Condensers

Vern

Vern

Well-known member
Is there a way to test condensers? I got these recently, but don't know if they're any good. Thanks for the insight.
 

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My Fluke 87 DMM has a setting to to test the value (microfarads) of a condensor, but doesn't tell if they are good or not.
 
They are not going to be reliable. Do not use them unless you like replacing them on the road.

From experience. Back 40 years ago I was testing all sorts of 'new' old condensers for the A. They would always fail eventually.

The best tester is the coil condenser tester. They will warm it up and show a fail state quickly.

Do NOT even think for a moment the capacity tester (size of the condenser) on a meter is going to tell you if the unit is dead. It is rare a bad condenser shows the wrong value. They fail because the separator has 'dried' out or changed its chemical properties. This changes their resistance (in simple terms) in use and allows leakage.

Your best best is a quality burn out proof condenser.
 
Patrick L. said:
Probably every one of those is better than the cheap new chinezium ones of today.
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Actually, NO.

But a lot of made in china caps are not well made. You would want made in Japan caps.

So the condensors will go bad with time. The 'paper' between the foil is treated with a chemical that will go bad with time. They go bad real fast with some heat.

The made in China caps have poor quality control. You can read about Mustang guys putting new name brand condensors in their cars only to fail quickly. The caps are sourced low bid and the companies do not care about quality since they make up a small part of their business.

FWIW, I am constantly having to deal with failed caps as part of my job. So I am up on the problems that are out there. In fact I have a failed made in china 2 year old cap on my desk as I type this. Came out of a computer power supply that was supposed to be a high quality. That one cost $50. I will have to buy $200 power supplies that are made of very high quality capacitors for those systems. These are regular desktop power supplies for normal computers.
 
did you know that most condensers that get replaced were not the cause of an ignition problem. just easy to go buy one and try it i guess.

yes you can test them using your DVOM as shown in the previous post in this thread. or do an online search. it is an easy test.

or here capacitor condenser same test
https://www.youtube.com/watch?v=FDuN7QHn1-s



i would even test the new one if i buy one.

ou
 
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Generally a condenser is either good or bad. An ohm meter will check whether it has gone open or not. The actual capacity is harder to check as most don't have the equipment, but, the points will tell whether its correct or not depending on which side of the points the build-up is on.
Its seldom when a good quality one fails.
 
I would only use them as spares and if all the new ones you have in inventory are gone from the shelf. They make work initially but fail as they get hot. You can get an idea of how the capacitor may be working electrically by taking an ohm meter and going across the capacitor. When you first connect the ohm meter to the capacitor, the capacitor is discharged and you should see on the meter a rapid increase in the meter reading. A discharged capacitor is like a dead short. As the capacitor reaches a charge, the resistance goes up, the current flow decreases and you should see the ohm meter reading slowing decreasing. A fully charged capacitor will not pass much current and the ohm meter will return toward zero. If the ohm meter does not behave the way I described it, the capacitor is defective. Ed
 
A fully charged condenser won't pass much current ?

Just grab ahold of a charged one. Mechanics used to think that was one of the great jokes to play on new guys.
 
A person can barely trust a modern cap made with Mylar film in this day and age due to construction processes. An old wax paper cap was good until the paper deteriorated which didn't take long with enough heat applied.

If a person doesn't have a real cap tester then just install it in the distributor and test it that way. I'd be surprised if any of those old ones like that would still function and even if they do, it likely wouldn't function for very long.

Keep them for historical value but don't expect then to work very long if at all.
 
Over the years I’ve had a good bit of trouble with condensers so I built Tom Wesenbergs coil tester and added the condensers and spark plug test as well.
 

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If they test OK, use them. Maybe you'll find a good one, but that's probably not the way to bet.

But an ohmeter or digital "cap checker" can't test them properly, as mentioned. Not completely or thoroughly. They need to be tested at high voltage, about 500 volts DC, to check for leakage current. Also required to test while the condenser itself is at normal operating temperature (HOT). Ignition service is rough duty.
 
In my 60 years experience with Model A's i have had one condensor go bad. It was new manufactured but I do not know the particulars. All of the original Ford build condensors did not fail.
 
nkaminar said:
In my 60 years experience with Model A's i have had one condensor go bad. It was new manufactured ...
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Right, but that was up to 60 years ago. Condensers fail over time, just sitting on the shelf, and the new manufacture .. well too often they are junk from the start. Provided the OEM condenser passes all the tests today that is best but most people don't have the test equipment. I have a half dozen or so of the "modern" 12 volt ignition condensers from the 1960s and sadly none of them will pass leakage tests at rated voltage. I suspect they will "work" but the ignition or spark output might not be what it should.
 
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