor charging up when the points close.
I don't know what values to put on these properties, but if it works on the HCCT I suggest use it - but carry a spare because someday it will fail.
I have also encountered coils with modern capacitors that have failed (no microfarads).
The past is a great place and I don't want to erase it or to regret it, but I don't want to be its prisoner either.
Mick Jagger


Art M
Posts: 850
Joined: Wed Jun 19, 2019 12:57 pm
First Name: Art
Last Name: Mirtes
* REQUIRED* Type and Year of Model Ts owned: 1923 Touring
Location: Huron, Ohio
MTFCA Number: 32489
MTFCI Number: 24068
Board Member Since: 2016

Re: Capacitors and amperage draw

Post by Art M » Wed Jul 06, 2022 9:58 pm

I highly recommend getting a capacitor test instrument. They are available on line and are easy to use.
Even if you choose to have the coils professionally rebuilt, you will know when to sent them in.

Art Mirtes


Been Here Before
Posts: 627
Joined: Mon Oct 07, 2019 2:00 pm
First Name: George John
Last Name: Drobnock
* REQUIRED* Type and Year of Model Ts owned: 1922 Coupe
Location: Central Pennsylvania

Re: Capacitors and amperage draw

Post by Been Here Before » Thu Jul 07, 2022 12:44 pm


Post Reply Previous topicNext topic