Bench testing a coil
Thread Starter
Burning Brakes
Joined: Mar 2006
Posts: 1,101
Likes: 171
From: Colorado Springs, CO
Bench testing a coil
Can anyone tell me the proper procedure and resistance readings for checking a coil? I recently saw an article in a vette mag, but now, of course, I can't find it.
Thanks in advance for any help.
Thanks in advance for any help.
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
I bought a new Standard Brands coil, and these are my test results,primary ckt,across positive and negative= 2.8 ohms.....secondary ckt,each side to tower=10,800 ohms. I'm sure there is a range on good coil numbers,but sorry,I only have these actual hard numbers on a good, new,replacement coil,I bought for my 65.
Race Director
Joined: Oct 2005
Posts: 12,468
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
Accepted values are 1.7 ohms primary, 8K-11K ohms secondary.
Slight variations are fine.
infinite ohms, or zero ohms is a problem.
Doug
Slight variations are fine.
infinite ohms, or zero ohms is a problem.
Doug
Safety Car
Joined: Mar 2001
Posts: 4,359
Likes: 116
From: AUSTIN Tx
Here is the determinative method for bench testing a coil.
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
Racer
Joined: Jul 2001
Posts: 486
Likes: 0
From: LONG ISLAND NY
Here is the determinative method for bench testing a coil.
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
Thats funny and it will wake you up
Pro
Joined: Oct 2005
Posts: 524
Likes: 22
From: St. Charles Mo.
Here is the determinative method for bench testing a coil.
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
That method will definitely test the coil. If you fly about two feet then your coil is producing about 35K volts and is pronounced good! If on the other hand you only bang your head on the hood of the car and that hurts more than the shock from the coil it is weak and needs to be replaced. 
Ever test an ignition condensor and the hand it to an unsuspecting bystander?
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Racer
Joined: Feb 2007
Posts: 309
Likes: 2
From: San Antonio Texas
Yes, it is in Corvette Fever magazine and I have the magazine and article at home. I went and bought a new multimeter, and after testing 3 brand new coils exactly the way the article said, all 3 coils failed. They were a brand new one from NAPA, made in USA, and a brand new flamethrower I and flamethrower II from Corvette Central.
The first test, came in correctly at 1.6 ohms with the multimeter dialed at 200. ( simply put red lead on positive terminal and negative lead on negative terminal).. Then I did like the article said, set the dial at 20k, and put red positive lead on positive terminal and the other negative lead in the hole where the coil wire inserts. This reading should have been over 13 ohms, and on all 3 brand new coils I could only get 9.5 to 10 readings, which the article said is a failing number..
I am having Dan Martin, my corvette guru, check this flamethrower II with his mulitmeter this week just to see if my brand new multimeter is faulty, or the article is faulty.. LOL
Cheers, Zale
The first test, came in correctly at 1.6 ohms with the multimeter dialed at 200. ( simply put red lead on positive terminal and negative lead on negative terminal).. Then I did like the article said, set the dial at 20k, and put red positive lead on positive terminal and the other negative lead in the hole where the coil wire inserts. This reading should have been over 13 ohms, and on all 3 brand new coils I could only get 9.5 to 10 readings, which the article said is a failing number..
I am having Dan Martin, my corvette guru, check this flamethrower II with his mulitmeter this week just to see if my brand new multimeter is faulty, or the article is faulty.. LOL
Cheers, Zale
Drifting
Joined: Oct 2008
Posts: 1,936
Likes: 92
From: Rochester Hills Michigan
Yes, it is in Corvette Fever magazine and I have the magazine and article at home. I went and bought a new multimeter, and after testing 3 brand new coils exactly the way the article said, all 3 coils failed. They were a brand new one from NAPA, made in USA, and a brand new flamethrower I and flamethrower II from Corvette Central.
The first test, came in correctly at 1.6 ohms with the multimeter dialed at 200. ( simply put red lead on positive terminal and negative lead on negative terminal).. Then I did like the article said, set the dial at 20k, and put red positive lead on positive terminal and the other negative lead in the hole where the coil wire inserts. This reading should have been over 13 ohms, and on all 3 brand new coils I could only get 9.5 to 10 readings, which the article said is a failing number..
I am having Dan Martin, my corvette guru, check this flamethrower II with his mulitmeter this week just to see if my brand new multimeter is faulty, or the article is faulty.. LOL
Cheers, Zale
The first test, came in correctly at 1.6 ohms with the multimeter dialed at 200. ( simply put red lead on positive terminal and negative lead on negative terminal).. Then I did like the article said, set the dial at 20k, and put red positive lead on positive terminal and the other negative lead in the hole where the coil wire inserts. This reading should have been over 13 ohms, and on all 3 brand new coils I could only get 9.5 to 10 readings, which the article said is a failing number..
I am having Dan Martin, my corvette guru, check this flamethrower II with his mulitmeter this week just to see if my brand new multimeter is faulty, or the article is faulty.. LOL
Cheers, Zale
I wondered if a coil from the 60s would check different. I checked my original 091 and got the same as you: 1.6 and 10K. Dunno
Bill
Thread Starter
Burning Brakes
Joined: Mar 2006
Posts: 1,101
Likes: 171
From: Colorado Springs, CO
Now I'm really confused! I found the article, and my coil reads 1.7 across the terminals and 6500 at the secondary.... Could this cause cutting out at high rpm? I also checked a new, unused coil (mexican variety) and it only read 8500 ohms at the secondary. 
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
Yes, it is in Corvette Fever magazine and I have the magazine and article at home. I went and bought a new multimeter, and after testing 3 brand new coils exactly the way the article said, all 3 coils failed. They were a brand new one from NAPA, made in USA, and a brand new flamethrower I and flamethrower II from Corvette Central.
The first test, came in correctly at 1.6 ohms with the multimeter dialed at 200. ( simply put red lead on positive terminal and negative lead on negative terminal).. Then I did like the article said, set the dial at 20k, and put red positive lead on positive terminal and the other negative lead in the hole where the coil wire inserts. This reading should have been over 13 ohms, and on all 3 brand new coils I could only get 9.5 to 10 readings, which the article said is a failing number..
I am having Dan Martin, my corvette guru, check this flamethrower II with his mulitmeter this week just to see if my brand new multimeter is faulty, or the article is faulty.. LOL
Cheers, Zale
The first test, came in correctly at 1.6 ohms with the multimeter dialed at 200. ( simply put red lead on positive terminal and negative lead on negative terminal).. Then I did like the article said, set the dial at 20k, and put red positive lead on positive terminal and the other negative lead in the hole where the coil wire inserts. This reading should have been over 13 ohms, and on all 3 brand new coils I could only get 9.5 to 10 readings, which the article said is a failing number..
I am having Dan Martin, my corvette guru, check this flamethrower II with his mulitmeter this week just to see if my brand new multimeter is faulty, or the article is faulty.. LOL
Cheers, Zale
Melting Slicks
Joined: Jul 2000
Posts: 2,097
Likes: 99
From: Boston MA
I also believe my 5 dollar Chinese made meter from Harbor Freight is wrong. It appears to read 1 ohm high. I get 2.8 ohms across the primary,instead of 1.7. When I measure across my ballast resistor I get 2.6 ohms,instead of the 1.8. I guess you get what you pay for.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,145
Army
Decent multi-meters usually have a 'zero' adjustment for the resistance function so you can calibrate it quickly. Some of the new Pertronix coils have 0.6 ohm and even 0.3 ohm resistance so don't get thrown if you have one of these....
Team Owner
Joined: Feb 2009
Posts: 21,315
Likes: 2,828
From: Nearby Mayberry in NC
Crowd Plow For Now
Here is the determinative method for bench testing a coil.
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
Hook the - terminal of the coil to the negative post on a 12 volt battery, then hook a wire from the positive post on the battery to the + terminal on the coil. When you remove the wire from the positive post, a spark should jump from the coil wire and knock you off your chair. If this occurs, the coil is good!
Regards, John McGraw
...reminds of the write up of the guy in Texas who tested the taser on himself.
Melting Slicks
Joined: Sep 2003
Posts: 3,050
Likes: 2
From: Orange Ct
The ohm meter will only check the coil at very low voltages. It will not show winding break down at operating voltages, fast rise time (as would be found in electronic ignition systems) or internal HV shorting to the case. All will cause problems that may not be apparent until the system is called upon to produce spark at higher rpm and cylinder pressures.
The ohm meter will not show the actual inductive reactance of the windings. Without a scope, pulse generator and other various test equipment, substitution is the only practical test.
The ohm meter will not show the actual inductive reactance of the windings. Without a scope, pulse generator and other various test equipment, substitution is the only practical test.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
The best way to check a coil is to hook the damn thing up and run it. You will find out pretty quick if its good or not. You can do all the bench testing you want, but if that thing breaks down under heat, you ain't going to know it until you put it under a little stress.
I have an original on my `33 Cadi. Works great for show, but after 30 minutes or so, she will quit dead. I run it only for show, and change it for go.
I have an original on my `33 Cadi. Works great for show, but after 30 minutes or so, she will quit dead. I run it only for show, and change it for go.
