Testing HEI coil
Thread Starter
Burning Brakes
Joined: Dec 2002
Posts: 1,069
Likes: 2
From: Sherwood Park AB
Testing HEI coil
How do you test an HEI coil?
I have read to test the coil by attaching one probe of an ohmeter to the rotor button on the dist cap and one probe to the tach, then batt wire from the coil. If both readings are infinite, the coil is no good. My new MSD tests "No Good".
I called MSD because the new coil I bought tests no good this way and they told me to test it with one lead to the rotor button, and one to the ground wire from the coil. If the reading is 9 ohms on the 20K scale it is a good coil. My new MSD tests Good.
What's going on?
I have read to test the coil by attaching one probe of an ohmeter to the rotor button on the dist cap and one probe to the tach, then batt wire from the coil. If both readings are infinite, the coil is no good. My new MSD tests "No Good".
I called MSD because the new coil I bought tests no good this way and they told me to test it with one lead to the rotor button, and one to the ground wire from the coil. If the reading is 9 ohms on the 20K scale it is a good coil. My new MSD tests Good.
What's going on?
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Originally Posted by rexx78
How do you test an HEI coil?
I have read to test the coil by attaching one probe of an ohmeter to the rotor button on the dist cap and one probe to the tach, then batt wire from the coil. If both readings are infinite, the coil is no good. My new MSD tests "No Good".
I called MSD because the new coil I bought tests no good this way and they told me to test it with one lead to the rotor button, and one to the ground wire from the coil. If the reading is 9 ohms on the 20K scale it is a good coil. My new MSD tests Good.
What's going on?
I have read to test the coil by attaching one probe of an ohmeter to the rotor button on the dist cap and one probe to the tach, then batt wire from the coil. If both readings are infinite, the coil is no good. My new MSD tests "No Good".
I called MSD because the new coil I bought tests no good this way and they told me to test it with one lead to the rotor button, and one to the ground wire from the coil. If the reading is 9 ohms on the 20K scale it is a good coil. My new MSD tests Good.
What's going on?
Also, sometimes a coil will check good at room temp ... but check bad at underhood temps ... and vice versa.
Last edited by jackson; May 24, 2006 at 01:23 PM.
