Coil testing are these good coils or not

[Dodge1934]

I have 3 coils . 2 are similar one is correct but couldn" t find it today and the forth is the condition of the original.

I  Have identified 6 spots on the coil and tested the resistance between all of them. Most were infinite resistance.  Both coils measured the same between similar points.

My ohm meter is old but i did put in a new battery.

When I touched the probes it measured 70 ohms

When I touched E to F it measured 70 ohms

When I measured across the resistor it also measured 70 ohms ...I took the resistor off to measure resistance.

Point A to D measured 400 ohms

point C to D measured 400 ohms

Oll other combinations were Infinity ( The needle didn`t move at all)

 

Are these coils good or do I need to do other tests?

[Bloo]

What are these coils for?

 

The construction looks VERY similar to the Buick "mailbox" coil, and there is a thread about it right now.

 

https://forums.aaca.org/topic/341214-delco-mailbox-coil/

 

The post on the outside you have labeled "to distributor" has to be spark out, in other words ignition wire to the center of the distributor. "Bat" is self explanatory. The only remaining wire has to go to the points ("Dimer" may be "timer").

 

The BAT terminal is not connected to anything, and just serves as a place to mount one end of the resistor and hot lead from the ignition switch.

 

26 minutes ago, Dodge1934 said:

When I touched the probes it measured 70 ohms

 

You really should zero the meter, but that wont really change the outcome here too much.

 

27 minutes ago, Dodge1934 said:

 

When I measured across the resistor it also measured 70 ohms ...I took the resistor off to measure resistance.

 

Sounds good, since the resistor is probably less than an ohm.

 

28 minutes ago, Dodge1934 said:

When I touched E to F it measured 70 ohms

 

Probably just case hardware, grounded when mounted on the car.

 

30 minutes ago, Dodge1934 said:

Point A to D measured 400 ohms

point C to D measured 400 ohms

 

That is a very good sign. A to D is probably the high tension winding. C to D is probably the high tension winding in series with the low tension winding. It isn't burned out. Thats about all you can tell with an ohmmeter.

 

To find out whether it works, you would need to make it work. The chances are good since it passed the ohm test. A car battery of the correct voltage could provide power. Use negative or positive ground depending on what the car uses. Hook a plug wire and plug from the high tension output (side terminal) through the spark plug to ground. Ground the coil (possibly unnecessary, but do it anyway). Hook a condenser from "dimer" to ground if the car uses an external condenser. For instance the Buick example above had the condenser inside the coil, and would not normally want an extra. I suspect the mailbox shape on the Buick may be to accommodate the condenser. Hook battery power to "bat" (goes through the resistor to "C"). Touch the bare end of a grounded wire  (with insulation on it so you don't get bit) to "dimer" and look for a good spark at the plug.

 

 

 

[Rusty_OToole]

If it checks out good and makes a spark you are not assured of a good coil. Sometimes they work when cold but fail when warm, such as, after being driven for half an hour or an hour. You can only say it is working when you put it on the car, and cross your fingers.

[edinmass]

You need to test it with a Herbrand coil tester under load. Coils will short when heated, and sometimes a partial short causes a poor spark..........go to YouTube and type in Herbrand HT-660 1950’s coil tester and watch the video. I have several vintage coils that test good with a meter, but fail when heated and loaded.

 

32 Packard coil getting tested today........

Edited March 23, 2020 by edinmass (see edit history)

[Dodge1934]

On 3/22/2020 at 4:28 PM, Bloo said:

What are these coils for?

 

The construction looks VERY similar to the Buick "mailbox" coil, and there is a thread about it right now.

 

https://forums.aaca.org/topic/341214-delco-mailbox-coil/

 

The post on the outside you have labeled "to distributor" has to be spark out, in other words ignition wire to the center of the distributor. "Bat" is self explanatory. The only remaining wire has to go to the points ("Dimer" may be "timer").

 

The BAT terminal is not connected to anything, and just serves as a place to mount one end of the resistor and hot lead from the ignition switch.

 

 

You really should zero the meter, but that wont really change the outcome here too much.

 

 

Sounds good, since the resistor is probably less than an ohm.

 

 

Probably just case hardware, grounded when mounted on the car.

 

 

That is a very good sign. A to D is probably the high tension winding. C to D is probably the high tension winding in series with the low tension winding. It isn't burned out. Thats about all you can tell with an ohmmeter.

 

To find out whether it works, you would need to make it work. The chances are good since it passed the ohm test. A car battery of the correct voltage could provide power. Use negative or positive ground depending on what the car uses. Hook a plug wire and plug from the high tension output (side terminal) through the spark plug to ground. Ground the coil (possibly unnecessary, but do it anyway). Hook a condenser from "dimer" to ground if the car uses an external condenser. For instance the Buick example above had the condenser inside the coil, and would not normally want an extra. I suspect the mailbox shape on the Buick may be to accommodate the condenser. Hook battery power to "bat" (goes through the resistor to "C"). Touch the bare end of a grounded wire  (with insulation on it so you don't get bit) to "dimer" and look for a good spark at the plug.

 

 

 

Thanks g

that is the type of detail I was looking for.... I will have to check into the condenser thing....

[Stude Light]

Just to be clear:

A - Timer not Dimer, that connects to the distributor (or timer) points and is part of the primary winding of the coil (ground side)

B - Battery, correctly stated above, that terminal provides no electrical path internal to the coil and only serves as a support to connect the battery wire to the resistor

C - That screw attaches the resistor to the input primary winding of the coil (battery side)

D - High tension (secondary winding) provides the high voltage spark and connects to the center terminal on the distributor cap

E - Mounting base (ground)

F - Holds the coil together, does not provide a voltage path

 

Resistance A-C is across primary winding

Resistance D-E is across secondary winding

You need to also check the coil resistor itself (remove screw C and test independently). I have found issues with the path from the resistor wire via the top through the screw due to corrosion.

 

The resistance measurements will give you an idea if you have a short or open but, as mentioned, to really understand if the coil is working you need a coil tester or a car to test it with.

Good luck

Scott

 

[Dodge1934]

Thanks for all the input.

greatly appreciated

 

Don

[Stude Light]

I measured up a known working Remy coil:

A-D: 1.2 ohms

D-E: 2.9 kilo ohms

Resistor unit: 0.5 ohms

That will give you a starting point. Below is from the Dykes Manual on testing the Remy unit

[Stude Light]

Edited March 31, 2020 by Stude Light (see edit history)