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08-28-2020, 04:07 PM | #1 |
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over heated coil
49 F1 with 12 volts, Bubba Chevy Distributor, internal resister coil, one Bosc, one NAPA-both over heat and the engine starts to miss and finally dies. voltage is in the 14 volt range. any ideas? do I have two bad coils? too much voltage?
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08-28-2020, 05:52 PM | #2 |
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Re: over heated coil
Check the primary resistance of the coil. Should be at least 3 ohms.
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08-30-2020, 05:39 PM | #3 | |
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Re: over heated coil
Quote:
This is important! It's also a very good test and a way to eliminate other unnecessary lines of testing. Once you know what the resistance is, you then can figure the amp draw (and heat) the coil is operating under. If you have a meter to check this,it's as simple as unhooking both primary wires from the coil and checking OHMS across the two coil terminals. It'll be good info to know. Terry
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"It don't take but country smarts to solve the problem" (Smokey Yunick) '41 Merc Town Sedan / 260" 8CM engine '66 Fairlane four door / "warmed up" 302 |
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08-28-2020, 06:01 PM | #4 |
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Re: over heated coil
The voltage should be in the 14+ volts range when running (12v setup). Are you sure you are using 12v coils? Like already posted, check the resistance of the coil(s).
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08-28-2020, 06:43 PM | #5 |
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Re: over heated coil
yes 12 volt coils--voltage on plus side is 14 volts, neg side is 9 volts, my other truck with a known coil runs 8.8 volts did not check resistance just got tired of messing with it, will do tomorrow. I strongly think I have two BAD coils, coil got so hot you could not touch it!
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08-28-2020, 06:45 PM | #6 |
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Re: over heated coil
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08-29-2020, 04:30 PM | #7 |
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Re: over heated coil
tried two more coils with the same results just exactly how hot does a coil get? these get so hot you cannot even touch them with out burning your fingers
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08-29-2020, 07:19 PM | #8 |
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Re: over heated coil
Not that hot. Do you have any idea what these coils are? It won't make any difference if they are all the wrong ohms.
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08-30-2020, 03:18 PM | #9 |
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Re: over heated coil
OK, I just about give up, have tried everything I know of and still cannot get this truck to run properly. everyone thinks it is ign. but I even tried another carb, another condenser and a coil off my other truck that was running a bubba dizzy. put one of the other coils I was trying on the 49 on the 41 truck and it ran with no problems. Got to be something I am missing but WHAT?
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08-30-2020, 05:10 PM | #10 |
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Re: over heated coil
If it is overheating then it about has to be too much current going through it. When you said the voltage was in the 14v range, was that at the coil? Did you check the voltage at the coil at around 2000 rpm? I'm guessing here, but the generator could be putting out too much voltage at rpm. Don't know if you run a generator or alternator, but it could be the same issue.
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08-31-2020, 11:42 AM | #11 |
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Re: over heated coil
One way to deal with it is to use an external ballast resistor. If they run too hot then they are drawing too much current. The ballast will bleed that off and keep the heat out of the coil. Ignition coils usually only fry themselves if the key is accidentally left on too long. A coil will always be pretty warm to the touch but it shouldn't be so hot as to burn you if you touch it.
Many manufacturers started using ballast resistors when the change to 12-volts came about in 1956. The 1.5-ohm primary type coil works well with a 1.3 to 1.5-ohm ballast. In later years, the epoxy resin insulation inside the coils allowed for a full 3-ohm primary resistance inside the coil. This eliminated the need for an external ballast for 12-volt systems. |
08-31-2020, 03:21 PM | #12 | |
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Re: over heated coil
Quote:
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08-31-2020, 05:00 PM | #13 | |
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Re: over heated coil
Quote:
Heat is energy and the energy to heat it up has to come from somewhere. |
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08-31-2020, 05:49 PM | #14 |
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Re: over heated coil
There is only one resistor in an ignition coil. It's called the primary coil. They are manufactured in various different ohm specification for various applications and most applications are voltage related. A person can measure the amps it is drawing with a multi-meter. Ballasts are used to control current flow but should only be necessary when it is drawing too much current. The old Ford V8 coils had to have a 0.8 ohm ballast to control the current flow on them since they were sensitive to current in the Mallory design.
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08-31-2020, 08:00 PM | #15 |
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Re: over heated coil
OK some of you guys are going off the deep end. turns out the alternator internal regulator was spiking voltage as high as 16 and this was causing most if not all the problem
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08-31-2020, 08:33 PM | #16 |
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Re: over heated coil
So, in order to check mine I put a voltmeter to the battery while it's running and then rev the engine to 2500 or so and see what the voltage is? I know it's supposed to be a bit over 14. I'll check mine in the morning.
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Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson) |
08-31-2020, 08:38 PM | #17 |
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Re: over heated coil
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09-01-2020, 07:19 AM | #18 |
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Re: over heated coil
I had to sit and wait for the voltage spikes, just did not go there and stay at 16 volts--up/down--repeat-repeat
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09-04-2020, 11:36 PM | #19 |
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Re: over heated coil
I have been through a lot of problems on the woodie this month with sputtering and missing on the hills. Not so much on the start of the trip to town (24 mile round trip), but the way home after she heats up. Tonight after sputtering on the long grades I popped the hood after I pulled into the shed. Here's what I found. Coil, So hot I could not keep my hand on, alternator 2" away was warm but could keep my hand on fine. Steel tube up to radiator, no way could I hold onto. Too hot. I don't have a lot of test equipment but do have a point and shoot temperature meter. I don't have a multi-meter but I do have a clear test light with a spike and a clip that reads volts on a green screen. Would that show these 'spikes' if that is also what I have and can anybody say what my temp gun should read on the coil? I can do more checking on the weekend. Thanks
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Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson) |
09-05-2020, 06:40 AM | #20 |
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Re: over heated coil
Instead of messing around till the cows come home you need to measure the current draw (AMPS) the coil primary is drawing with the engine running. To do this set your multi meter to DC AMPS scale which on most meters with this feature is 10 amps and insert your test leads into the common and amps sockets. Remove either of the coil primary wires and connect your meter in line between the coil terminal and the removed wire. With engine running you should have something like 3 or 4 amps draw reading. It will read a bit lower with higher revs. When you have done that report back. Regards, Kevin.
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