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EFV-8 Club Forum / 1940 Ford Discussion / Ballast resistor

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Posted By Discussion Topic: Ballast resistor     robert993 08-04-2013 @ 4:31 PM reply profile send p.m. Member Posts: 33 Joined: Sep 2010 I was told by a flathead Ford mechanic that the ballast resistor could be bypassed by connecting both wires to one of the terminals, and this would prevent a failing resistor from causing problems. He also said that if the ignition has not been converted to 12 volts, there was no danger in burning the points, since Ford eliminated the resistor in 1949. Has anyone heard of this and what is your opinion? kubes40 08-04-2013 @ 5:47 PM reply profile send p.m. Senior Posts: 3368 Joined: Oct 2009 Bypass the resister and you'll be sending a full 6v. to the distributor. Points and / or condenser will very soon fail. Ford got rid of the external resistor in '49.- that's true. They placed it within the coil. In other words, the resistor is still there, it is simply not in "plain sight". Your mechanic is so far off on his advice I might suggest you "shop elsewhere". TomO 08-05-2013 @ 8:14 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 The ballast resister is needed if you are running a stock pre 1949 coil. Bypassing the resister will result in your coil overheating and eventually burn the points. If your car is 12 volts or running with a 1949 or later coil, you must check with the coil manufacturer to determine if an external ballast resister is required. Most of them have an internal resister. The ballast resister is the most reliable component in the ignition system. Many cars are still using the one that the car was manufactured with. Tom shogun1940 08-05-2013 @ 9:53 AM reply profile send p.m. Member Posts: 464 Joined: Feb 2010 I am not sure about resistors in the coil,but i do know when they went to 12v resistors were replaced with resistor wires so we do need them. Some racers installed switches to give a full 12 or 6 volts for racing or starting . supereal 08-05-2013 @ 10:06 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Many 12 volt cars were manufactured with 6 volt coils. Either the ignition switch or the solenoid applied 12 volts to aid starting. Then, when the starter was done, 6 volts was returned to the coil. Most, if not all, 6 volt round coils have a built in resistor. If not, resistor wire would be required. The main purpose of the original Ford resistor is to function as a voltage regulator. As the engine speed increases, the charging volatge varies. To prevent burning up points and coil, the resistor, as it gets hot, reduces the voltage. They do get hot, as anyone who touched one when it was running well knows. The resistor, as a separate unit, was eliminated in 1949 when the "post hole" distributor arrived. ford38v8 08-05-2013 @ 6:04 PM reply profile send p.m. Senior Posts: 2735 Joined: Oct 2009 Bob, yes, they do get hot! When I was a kid, someone told me to put a quarter across the terminals to make my '39 run better. That day found me upside down under the dash, engine running, quarter in hand. I never found out if the engine ran better, but I sported a likeness of George Washington on my index finger for a week! Alan 56MarkII 07-13-2019 @ 1:12 PM reply profile send p.m. Member Posts: 63 Joined: Jan 2012 Yes this is an old thread but some things do not make sense! Why would Ford eliminate the resistor in 1949?? Why would they also have an internal one?? The reason for the external resistor was so it could be bypassed during cranking to increase the voltage lowered during cranking. The newer Ford products have a resistor bypass in the starter solenoid which is the extra terminal wired to the ignition terminal of the coil. My 1950 Mercury only has one terminal on the metal cased solenoid and there is an OEM looking wire running to a relay bolted to the driver's side inner fender. On the bottom of this relay is what looks like a typical Ford 1940's resistor with the heat shield curled around the resistor and when energized the relay bypasses the resistor. There are three wires going to this device, one from the solenoid, one from the main engine harness and the other going to the ignition coil. After replacing my park brake cable I snapped off the spot welds holding the relay housing to the mount. I soldered it back on and recently when I replaced my steering gear with another I finally rebuilt grrrrrrr! I bumped it and snapped the soldered mount off again! I will repair but am looking for a replacement TomO 07-13-2019 @ 6:06 PM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 bThe purpose of the ballast resister is to regulate the current going through the coil. The 49-55 coil has a higher impedance than the earlier coils and that is used to regulate the current flow. The bypass of the external resister during starting did not appear on Ford Products until 1956. If your 1950 Mercury is a 6 volt system using the 49-53 Ford, Lincoln, Mercury coil, you do not need an external resister and can eliminate the contraption on the driver's side inner fender. If your Mercury has been converted to 12 volts, you can buy a different starter solenoid that has the ignition terminal and add a wire from the terminal to the coil terminal. Either way, you can get rid of the fender mounted relay that keeps getting in your way. Tom This message was edited by TomO on 7-13-19 @ 6:10 PM

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