This would have been great for the 20th Frenzy
Thread Starter
Rennlist Member
Joined: Mar 2014
Posts: 917
Likes: 23
From: Gatineau, QC
This would have been great for the 20th Frenzy
I will test both of mine to see.
http://autorepair.about.com/od/troub...l-test-ohm.htm
http://autorepair.about.com/od/troub...l-test-ohm.htm
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Joined: Oct 2001
Posts: 20,506
Likes: 564
From: Bend, Oregon
Always a good idea to do this test if you suspect that your coil is giving you problems.
Things to think about as you test:
-- The coil wiring must be disconnected from the coil as you test resistance.
-- Meters read total resistance in the "loop" you are testing, including the resistance in the meter leads and their connections to the meter. Since we are testing for a fraction of an Ohm in the coil winding, you'll want to determine the meter lead resistance first by touching the two leads together. Then subtract this number from the total resistance number you see through the coil primary windings to determine the part of the reading that is those coil windings.
-- For the primary winding, use the smallest resistance range available on your meter.
-- Make sure the coil posts are clean and bright before you test. Even a small amount of crud or oxidation will give you a false high reading when you test the primary side.
-- If you replace coils, make sure you get the right ones. Parts-store universal replacement coils won't do.
--If one in a dual-coil system is suspect, replace both at the same time.
Mechanical damage is a common cause of coil failure. You might drop the coil and break part of the tower insulation where the high-tension lead connects. Vibration and heat are the other external causes of failure. Look for oil leaking out, swollen casings, and external arcing damage.
The oil leaking out is likely a PCB (Poly Chlorinated Biphenyl) transformer oil. PCB's are on the EPA **** list, known to be carcinogenic. Got a leak from the coil? Wear gloves and wash your hands immediately if you get any on them.
Using the wrong coil wire connector or insulator can lead to arcing in the tower connection. Inspect that end of the coil carefully for evidence of arcing. That might include what looks like min weld spatter or other discoloration. It's easy enough to clean the inside of the tower and connections with a brass gun brush. If you are replacing the coil(s) on S4+ cars, make sure your new coil is correct for the coil wire you have. Better wire sets include both styles of coil wire.
Damage to the windings is almost exclusively caused by internal arcing between the windings. Failing high-tension wires and poor spark-plugs and connectors are common causes of this. The ignition system in the later 928 includes the solid-state switch modules on the front apron, supporting a much higher voltage in the coil secondary windings. There are sticker warnings to avoid killing yourself by holding a live ignition wire. None there to remind you that leaving the coil secondary open during testing will damage the coils. If you try the old-school spark test of holding the coil wire away from a ground point as the engine is cranked over, you risk coil damage. There's more to this beyond coil damage, for a separate discussion.
Happy testing!
Things to think about as you test:
-- The coil wiring must be disconnected from the coil as you test resistance.
-- Meters read total resistance in the "loop" you are testing, including the resistance in the meter leads and their connections to the meter. Since we are testing for a fraction of an Ohm in the coil winding, you'll want to determine the meter lead resistance first by touching the two leads together. Then subtract this number from the total resistance number you see through the coil primary windings to determine the part of the reading that is those coil windings.
-- For the primary winding, use the smallest resistance range available on your meter.
-- Make sure the coil posts are clean and bright before you test. Even a small amount of crud or oxidation will give you a false high reading when you test the primary side.
-- If you replace coils, make sure you get the right ones. Parts-store universal replacement coils won't do.
--If one in a dual-coil system is suspect, replace both at the same time.
Mechanical damage is a common cause of coil failure. You might drop the coil and break part of the tower insulation where the high-tension lead connects. Vibration and heat are the other external causes of failure. Look for oil leaking out, swollen casings, and external arcing damage.
The oil leaking out is likely a PCB (Poly Chlorinated Biphenyl) transformer oil. PCB's are on the EPA **** list, known to be carcinogenic. Got a leak from the coil? Wear gloves and wash your hands immediately if you get any on them.
Using the wrong coil wire connector or insulator can lead to arcing in the tower connection. Inspect that end of the coil carefully for evidence of arcing. That might include what looks like min weld spatter or other discoloration. It's easy enough to clean the inside of the tower and connections with a brass gun brush. If you are replacing the coil(s) on S4+ cars, make sure your new coil is correct for the coil wire you have. Better wire sets include both styles of coil wire.
Damage to the windings is almost exclusively caused by internal arcing between the windings. Failing high-tension wires and poor spark-plugs and connectors are common causes of this. The ignition system in the later 928 includes the solid-state switch modules on the front apron, supporting a much higher voltage in the coil secondary windings. There are sticker warnings to avoid killing yourself by holding a live ignition wire. None there to remind you that leaving the coil secondary open during testing will damage the coils. If you try the old-school spark test of holding the coil wire away from a ground point as the engine is cranked over, you risk coil damage. There's more to this beyond coil damage, for a separate discussion.
Happy testing!
Rennlist Member
Joined: Apr 2006
Posts: 35,695
Likes: 511
I will test both of mine to see.
http://autorepair.about.com/od/troub...l-test-ohm.htm
http://autorepair.about.com/od/troub...l-test-ohm.htm
Thread Starter
Rennlist Member
Joined: Mar 2014
Posts: 917
Likes: 23
From: Gatineau, QC
Always a good idea to do this test if you suspect that your coil is giving you problems.
Things to think about as you test:
-- The coil wiring must be disconnected from the coil as you test resistance.
-- Meters read total resistance in the "loop" you are testing, including the resistance in the meter leads and their connections to the meter. Since we are testing for a fraction of an Ohm in the coil winding, you'll want to determine the meter lead resistance first by touching the two leads together. Then subtract this number from the total resistance number you see through the coil primary windings to determine the part of the reading that is those coil windings.
-- For the primary winding, use the smallest resistance range available on your meter.
-- Make sure the coil posts are clean and bright before you test. Even a small amount of crud or oxidation will give you a false high reading when you test the primary side.
-- If you replace coils, make sure you get the right ones. Parts-store universal replacement coils won't do.
--If one in a dual-coil system is suspect, replace both at the same time.
Mechanical damage is a common cause of coil failure. You might drop the coil and break part of the tower insulation where the high-tension lead connects. Vibration and heat are the other external causes of failure. Look for oil leaking out, swollen casings, and external arcing damage.
The oil leaking out is likely a PCB (Poly Chlorinated Biphenyl) transformer oil. PCB's are on the EPA **** list, known to be carcinogenic. Got a leak from the coil? Wear gloves and wash your hands immediately if you get any on them.
Using the wrong coil wire connector or insulator can lead to arcing in the tower connection. Inspect that end of the coil carefully for evidence of arcing. That might include what looks like min weld spatter or other discoloration. It's easy enough to clean the inside of the tower and connections with a brass gun brush. If you are replacing the coil(s) on S4+ cars, make sure your new coil is correct for the coil wire you have. Better wire sets include both styles of coil wire.
Damage to the windings is almost exclusively caused by internal arcing between the windings. Failing high-tension wires and poor spark-plugs and connectors are common causes of this. The ignition system in the later 928 includes the solid-state switch modules on the front apron, supporting a much higher voltage in the coil secondary windings. There are sticker warnings to avoid killing yourself by holding a live ignition wire. None there to remind you that leaving the coil secondary open during testing will damage the coils. If you try the old-school spark test of holding the coil wire away from a ground point as the engine is cranked over, you risk coil damage. There's more to this beyond coil damage, for a separate discussion.
Happy testing!
Things to think about as you test:
-- The coil wiring must be disconnected from the coil as you test resistance.
-- Meters read total resistance in the "loop" you are testing, including the resistance in the meter leads and their connections to the meter. Since we are testing for a fraction of an Ohm in the coil winding, you'll want to determine the meter lead resistance first by touching the two leads together. Then subtract this number from the total resistance number you see through the coil primary windings to determine the part of the reading that is those coil windings.
-- For the primary winding, use the smallest resistance range available on your meter.
-- Make sure the coil posts are clean and bright before you test. Even a small amount of crud or oxidation will give you a false high reading when you test the primary side.
-- If you replace coils, make sure you get the right ones. Parts-store universal replacement coils won't do.
--If one in a dual-coil system is suspect, replace both at the same time.
Mechanical damage is a common cause of coil failure. You might drop the coil and break part of the tower insulation where the high-tension lead connects. Vibration and heat are the other external causes of failure. Look for oil leaking out, swollen casings, and external arcing damage.
The oil leaking out is likely a PCB (Poly Chlorinated Biphenyl) transformer oil. PCB's are on the EPA **** list, known to be carcinogenic. Got a leak from the coil? Wear gloves and wash your hands immediately if you get any on them.
Using the wrong coil wire connector or insulator can lead to arcing in the tower connection. Inspect that end of the coil carefully for evidence of arcing. That might include what looks like min weld spatter or other discoloration. It's easy enough to clean the inside of the tower and connections with a brass gun brush. If you are replacing the coil(s) on S4+ cars, make sure your new coil is correct for the coil wire you have. Better wire sets include both styles of coil wire.
Damage to the windings is almost exclusively caused by internal arcing between the windings. Failing high-tension wires and poor spark-plugs and connectors are common causes of this. The ignition system in the later 928 includes the solid-state switch modules on the front apron, supporting a much higher voltage in the coil secondary windings. There are sticker warnings to avoid killing yourself by holding a live ignition wire. None there to remind you that leaving the coil secondary open during testing will damage the coils. If you try the old-school spark test of holding the coil wire away from a ground point as the engine is cranked over, you risk coil damage. There's more to this beyond coil damage, for a separate discussion.
Happy testing!
Thread Starter
Rennlist Member
Joined: Mar 2014
Posts: 917
Likes: 23
From: Gatineau, QC
Captain Obvious
Super User
Super User
Joined: Aug 2003
Posts: 22,846
Likes: 348
From: Cambridge, Ontario, Canada
