| louganser | -- 07-06-2010 @ 5:38 PM |
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I just received a new coil to replace the defective one. Are there any specific steps to be followed when replacing the coil (other than disconnecting the two wires and the lead wire) and installing the new unit? Lou G
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| 37RAGTOPMAN | -- 07-06-2010 @ 5:53 PM |
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Just check to make sure the coil is receiving the correct amount of voltage. I think about 3 1/2 to 4 volts,it should have a resister to lower the voltage, if not that is why the old coil is defective and not good anymore, The resister should be under the dash on the firewall. 37RAGTOPMAN KEEP ON TRUCKIN,,,,!!!!!!!!
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| deluxe40 | -- 07-06-2010 @ 7:43 PM |
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The '46-'48 book notes on page 5-11 that the ballast resistor was "relocated to a fiber board device that mounted over the coil top terminals". This was done on the V8 cars at the time that the H-series six cylinder engine was introduced in 1947. Consequently, there should be a ballast resistor mounted on top of the coil in '48. If it isn't there, you might have found the reason the coil failed.
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| supereal | -- 07-07-2010 @ 10:10 AM |
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My '47 was made in late August of that year, and still had the ballast resistor on the firewall. Most 48's had them on the input terminal of the coil. The resistor is important as a sort of voltage regulator that prevents overheating the coil, as well as protecting the points. Just be sure that your new coil doesn't have a built in resistor, as we have seen one of those in an aftermarket repro.
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| oldford2 | -- 07-07-2010 @ 2:20 PM |
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If you check the voltage with just the ignition on you may get 6 volts. Start the engine so the resistor can warm up and do it's job - reduce voltage to 3 1/2 to 4 volts. This allows 6 volts to the coil for starting and then cuts back to 3-4 volts for running so the points don't burn too soon. Properly maintained, this is the best ignition system for these flatheads. John
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| louganser | -- 07-07-2010 @ 2:49 PM |
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There was nothing mounted on the top of the coil. What does a rsistor look like? Is it tubular, approx. 1.5 inches long with a wire? Lou G
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| supereal | -- 07-07-2010 @ 3:03 PM |
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It is mounted on the firewall. It is a tubular unit with a slotted metal cover. You can see a picture on page 150 of the C&G online catalog. www.cgfordparts.com Sometimes it will be mounted on the same board as the headlight circuit breaker, also shown on that page.
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| 39 Ken | -- 07-08-2010 @ 5:20 AM |
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Bob, To clarify, "mounted on the firewall"; means that it's mounted on the inside of the firewall, under the dash, like the cars thru '47. Ken
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| TomO | -- 07-08-2010 @ 7:11 AM |
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If you have the trumpet horns mounted on the left inner fender, your resistor will be mounted on the inner side of the firewall and will have a red / black wire connected to one side. With the sea sh*ll horns, the resistor is mounted on the coil. The 48 Ford should have the sea sh*ll horns. Tom
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| 48Tudor | -- 07-08-2010 @ 7:28 AM |
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The resistor will have TWO connections on it. If you see something metalic, tubular, with one wire coming from the end, that will be a condenser. Normally mounted on the Dist., but could have been put on the coil.
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| Steve's 48 Ford | -- 07-08-2010 @ 8:44 AM |
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My 48 has the resistor is mounted on top of coil. Joe's Antique Ford parts in Uxbridge, MA has them 1-800-508-3980. Part Number 18-12250 for $6.00 Good Luck
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| supereal | -- 07-08-2010 @ 9:40 AM |
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Right, Ken. I left out the important "inside of" on my post. A weak point on both original and repro ballast resistors are the end terminals that connect to the nichrome element. The constant heating and cooling of that winding will often cause the crimped connections to loosen. They need to be solidly crimped, and soldering them is recommended. A very small added resistance will lower the voltage to the coil by enough to prevent easy starting and poor operation under load.
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| louganser | -- 07-08-2010 @ 3:21 PM |
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Thanks! I looked thru several catalogs and found it under the dash. I tested it with a meter and it registered a full 6 volts. I've ordered a new one. Lou G
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| 39 Ken | -- 07-08-2010 @ 6:21 PM |
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OldFord2 mentioned it but here it is again. The resistor is supposed to be at a full 6V when cold. Start the engine and let it run. Check the voltage again. As the resistor warms up, the voltage will drop to around 3.5 v. Ken
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| supereal | -- 07-09-2010 @ 9:55 AM |
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The voltage reading of the resistor, and any other part of the system, is load dependent, as voltage is the product of current times resistance. That is why the input to the coil reads the same as the battery when the points are open and the coil isn't drawing power.
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| louganser | -- 07-17-2010 @ 2:33 PM |
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Thanks for all the tips! I found a NORS resistor at a old time parts shop in my town. When I removed the old one, I found that the ceramic rod was cracked. After installation, I had approx. 3.5 volts. Lou G
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| 47Fordor | -- 07-18-2010 @ 5:42 AM |
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When it comes to stuff like resistors, I believe "when in doubt, replace it." I don't believe you would get any bonus points in judging for having an original resistor, they're not that expensive, and you probably just saved yourself a coil (which is a good bit more expensive). Chris
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