coil question [Archive] - Chevelle Tech

: coil question

Jul 8th, 06, 11:41 PM
I had posted yesterday about this in chevelle tech but havent gotten a full answer so i will post here.
I am hooking my coil up and wanted to make sure the wires are going back in the correct places. Does the small condenser ,next to the coil, wire up to the positive? Does the red and yellow harness wire connect to the negative along with the aftermarket green tach wire?

Jul 9th, 06, 12:20 AM
Year, make, model, type of distributor?

On a points type distributor the yellow wire goes from the starter's "R" terminal to the coil's + terminal.
Should also be a whitish cloth like covered wire on the coil's + terminal
Red wire = ?
Tach connects to the coil's - terminal.
If I remember correctly, the condenser also connects to the coil's + terminal.

Jul 9th, 06, 7:31 PM
Its a stock points distributer on a 72. Theres a yellow/red wire that has a single connector on it. Wasnt sure if its - or +

Jul 9th, 06, 9:12 PM
The only thing on the - side of the coil is the trigger wire from the points and the tach wire.
I still don't remember the condenser wire :o

steve 72
Jul 9th, 06, 11:17 PM
That little codenser you are talking about is just for radio interference its screwed on with one of the coil bracket nuts

Jul 10th, 06, 12:30 AM really confused now. I just dont want to connect everything wrong.Is the trigger wire from the points a double red/yellow wire? This red/yellow wire is connected to - or +? The little cylinder condenser(radio interference?) is actually connected to the coil bracket and the wire and connector is only long enough to connect to the - or + of the coil.

Jul 10th, 06, 1:41 AM
Just leave the condenser disconnected for now although I doubt it would really matter which side of the coil it gets connected to.
I belive the trigger wire from the points is black but anyway you can see it's the wire coming out of the distributor.

I don't see any red/yellow wire on the diagram.

Jul 10th, 06, 7:51 PM
i traced the double red/yellow wire and it seems to go to the starter so i imagine this hooks up to the +side of the coil?

Jul 10th, 06, 11:35 PM
Must be the yellow bypass wire I was talking about then.

Jul 11th, 06, 3:22 AM
There is a single wire coming out of the side of your distributor housing. Connect that wire to the negative side of the coil. The double wire goes to the positive side of the coil.

The double wire is comprised of two wires. One is from the outer terminal on the starter solenoid, and gives the + coil full battery voltage when your ignition key is in the "Start" position. The other wire piggybacked on the same terminal lug is the "ballast resistor wire" and it is energized when the ignition key is in the "run" position. Its function is to supply the + coil with 8/9ish volts at all times while the engine is running. Basically the resistor wire is a carbon core wire of a known resistance value. Much like your present day spark plug wires.

The breaker points will burn up quickly if they are run at 12 volts. The reason being that at 12 volts there is a pretty powerful spark at the point that the points open. Hence the "Ballast Resistor Wire" to step voltage down to an acceptable value.

Even with the "Ballast Resistor Wire" there is still a spark when the points open and absorbing that spark is the job of the "condenser" which is attached to the breaker plate inside your distributor. If you ever lose spark and everything looks perfect then you probably have a bad condenser. Those things have fooled many a mechanic.

When they fail they usually fail to ground and all of your ignition current is permanently grounded until you replace the pesky thing. They prevent that field collapse that gives you your powerful secondary spark voltage.

The telltale symptom of a bad condenser is when you put a test light on the negative side of the coil and crank your engine. If you get a steady light that means the current flow is NOT being interrupted any more by the breaker points opening and closing , rather its going straight to ground through the faulty condenser.

What Dean and others are calling a "trigger" wire (Black) is actually a ground wire which completes the electrical circuit from the ignition switch through the PRIMARY side of the coil to the breaker points. When the points are closed you are saturating the primary winding in your coil with electromagnetic flux.

At the instant that the breaker points open the flux lines collapse across the SECONDARY windings in the coil and induce the high voltage , low amperage current that fires across your spark plug gap.

The "Condenser" you refer to on the outside of the coil is wired to the negative side of the coil. Its there for RFI (Radio Frequency Interference)suppression.

If anyone is interested in seeing all of this stuff about coils feel free to acquire an old coil at the local junk yard and take it apart. Interesting stuff to be found inside. Did you know that they are full of oil? Yuppers. Helps em stay cool. Of course I am referring to stock GM type coils.

Sorry...didn't mean to rattle on but you know how I get late at night. Is the moon full?

Jul 11th, 06, 12:48 PM
Thanks Charbilly. Now i can rest easy knowing im going to wire this thing right. One thing i was concerned about was how do i know the difference between a "condenser" and an "rfi"? I put on all new parts but im afraid the parts guy might have given me a condenser instead of an rfi. I compared it to the condenser in the distributer and it looks the samebut is longer and has a blue wire but has the same end as a condenser.

Jul 11th, 06, 7:40 PM
blaster, Forget RFI..that stands for "Radio Frequency Interference" . Its what your ignition system makes while its doing its job. You only know about it when you hear it as static on your radio.

GM's fix for RFI is to fasten a "noise suppressor" to the negative side of the coil. The term "noise suppressor" is basically synonymous with "condenser".

The "noise suppressor" captures the electrical impulses emanating from your coil that your radio sees as static such that you don't hear them coming out of your speaker(s). These impulses occur as induced current from the constant building and collapsing of electro magnetic fields acting upon the wiring of the ignition circuit.

The noise supressor is filled with a coil of paper onto which a conductive substance is afixed. That coil of paper is designed to "bleed" those electrical impulses to ground over time without interrupting the ignition current.

If you want to see this RFI at its extreme take a look at the older Corvettes with their metal shielded spark plug wires. Those Fiberglass bodies were rotten at shielding RFI from the radios in those cars.