Ign coil temp (how hot)

[billfish]

I seem to have another bad coil on my stock 51 8ba pos. ground Victoria. Engine seems to miss at cruising speed after a short run time, not at idle. A new Napa 6V Echlin (no resistor required) coil #904 corrected the problem for a while but it has returned. How hot should the coil get, it seems hot to the touch after a short run. It is properly connected with ign wire to - and +wire to dist.

[billfish]

More information-- with engine running
from - post on coil to +post on batt 5.2 volts

from + post on coil to - post on batt 3 volts

[JSeery]

Any idea what the coil resistance is? They get warm, but should not be extremely hot.

[Ross F-1]

That isn't a correct NAPA number, nothing shows with that. What I see for 6v flatheads on NAPA's site is either IC7, or IC7SB. Doesn't say anything about internal or external resistor.

[feelsharp]

6V coil should have a resistance of 1.3 to 1.6 OHMs. Some times coils are marked incorrectly and following battery ground does not work. Snyders sells a tester that plugs into the dissy and coil and indicates correct or incorrect wiring regardless of coil markings. I have had NAPA coils that were marked incorrectly.

[JSeery]

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As Ross said I checked NAPA and ECHLIN and nether list than number.

[billfish]

Here is a picture--must be an old piece

[JSeery]

LOL, interesting!!! Can't dispute that.

[billfish]

how do I measure the resistance. engine runs smooth, no miss for the first 10 to 15 minutes, as it heats up and I'm cruising at a steady speed in any gear I can feel it missing. This has happened before and I could correct it by changing condenser or coil. I think the new Napa coil is an IC7. I have a box with that number on it so I must have tried that coil also. But I was just wondering if the hot to the touch coil is an indication of what the problem is.

[BUBBAS IGNITION]

Originally Posted by billfish

More information-- with engine running
from - post on coil to +post on batt 5.2 volts

from + post on coil to - post on batt 3 volts

Numbers are numbers :

A battery voltage at coil of 5.2 volts is too low. Battery voltage should be 7.2 volts on a charging 6 volt system.
So our voltage is either low ( regulator issue /generator) or we have a voltage drop of 2.2 volts from the battery to the coil.
Lets worry about this first , get a voltage reading directly at the battery, if its low we need to fix that issue. If battery voltage running is 7.2 volts then we need to fix the voltage drop from the battery to the coil. Is there another resistor we are missing somewhere , like under the dash.

Then we can troubleshoot the coil....

[billfish]

Bubba thanks for your input--volts with engine running at batt is 6.3 and at coil neg terminal to batt pos terminal is 5.4

[billfish]

There is no external resister.

[Bob C]

When you are taking your voltage readings how fast is the engine running?

Bob

[billfish]

readings on coil in car and spare coil

both the same

coil + to - terminals --1.5 ohms on both coils

coil + or - to center post on coil== 9,900 ohms on both

I think i'm doing this right, but it looks like my battery reading at 6.4 with engine running is to low should be 7.2

[billfish]

Bob good point- when I rev the engine the voltage at coil goes to 7.2 volts

[koates]

Something to understand with generators is they do not charge at engine idle like an alternator does. All voltage readings should be taken with the engine revved up to around 2,000 RPM. Voltage of a charged 6 volt battery at rest or engine idle should be approx. 6.3 volts. With engine revved up the voltage across the battery terminals and at other places in the cars circuit should be at least 7.2 volts and preferably 7.5 volts. When taking these voltage readings it requires some little time for the voltage to rise up to the set reading, say around 2 or 3 minutes, especially if you are testing after a cold start. Regards, Kevin.

[billfish]

So at 2,000 rpm I have 7.2 volts at the coil. I guess I'm back to square one, is the coil getting to hot for some reason or is this normal. It's more than warm, I would call it hot but not enough to burn your hand?

Do the resistance readings I posted above look normal? Appreciate the help.

[flatjack9]

With your readings, you have about 4.8 amps at the coil. That is too much. You want it down around 3 amps. You need more resistance in the system.

[G.M.]

Originally Posted by billfish

So at 2,000 rpm I have 7.2 volts at the coil. I guess I'm back to square one, is the coil getting to hot for some reason or is this normal. It's more than warm, I would call it hot but not enough to burn your hand?

Do the resistance readings I posted above look normal? Appreciate the help.

7.2 at the coil is to high if the coil doesn't have a built in resistor. Try
different resistors to get the voltage down to 4.0 volts or enough resistance
until it runs a little ruff then lower it a little. The coil will run cooler when
you get the voltage down. G.M.

[koates]

The ideal coil primary winding current draw should be around 2.5 to 3 amps which will give the distributer contact points a fairly long working life. A 4 amp or more current draw would be too high. To achieve this 3 amp current draw with approx. 7+ volts powering your system requires a specific resistance of the coil you choose to use and plus if required an external resistor in series with the coil primary winding. With 7 + volts the resistance in the coil primary circuit needs to be approx. 3 ohms either made up of the coil alone or the coil plus a resistor. Your two coils you tested were 1.5 ohms each across the primary. You could use either one of these coils but need to add a 1.5 ohm resistor in the coil supply. A good final test is to fit an accurate (preferably analogue) TEST AMMETER (not a dash ammeter) in series with the coil battery supply and run the engine from idle to speed and hopefully read an approx. 3 amp current draw. You can mess around with coils, resistors, and voltage readings till the cows come home BUT in the final analysis the primary coil windings need a 3 amp current draw and no more! The reason your coil is getting very hot is that the current in amps drawn by it is too high. Regards, Kevin.

[BUBBAS IGNITION]

Looks like koates hit it on the head.

You need to add some resistance ( 1.5 ohms or a little less) . 1.5 coil winding and a 1.5 resistor (our RU11T resistor checks at 1.2-1.5 ohms) will give you approx 2.4-3 amps.

The other issue is by dividing the resistor into two 1.5 ohm unit the wattage ( heat) is divided . Thats the way it should be , should solve your heat issues.....

Als the lead wire from the coil to the distributor should be a finely stranded lead wire to drop the final voltage to protect the points......

[rotorwrench]

A lot of these old systems are sensitive to excessive use of the ignition switch when the engine is not running or if someone forgets to turn off the ignition and it runs the battery down. If the points happen to be closed, the coil turns into an electromagnet and can get very hot. A lot of them bite the bullet from this type of incident.

The OEM coils on the 8BA Load-O-Matic ignition system had 1.05 to 1.15 Ohms primary resistance and a 4100 Ohm secondary resistance. With that and the OEM distributor wire that Bubba mentioned, the system would function as designed. Any changes to the system will have an effect that would likely be detrimental. If a person can't find a proper coil, a ballast resistor would be the only recourse.

[billfish]

I have ordered a new coil and condenser from Mac's for a 1951 8ba and would expect it to be the correct pair for my engine out of the box. Does this sound like a proper fix to you all. I'm hoping this corrects the miss (hesitation) I experience when under load at any cruising speed. Engine idles fine no miss, I have replaced dist cap and rotor, also set dwell at 27 degrees, adj carb and timing. I surely appreciate all the help, thank you-Bill

[JSeery]

No personal experience, but there are a lot of reports of new condensers being bad from the get go.

[rotorwrench]

X 2. The manufacturer's don't care if they work or not. They let the customer find out. I've pulled more than one pig tail out of those types without much force & found that they weren't even soldered. The materials might even be OK but manufacturing technique is off on some. At some point we may have to roll our own and stuff them in a home made can. A little trial and error with a capacitor tester and we might finally get some decent spark.

In the mean time, a person has to order 3 to get at least one half ways decent one. The IH 200 was good for a long time but manufacturing is going to change now that Standard owns Echlin. The high dollar Scintilla Vertex magneto capacitors might be the only good ones left.

[JSeery]

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Originally Posted by rotorwrench

At some point we may have to roll our own and stuff them in a home made can. A little trial and error with a capacitor tester and we might finally get some decent spark.

I like the idea discussed a while back with the "homemade" capacitor in a brass case. Any additional information on that?

[koates]

billfish, Read again my post #20 and UNDERSTAND it. Regardless of which coil and which resistor you purchase and fit to your car, you have to do the amps current draw test with a TEST AMMETER and only then will you know the parts purchased are working correctly or not. Just guessing on components is not the way to do it. TEST, TEST, TEST and read the AMPS which should be 2.5 to 3 amps draw on the coil primary circuit and NO MORE. These suppliers will sell you anything and would not have a clue if they are going to work correctly. DO the TEST. Regards, Kevin.

[JSeery]

Very good advice koates!

[billfish]

Koates and Jseery- I'll get a test ammeter and check for amperage. I have a AW SPERRY DM-8300 DIGITAL MULTIMETER I use in my air conditioning work but not sure it will read amperage on the car circuit.

[billfish]

Koates--Jseery -when you say (in series with the coil battery supply)-exactly from where to where do I take this reading?

[G.M.]

Originally Posted by JSeery

I like the idea discussed a while back with the "homemade" capacitor in a brass case. Any additional information on that?

I'm the one that described putting an IH-200 in the Ford condenser
shells. It's difficult and takes time. The best and easiest way is to
mount the IH-200 from Napa to the coil. Use one of the coil mounting
screws on the passenger to hold and ground the condenser. On the 39
type use a screw to hold the pigtail terminal to the brass tab on the
bottom of the coil. On the 36 type coil Put a screw though the hole
in the back of the coil where the condenser is held into the coil. Put on
a lock washer and nut and tighten good. Put the condenser lead terminal
on and another lock washer and nut and your condenser problems will
be over. G.M.

[koates]

billfish, The test ammeter goes in series or inline in the coil primary. Remove the power wire from the ignition coil pos + terminal and connect one ammeter test lead to the removed wire and the other ammeter test lead to the coil + terminal that you removed the wire from. Do the test with the engine running at different speeds. If you do the test just with the ignition "ON" and engine not running the amps current draw will be higher than with the engine running. Engine running is the important test with no more then 3 amps draw. 2.5 amps would be great. Regards, Kevin.

[koates]

billfish, I see your ford is still POS ground so connect your test ammeter into the ignition coil negative terminal which is the power supply wire from the ignition switch. Regards, Kevin.

[billfish]

Kevin-- With digital multimeter connected in series with neg ter on coil (wire from ing) and disconnected wire I get 1.9 amps at idle and the number goes down as I rev engine to belown 1.

[billfish]

Here's a picture of the meter I'm using and the connections and setting.

[billfish]

disreguard 9 volt batt note on meter--that's just to remind me what powers the meter.

[billfish]

Attached is a picture of the coil that I'm using.

[koates]

bill, That number seems a little low but if your ford is starting and running and pulling OK at speed then leave it. Did you just run the coil pictured without a resistor ? Regards Kevin.

[BillM]

I'd be interested to see what the current is through the coil with the engine off and the wire from the coil to the distributor disconnected and your meter connected from the coil to ground. Set the meter to DC current and touch the pos lead to ground with the ignition on. Just leave it on long enough to get a reading, then shut off the ignition.
Do you have the temperature probe for the meter? If so you could take the temp of the coil.
It would be a good idea to check the dwell of the distributor too.

[rotorwrench]

As an electro magnet (engine off & Ign key on), they can pull around 5 amps with no added ballast. It just depends on the primary resistance. I would prefer a mechanical amp meter with a needle swing. The digital meter may have some built in shunting that may affect a series connected line reading.

[koates]

BillM, I cant really see the point in your coil test because the coil would not be in a working situation, so not much value there. Regards, Kevin.

[BillM]

Well there are lots of posts that use Ohms law to compute coil current so I would like to see how an actual measurement would compare. The readings taken with the engine running are of pulsating DC so do not relate directly to the computed values.

[billfish]

Koates--The engine starts and runs ok--but misses under load--in the past I could correct this by changing condensor or coil. Waiting for new coil and condensor. Will take amp. readings with new parts.

Billm--dwell is set to speck (27 degrees). What should the temp of the coil be, seems to run very hot-I will check it's temp tomorrow.

[koates]

Originally Posted by BillM

Well there are lots of posts that use Ohms law to compute coil current so I would like to see how an actual measurement would compare. The readings taken with the engine running are of pulsating DC so do not relate directly to the computed values.

Yes BillM you are correct. BUT computed calculations using ohms law are all good but only approximate and not the actual readings and therefore not necessarily useful in knowing the facts. The pulsating DC caused by the distributer contacts opening and closing has the effect of lowering the coils current draw only when the engine is running. I am trying to deal with Bills problem here so don't want to comment too much with other comments. Regards, Kevin.

[G.M.]

Originally Posted by billfish

Bubba thanks for your input--volts with engine running at batt is 6.3 and at coil neg terminal to batt pos terminal is 5.4

This whole thing boils down to the voltage to the coil is to high which
is why the coil gets hot. You need 4.0 at the coil when engine is
running with enough RPMs so the generator is charging. With the engine
running at say 20 MPH the battery voltage should be 7.2. Coil voltage
much over 4.0 volts and the coil will get hot. Coil voltage much below 3.5
volts and the engine will start to miss, very simple. Correct the voltage
problem before you start putting on new parts. G.M.

[billfish]

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G.M.
the 51 ford does not use an external resister, what component in the ignition circuit would cut the voltage to 4.
Bill

[G.M.]

Originally Posted by billfish

G.M.
the 51 ford does not use an external resister, what component in the ignition circuit would cut the voltage to 4.
Bill

Bill I'm into the engines mostly before 1949. The 48 I guess was he last external resistor until 12 volts came and the big white resistor was used for a few years.Your battery is still
6 volts and not 8 volts I assume? For some reason you seem to have to high of voltage at the coil. G.M.

[billfish]

Battery is 6 volt- system is stock 6 volt pos. ground-stock 51 fords do not use an external coil resister.
installed new coil and condenser today, readings on new coil,
pos. to neg. 1.5 ohms--------pos. or neg. to center post 8.78 ohms. Numbers look about the same as the two old coils.
Voltage reading at coil neg terminal with engine running at 1,200 rpm is 7.2 volts. Bubba in post #10 said this would be correct.
Amperage from coil neg. terminal to disconnected wire from coil neg. terminal reads 2 amps at idle and goes down as rpm's increase. Coil temperature is about 135 degrees after 30 minute run time. Engine idles fine (no miss) but stumbles under load in any gear at any speed.
Attached is a picture of new coil.

[rotorwrench]

Billfish
The secondary resistance you mentioned is too low. The stock Ford 7RA-12029-A coils had near 4100 Ohms of resistance between the joining terminal (the DIST or Neg terminal on the side) and the center high tension lead post terminal. On the negative ground cars of the more modern era, the Neg terminal was the distributor/points connection and that end of the primary was directly connected to the secondary winding but now days it could be connected to either terminal plus you have a modern coil going into an older positive ground car. A person needs to purchase a coil tester or use the pencil test to see if the polarity is correct. Simple polarity testers are available from some of the antique parts suppliers. The system will function but not be efficient if the coil polarity is incorrect.

There seems to be a fixation on one cause for your problem when it may not even be ignition related. You are correct to assume it might be though. There are a number of factors that can cause problems under load. A fuel pump that has poor output is one and a bad power valve in a 48 type carburetor is another so you can't rule anything out until you are positive that your ignition system is functioning normally. A coil has to be tested with special equipment or at least someone with an oscilloscope to check the system while running. The condenser has to be tested for capacity and leakage with a capacitor tester to be certain it is working correctly. The Load-O-Matic distributor can get worn bushings that can give all sorts of intermittent dwell problems with the points, the vacuum can can leak and not give the intended spark advance needed, and last but not least is the two wire circuits that connect things internally and externally for good grounding and breaker action might have problems or be incorrect parts. All this distributor stuff can be checked out by someone with the proper equipment so you would know for certain whether this is your problem or not. If you have factory overdrive, there can be some intermittent problems with that system since it is designed to ground the coil for kick down.

Echlin (from NAPA) was purchased by the company that owns Standard Motor Parts recently so there is no telling what part number coil is available from them these days. The old tried & true replacement was the IC7. IC7 stood for Ignition Coil number 7. If this coil is no longer available then we all may have to make some changes in the future.

[BUBBAS IGNITION]

Guys this post has been driving me nuts as i know the input voltage is too low , using a volt drop test we know we are loosing voltage to the coil from the ignition switch. Yesterday while discussing this to a Ford club member who has restored a few early fords.
His statement was no the 50 dont use a ballast but it does use a "loom" resistor from the switch etc.
The loom is used as a special harness wire to drop the voltage going to the coil. I think thats the issue we have here....

[Ross F-1]

These are the specs for a 49-51 Truck. I have never seen any note in the manuals or parts listings to indicate a resistance wire was used to feed the coil, and no external ballast resistor was used.

[BUBBAS IGNITION]

Just talked to billfish and he thinks the car is fixed !!! The fix was to polarize the voltage regulator./ generator?
Ya got to think about this one.
If a coil is ran in reverse polarity for any given time the steel laminates will assume the magnetic polarity etc. If reversed then the coil will loose approx 80% of the coil output. Still start just wont rev up as acceleration needs extra voltage from coil. Incorrect polarity would cause this.

[Ross F-1]

Was his ammeter showing Discharge instead of Charging?

[Bob C]

I though you polarized the generator not the voltage regulator.

Bob

[BUBBAS IGNITION]

Originally Posted by Bob C

I though you polarized the generator not the voltage regulator.

Bob

Actually I think when you short the lead wire you do both...??

[billfish]

I believe I was polarizing the generator from the connections at the voltage regulator, this is the way I read to do it. And yes the ammeter on dash was showing that it was charging and the battery always maintained a full charge. I have my fingers crossed, but the car is now running smooth on acceleration and the difference is dramatic. Thanks again to Bubba, and everyone else that put up with my repeated posts on this problem. I had disconnected the battery a few weeks back and I guess this caused the problem.
Bill

[koates]

BOY! This story is really getting screwed up ! BUBBA, he said the voltage at the coil input was 7.2 volts with engine running so why do you say that is too low ?? Also this generator polarizing story is a load of bulls..t. The generator has been charging OK all along and therefore would not require to be repolarized would it. The battery fitted to the car has always been positive to ground. Disconnection of the battery for a week or ten will have no effect on the electrical system. If you disconnected the battery for 5 years and did not run the car it might effect (loose) the residual magnetism in the generator field coil pole shoes and only then would the generator need to be repolarized. Seems like the original fitted coil might have been down on high tension output because the only thing that has been changed is the new ignition coil and CONDENSER which according to the owner has fixed the problem. These problems are hard to fix on the internet because owners don't always give the exact information required or have the required test equipment at their fingertips. Pleased its fixed. Regards, Kevin.

[Ross F-1]

Exactly right, Kevin.

[BUBBAS IGNITION]

Originally Posted by koates

BOY! This story is really getting screwed up ! BUBBA, he said the voltage at the coil input was 7.2 volts with engine running so why do you say that is too low ?? Also this generator polarizing story is a load of bulls..t. The generator has been charging OK all along and therefore would not require to be repolarized would it. The battery fitted to the car has always been positive to ground. Disconnection of the battery for a week or ten will have no effect on the electrical system. If you disconnected the battery for 5 years and did not run the car it might effect (loose) the residual magnetism in the generator field coil pole shoes and only then would the generator need to be repolarized. Seems like the original fitted coil might have been down on high tension output because the only thing that has been changed is the new ignition coil and CONDENSER which according to the owner has fixed the problem. These problems are hard to fix on the internet because owners don't always give the exact information required or have the required test equipment at their fingertips. Pleased its fixed. Regards, Kevin.

My biggest concern all along as well as some others was the voltage drop before the coil. We wasnt discussing the charging at that time, someone up a post or two said they should check the coils polarity.
When a post goes this long it should be flushed , too many opions to help anyone.......

[Bluebell]

Kevin, I do hope you're still here answering questions when I need some serious advice on electrics.