05-01-2019, 08:04 PM | #1 |
Senior Member
Join Date: Apr 2016
Location: St Clair, Michigan
Posts: 395
|
6V coil issue
My car was idling in the driveway on Sunday for around 10 minutes to warm it up before going to a car show and it completely and abruptly shut off without sputtering or anything. I checked all the usual culprits and got to the coil which was showing no power and nobody had one in my town on Sunday so I had to wait till Monday to get one.
My question is somethings still does not seem right or maybe it is working as it is supposed to that when I use my test light with the voltage readout on the side everything has 6 volts when the key is on but when I test it at the coil output that goes to the top of the distributor cap it only has 2.3 V to 2.5 V Whether the key is on or off? Is that normal or is something wrong?
__________________
Isaiah B. 1928 all metal Tudor |
05-01-2019, 08:24 PM | #2 |
Senior Member
Join Date: Jul 2018
Location: Spring Grove, Illinois
Posts: 1,371
|
Re: 6V coil issue
Is it an original or repro coil?
__________________
"The more things change, the more they stay the same." |
Sponsored Links (Register now to hide all advertisements) |
|
05-01-2019, 08:54 PM | #3 |
Senior Member
Join Date: May 2010
Location: Young Harris, GA
Posts: 1,819
|
Re: 6V coil issue
Isaiah, if you want to take voltage readings on the ignition system, you need to temporarily remove the rotor and slip something that does not conduct electricity between the points. I use a business card. Then you can read voltage at any point between the points and the other side of the coil and you should see 6 volts.
It is not normal to read voltage on the wire that plugs into the top of the distributor cap. But if the car runs OK, I would not worry about it. Make sure you have the polarity of the new coil hooked up correctly, to match the ground that you are using on the battery. If you have the coil polarity backwards, the engine will run but not as well as it will when the coil is hooked up properly.
__________________
Jim Cannon Former MAFCA Technical Director "Have a Model A day!" |
05-02-2019, 08:01 AM | #4 |
Senior Member
Join Date: Apr 2016
Location: St Clair, Michigan
Posts: 395
|
Re: 6V coil issue
It’s about two years old from advance auto parts. But it probably has three hours of run time on it total.
__________________
Isaiah B. 1928 all metal Tudor |
05-02-2019, 08:03 AM | #5 | |
Senior Member
Join Date: Apr 2016
Location: St Clair, Michigan
Posts: 395
|
Re: 6V coil issue
Quote:
And I will make sure I stick a business card in between the open points and check it all again.
__________________
Isaiah B. 1928 all metal Tudor |
|
05-02-2019, 08:29 AM | #6 |
Senior Member
Join Date: Aug 2018
Posts: 2,332
|
Re: 6V coil issue
Sponsored Links (Register now to hide all advertisements)
Ignition off, remove fuse or disconnect battery. Remove all 3 leads from the coil. Measure across the coil small two terminals - 6v coil should be 1.5 ohms. 12 v - 3 ohms Measure each terminal to the coil to distributor output socket - 10K to 14 K ohms. With battery connected fuse installed, all leads connected to the coil. Open the points as Jim suggested both sides of the coil should be 6v on the meter to ground. Close points (or jumper across the points) and one side of the coil will be 6v, the other side is 0V. Rotor installed, cap and body installed, nothing between the points, coil wire installed.. Remove coil wire at distributor, place free end 1/4 inch from a clean head nut. Place piece of cardboard under the free end of coil wire over to the stud to keep sneak spark path through paint from happening. With ignition on, crank starter, should see a nice strong blue spark. If real weak or yellow - check connections, try checking point gap, and clean points. Try again. If still not good spark possible bad/marginal connections or weak bad coil. |
05-02-2019, 10:16 AM | #7 |
Senior Member
Join Date: Jun 2015
Posts: 1,414
|
Re: 6V coil issue
If a new repro coil, check if oil filled by shaking it. Some of these are recommended to be installed with the leads on top rather than downward for full internal windings coverage. The original tar/ paste or new epoxy coils can be mounted terminals- down like stock.
Also, 30closedcab test values may indicate an internal resistor if the packaging is unclear. |
05-02-2019, 10:17 AM | #8 |
Senior Member
Join Date: Dec 2016
Location: Sunrise Beach, Mo
Posts: 439
|
Re: 6V coil issue
A coil used on a 12 volt vehicle that has a limiting resistor is actually a 6 volt coil. I have run Primary resistance checks to validate. Just FYI.
|
05-02-2019, 10:20 AM | #9 |
Senior Member
Join Date: Jun 2015
Posts: 1,414
|
Re: 6V coil issue
|
05-02-2019, 11:25 AM | #10 |
Senior Member
Join Date: Aug 2018
Posts: 2,332
|
Re: 6V coil issue
Some use a 6v 1.5 ohm coil with a 1.5 ohm ballast resister to give total of 3 ohms when used on 12v systems. Configured this way the coil and resistor share the heat dissipation, so the 6v coil runs much cooler than a 12 v coil with a internal resistance of 3 ohms.
Theory is they are the same package and have the same ability to dissipate heat. Less chance of the 6v coil /ballast failing in comparison to the 12v coil. Last edited by 30 Closed Cab PU; 05-04-2019 at 09:14 PM. Reason: Mistake correct 12v resistancce form 6 ohms to 3 ohms |
05-02-2019, 11:40 AM | #11 |
Senior Member
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 1,144
|
Re: 6V coil issue
Umm. Both coils consume the same power (6V x 4A vs. 12V x 2A) which means they both dissipate the same amount of heat. The added resistor is an extra heater, consuming the same power as the 6v coil.
|
05-02-2019, 11:57 AM | #12 |
Senior Member
Join Date: Aug 2018
Posts: 2,332
|
Re: 6V coil issue
6 V, 6v coil, 1.5 ohms - current 6/1.5 = 4 Amps, Coil Wattage 4 x 6 =24 watts
12 V, 12 v coil, 3 ohms - current 12/3 = 4 amps, Coil Wattage 4x 12 = 48 watts 12 v, 6 v coil with 1.5 ohm ballast, - 6 volts drops across the coil of 1.5 ohms and 6v drops across the ballast 1.5 ohms, current is 4 amps 12/3. Wattage coil is 6 X 4 = 24 watts, Wattage ballast is 6 x4 = 24 watts. |
05-02-2019, 03:40 PM | #13 |
Senior Member
Join Date: Aug 2018
Location: Foley, Al
Posts: 142
|
Re: 6V coil issue
Isaiah do you attend the Model 'A' garage meet at Charlie's barn in Sarasota? If so I'll be there next week and will be bringing in a coil / condenser tester I recently built. It's kind of like a Model 'A' ignition simulator.
__________________
Jim |
05-02-2019, 10:01 PM | #14 | |
Senior Member
Join Date: Apr 2016
Location: St Clair, Michigan
Posts: 395
|
Re: 6V coil issue
Quote:
I still do that 5am to 5pm work stuff. Al Leach invited me last weekend as well. One of these days I promise I’ll make it.
__________________
Isaiah B. 1928 all metal Tudor |
|
05-02-2019, 11:25 PM | #15 | |
Senior Member
|
Re: 6V coil issue
Quote:
Are you sure you are feeling ok? You sound like you have a 24Hr bug coming on.
__________________
What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II |
|
05-03-2019, 10:10 AM | #16 | |
Senior Member
Join Date: Jun 2015
Location: Red Deer, Alberta
Posts: 5,043
|
Re: 6V coil issue
Quote:
__________________
If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn! |
|
05-03-2019, 12:16 PM | #17 |
Senior Member
Join Date: Apr 2016
Location: St Clair, Michigan
Posts: 395
|
Re: 6V coil issue
Ugh ugh cough cough. I think your right I better stay home until Wednesday.
__________________
Isaiah B. 1928 all metal Tudor |
05-03-2019, 01:42 PM | #18 | |
Senior Member
Join Date: Aug 2018
Posts: 2,332
|
Re: 6V coil issue
Quote:
I agree, you are right since the points are only closed part time. I used this as an example. Still a 12v coil vs. the 6v coil with ballast comparison , the 12 v coil will run warmer. |
|
05-04-2019, 11:33 AM | #19 | |
Senior Member
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 1,144
|
Re: 6V coil issue
Quote:
|
|
05-04-2019, 12:38 PM | #20 |
Senior Member
Join Date: May 2010
Location: Alabama
Posts: 8,099
|
Re: 6V coil issue
I have used a three OHM Pertronix flame thrower coil on my 12 volt converted model A roadster for 12 years with excellent results . This is a performance coil that gives instant starts and performance that can be felt . Pertronix also offers a 1.5 version of this coil for 6 volt use . I haven't seen any three OHM coils offered by model A venders . It will no doubt be easier to get a good three OHM direct than just walking in a local parts house and asking for a three OHM coil . Usually the counter man won't know the difference and will ask what model and year car the coil is for . If you say it is for a model A Ford that is probably as far as you will get with that .
|
05-04-2019, 02:13 PM | #21 | |
Senior Member
Join Date: Apr 2016
Location: St Clair, Michigan
Posts: 395
|
Re: 6V coil issue
Quote:
Great world we live in these days... sigh Thanks for the heads up on the flame thrower coil. I’ll ya e to check that one out. And have one as a spare as well.
__________________
Isaiah B. 1928 all metal Tudor |
|
05-04-2019, 04:59 PM | #22 |
Senior Member
Join Date: May 2010
Location: Alabama
Posts: 8,099
|
Re: 6V coil issue
I forgot to mention that the epoxy filled coil is the best bet for the model A . The epoxy coil can be mounted and run with the wire connections at the bottom . The oil filled coil is best mounted with the wire connections at the top or the coil can over heat and fail early . . This may not pertain to a performance coil . Others have mentioned coil problems with the coil being hot to the touch . Use of an oil filled coil on the model A can be problematic after a while if not mounted correctly .
|
Sponsored Links (Register now to hide all advertisements) |
|
05-04-2019, 09:11 PM | #23 |
Senior Member
Join Date: Aug 2018
Posts: 2,332
|
Re: 6V coil issue
|
|
|
Sponsored Links (Register now to hide all advertisements) |
|