Re: Condenser woes

P D /
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A quality condenser should last a very long time .

Here are a couple quotes I borrowed , to answer your question :


Re: what makes a good condenser go bad? #9

B-racer Jeff Schlemmer

Shakopee, MN, USA USA

1950 Willys Jeep Pickup "Ratrod"

1971 MG MGB

2014 Dodge Charger

Oct 23, 2013 07:32 AM

Top Contributor

Joined 11 years ago

16,688 Posts

You want to see .18-.22mF in a condenser, AND a proper bleed-down rate, generally full bleed-down in roughly 5 minutes. If either of those specs is out of tolerance, the condenser will not function properly.

Most condenser failures are caused by poor grounding, which does not allow a condenser to bleed down properly. It holds part of its charge instead of fully discharging, therefor overheating. Worn breaker plate assemblies are a HUGE factor, with moderate to poor to nonexistent grounds. Using 40+ year old engine ground straps is yet another problem. Engine grounding is a game of volume, like a garden hose. If you pump voltage into your ignition, coolant temp and oil pressure sensors, etc... you need an equal flow of electrons out that ground strap. Internal corrosion (not visible) is a HUGE problem and everyone ignores it...


And :


Re: what makes a good condenser go bad? #10

george stringe

Frederick, USA USA

1960 MG MGA 1600

Oct 23, 2013 09:41 AM

Joined 5 years ago

29 Posts

The capacitor (condenser) has two functions: 1) it absorbs the back EMF from the magnetic field in the coil to minimize point contact burning and maximize point life; and 2) it forms a resonant circuit with the ignition coil transferring further energy to the secondary side until the energy is exhausted.

When the points open and the magnetic field collapses it also induces a current in the primary as well. It's not very much because there are only a few windings in the primary, but it's enough to jump a small air-gap, such as the one between the just-opening points in the distributor. That tiny spark is enough to erode metal away from the points and you'll 'burn' the points. It prevents the points from arcing and prevents coil insulation breakdown by limiting the rate of voltage rise at the points.

You are unlikely to do anything to cause a condenser failure. A condenser is made by taking two long aluminum foil ribbons and putting an insulator in between them and rolling it up and putting it in a can. One foil is hooked to the can and the other is connected to the wire coming out. The failure is typically either a mechanical failure of the connections inside the condenser or an electrical failure of the insulating material separating the two foils.

Sometimes they do not use an insulating paper or plastic material between the two foils, but use a layer of aluminum oxide coating on the foils. The oxide coating is a nonconductor and is much thinner than any paper or plastic insulator but it can electrically fail or punch through and short the foils when high voltage charge is applied to the two foils in the condenser.

Keeping a known good spare is a good policy.


Both those quotes from :,2501990

This single post is part of a larger thread. Start from the top or view this post in context.
Subject Written By Posted
  Condenser woesTopic by: viv v viv v 04/02/18 06:03PM
  Re: Condenser woesRe: P D P D 04/02/18 07:06PM
  Re: Condenser woesRe: Probably Fred Probably Fred 04/02/18 08:50PM
  Re: Condenser woesRe: Don Ohio Don Ohio 04/02/18 08:53PM
  Re: Condenser woesRe: P D P D 04/02/18 09:13PM

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