Coil 1115270 Test Specifications

[Erv M.]

I have a 350/300 1969 coupe.

After a slight tuneup I started the car and the ballast wire went to ground where it crosses the shield box around the distributor. Caught it quick and turned off the ignition.

Fixed that issue however since then the car runs very rough, loading up on fuel. Exhaust will burn your eyes in the garage when idling.

I want to test the coil first. Does any one have the specification for the primary and secondary tests?

[Paul O.]

Re: Coil 1115270 Test Specifications

Erv do you have a shop manual for the 69 if you do the resistance measurements should be listed in the Electrical section of the manual. For both the Primary and Secondary circuits. Paul 18046

[Jack H.]

Re: Coil 1115270 Test Specifications

The '71 Chassis Service Manual list three 'omnibus' specs for coils. One for 6-cyl, one for std 8-cyl, and a third for V8 with TI. It doesn't break down the various coils by specific Delco PN...

But, the spec listed for std V8 coils is 1.77-2.05 ohms, primary, and 3-20K ohms for the secondary at 75F. That's pretty 'loose' (especially on the secondary), but it should be enough to detect a completely FRIED coil.

Remember, testing coils by measuring/verifying primary/secondary winding resistance is a necessary but NOT a sufficient test. You're getting NO VISIBILITY on the integrity of the coil's magnetic core and its ability to couple primary to secondary.

To really know what you've got, the coil has to be exercised at rated voltage/current to verify its overall primary to secondary energy transfer characteristics. Coils that were low on cooling oil and suffered thermal damage (core lamination separation) but are otherwise intact will test 'good' with a simple examination of winding resistance but act 'funky' when it comes to actually emitting spark waveforms under dynamic load...

[Terry M.]

[Erv M.]

Re: Coil 1115270 Test Specifications

The secondary range of 3 - 20k is a wide range. Does a lower value indicate the coil is better, worse or meaningless?

The '71 Chassis Service Manual list three 'omnibus' specs for coils. One for 6-cyl, one for std 8-cyl, and a third for V8 with TI. It doesn't break down the various coils by specific Delco PN...

But, the spec listed for std V8 coils is 1.77-2.05 ohms, primary, and 3-20K ohms for the secondary at 75F. That's pretty 'loose' (especially on the secondary), but it should be enough to detect a completely FRIED coil.

Remember, testing coils by measuring/verifying primary/secondary winding resistance is a necessary but NOT a sufficient test. You're getting NO VISIBILITY on the integrity of the coil's magnetic core and its ability to couple primary to secondary.

To really know what you've got, the coil has to be exercised at rated voltage/current to verify its overall primary to secondary energy transfer characteristics. Coils that were low on cooling oil and suffered thermal damage (core lamination separation) but are otherwise intact will test 'good' with a simple examination of winding resistance but act 'funky' when it comes to actually emitting spark waveforms under dynamic load...

[Edward J.]

Re: Coil 1115270 Test Specifications

Erv, check the choke butterfly to make sure that its not stuck in the closed positon.

[Duke W.]

Re: Coil 1115270 Test Specifications

Are you saying that the pink wires on the common terminal to the coil + side shorted to ground?

That wouldn't affect the coil.

You need to give a more precise description of exactly what short circuit occurred and whether you cranked the engine with the starter when the short was present.

Duke

[Jack H.]

Re: Coil 1115270 Test Specifications

Once again, it's NOT the resistance. That's simply telling you a given winding has continuity and approximately how many winds are intact (IF you know the characteristics of the wire, gauge, it was originally wound with).

A better test is the specific inductance of the two windings. A typical coil for that era is going to measure something like 2-3 ohms on the primary with an inductance of, say, 7 mH. While the secondary will read somewhere in the 8-10K ohm area with an inductance of, say, 70 H.

It's the inductance ratio that provides the spark step-up voltage (in this example 10,000:1) provided the coil's core laminations are also intact. But, since few have the ability to measure inductance/capacitance and magnetic coupling efficiency (mutual inductance) is a BEAR to measure, things get simplified for the average mechanic by simply quoting primary and secondary resistance values...

Again, these are gross go/no-no specs that really only tell you if you've got a complete basket case. You already know the coil works, grossly. So, you either pull it and put it on a coil tester (good luck finding one today), or substitute another coil to see if that dramatically improves spark performance.

[Erv M.]

Re: Coil 1115270 Test Specifications

Duke,

I have two wires that are connected to the coil + side. One a light tan plastic insulated wire and the second is insulated with a braided clothe. You must forgive me as I am colored blind.

When cranking the engine the braided wire went to ground.

I do not think the coil is bad. This weekend I plan to replace the reproduction spark plug wires and check the plugs. I bought a new set of R45 plugs as I do not know what is in the car presently. Just for giggles bought a rotor cap and distributor cap if I need to go that route.

Miss the SoCal scene, hope all is well.

I have bought a new coil

Are you saying that the pink wires on the common terminal to the coil + side shorted to ground?

That wouldn't affect the coil.

You need to give a more precise description of exactly what short circuit occurred and whether you cranked the engine with the starter when the short was present.

Duke

[Duke W.]

Re: Coil 1115270 Test Specifications

Duke,

I have two wires that are connected to the coil + side. One a light tan plastic insulated wire and the second is insulated with a braided clothe. You must forgive me as I am colored blind.

When cranking the engine the braided wire went to ground.

I believe the "braided cloth" wire is the resistance wire that performs the same function as the ballast resistor on C2s. The other wire should be from the solenoid battery terminal and provides full battery voltage to the coil during cranking.

If the sheathed wire shorted to ground it carried more current than usual because that circuit normally has two resistances in series - the wire's resistance and the coil primary resistance.

Bottom line is that the short would have no effect on the coil. I believe their is a fusible link in one or both of the circuits, and that might have been damaged.

What I tried to do is visualize the circuit as it existed during the short and analyze what saw too much voltage or current. I don't have a '69 wiring diagram, but maybe you or someone else (Jack) could look at the diagram and run the same analysis.

Duke

[Clem Z.]

Re: Coil 1115270 Test Specifications

check the voltage to the coil and check the points for being burned