Ign coil temp (how hot)
- Thread starter billfish
- Start date
billfish
Senior Member
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.
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.
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.
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.
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.
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billfish
Senior Member
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.
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.
Attachments
rotorwrench
Well-known member
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.
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
Well-known member
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....
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....
BUBBAS IGNITION
Well-known member
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.
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.
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BUBBAS IGNITION
Well-known member
Actually I think when you short the lead wire you do both...??
billfish
Senior Member
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
Bill
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.
BUBBAS IGNITION
Well-known member
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.......
