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Old 03-01-2021, 09:18 PM   #1
fourfords
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Default testing coils & Condensers

Is there any effective way to bench test early V8 coils and condensers without expensive equipment?
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Old 03-02-2021, 03:13 AM   #2
Veeder
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Default Re: testing coils & Condensers

You can measure the resistance of the coil should be around .6 ohms. The condenser can be done with an ohmmeter as well but they are all slightly different. Place your meter on the R1 scale if you have a meter with different settings and if it starts with some resistance value and builds up to a short (within seconds) it is likely good. But they are so cheap when in question get a new one.

Caution - what ever you do don't use your meter on the coils if you have the hooked up to 6v or 12 v as there is a good chance you might destroy your meter
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Old 03-02-2021, 05:21 AM   #3
deuce lover
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Default Re: testing coils & Condensers

I use a multimeter to test for continuity on coils on the bench.If it buzzes its closed (good),no buzz -its open(no good).Now when on the car running and gets hot and circuit breaks then obviously coil is not good.I am unable to test for that.
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Old 03-02-2021, 08:40 AM   #4
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Default Re: testing coils & Condensers

You can test a coil with an multi-meter set to the "ohms" (resistance) scale. Please be aware that you will have to use two different settings for the primary and secondary windings. Use the 0-20 ohm scale to test the primary circuit resistance between the two small terminals on the coil. It should be in the low single digits (depending on coil type). Use the 0-20,000 scale to test the secondary circuit (between the coil wire terminal and ground. It should be in the 4 or 5 digit (5000-20000) range. Please note that these are only ballpark numbers depending on coil type. If you get a reading outside these ranges, you can be pretty sure the coil is bad.

It is possible to test a condenser for functionality with an analog meter, but it is not definitive. For this, you will need a special (read : expensive) multi-meter with a special capacitance scale. This will read out the capacitance of the condenser. Readings between .20 and .40 microfarads are acceptable.

As "deuce lover" alluded to, both condensers and coils can be affected by heat (and vibration). To fully test either component, they should be "heart-cycled" while being tested. This is generally impractical to do in the real world, and it is easier to simply replace the component and see if it solves the problem, given the relatively low cost of these components. With some of the unreliable sources common these days, multiple replacement might be necessary to isolate the actual problem,
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Old 03-02-2021, 02:45 PM   #5
rotorwrench
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Default Re: testing coils & Condensers

A person can set up a test rigg with any old distributor and enough test leads to connect stuff up. The grounding has to be common to the battery ground so the spark plug & distributor should be grounded to get a spark. A spark plug high tension wire connected to the coil's secondary tower with a good spark plug at the other end, will tell if the coil will work.

A person can use a slow turning drill motor to operate the distributor. With the breaker circuit & condenser all connected to form the operating circuit and the battery connected to the coil & plug ground, a person would be ready to test. If there is a lot of arcing at the points during testing with properly set points then I would suspect a bad condenser. If there is very little or no arcing and the plug has a good spark then it's at least functional. Leave the coil connected up for a minute with the points closed and warm up the coil for a test for open windings in the coil primary. It should still generate a good spark whether warm or cold and points should have little or no arcing.
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Old 03-02-2021, 05:53 PM   #6
tubman
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Default Re: testing coils & Condensers

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Quote:
Originally Posted by rotorwrench View Post
A person can set up a test rigg with any old distributor and enough test leads to connect stuff up. The grounding has to be common to the battery ground so the spark plug & distributor should be grounded to get a spark. A spark plug high tension wire connected to the coil's secondary tower with a good spark plug at the other end, will tell if the coil will work.

A person can use a slow turning drill motor to operate the distributor. With the breaker circuit & condenser all connected to form the operating circuit and the battery connected to the coil & plug ground, a person would be ready to test. If there is a lot of arcing at the points during testing with properly set points then I would suspect a bad condenser. If there is very little or no arcing and the plug has a good spark then it's at least functional. Leave the coil connected up for a minute with the points closed and warm up the coil for a test for open windings in the coil primary. It should still generate a good spark whether warm or cold and points should have little or no arcing.
Quite frankly, while this is good advice, it is really beyond what the average hobbyist wants to do. Swapping components is still probably the best way to to find out what is really going on.

Last edited by tubman; 03-03-2021 at 09:06 AM.
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Old 03-02-2021, 10:29 PM   #7
fourfords
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Default Re: testing coils & Condensers

Wow! Thank you guys! Success is on the horizon!
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Old 03-03-2021, 12:58 PM   #8
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Default Re: testing coils & Condensers

I’ll add that I believe the coil designed to work with a resistor should be about 1.0 ohm. Can type coil designed for no resistor should be about 1.5 ohm. (These designed to be powered at 6 volt which will allow 4 amps or less thru the points)

Also, not sure how accurate the typical meter can be at this extreme end of the scale. The meter’s own internal resistance, connectors, and probes can at a few tenths of an ohm. And the meter’s battery condition probably adds variability.
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Old 03-03-2021, 02:46 PM   #9
rotorwrench
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Default Re: testing coils & Condensers

Capacitor testers are available that will test for capacity, resistance, and leakage but they can be higher dollar than most folks want to pay. The all or nothing test with a multi-meter will only tell you that it will build a charge but that's about it. It won't tell you what the capacity is or whether it leaks the charge too fast. A person can use a 9-volt battery to build a charge and then check it with a volt meter to see if it is holding a charge for a minute or so. It will show close to 9-volts on the meter to start and then it will rapidly dissipate the charge through the meter but it will tell you if it leaks or not. A person needs a higher voltage to check some caps but this rudimentary test will tell a person something anyway. Just remember, DON'T TOUCH THE LEAD while holding the cap. It will bite you good. That's the hard way to see if it will hold a charge.
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Old 03-03-2021, 05:22 PM   #10
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Default Re: testing coils & Condensers

Both the coil and condenser Have to be about 225 degrees when testing
or the test is NO GOOD. G.M.
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