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1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

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  #1  
Old 04-13-2003, 10:42 PM
ghak ghak is offline
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location of ignition coil ballast resistor

i was wondering where it is and if you don't have one will the high voltage cause intermitent spark from arcing in the points?
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Old 04-14-2003, 12:04 AM
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location of ignition coil ballast resistor

The resistor is actually a section of resistive wire. Which is located, for some reason known only to Ford engineers , behind the dash inside a wire bundle.
If you do not use it I think the points and or coil life expectancy will be lowered.
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Old 04-14-2003, 01:47 AM
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location of ignition coil ballast resistor

thanks for the help. I'm still wondering if i even have the resistor wire on my rig, i check the voltage at the coil positive lead and it showed 12 volts. My truck also idles rough but all the plugs seem to be firing, so i have a theory that the high primary voltage arcs across the points when they open preventing the coil from firing. anyone have this problem before?
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Old 04-14-2003, 11:39 AM
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location of ignition coil ballast resistor

Well if you are sure you do not have it....you can go to the parts store and get a 1.05-1.15 ohm ballast resistor. Then put it in series with the coil +. That will drop the voltage down to close to the factory settings.
Of course then you will need to run a new wire from the "I" terminal of the starter to the coil +. That way you would retain the 12 volts during startup, and the resistor should give you the correct lower voltage during running. I think it is 9 volts or so.
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Old 04-14-2003, 05:47 PM
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location of ignition coil ballast resistor

Be sure to check the coil + voltage with the points closed or with a jumper wire from the coil - to ground. If the points are open you will measure +12 volts with or without a ballast or resistor wire. No current flow means no voltage drop.

If the points are arcing a lot, you probably don't have a ballast or the condenser is shot.

Barry
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Old 04-16-2003, 06:41 AM
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location of ignition coil ballast resistor

Can you test the voltage in the resistor wire if you don't have the distributor or coil in the truck yet or do you have to at least have the coil attached?
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Old 04-16-2003, 11:23 AM
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location of ignition coil ballast resistor

You need at least a coil to test it. The resistor wire and the coil primary windings are connected in series and form a voltage divider. Approximately half the supply voltage is dropped across the resistor wire and the remaining voltage is dropped across the coil primary. Use a stock coil for the test, a high-performance coil has a lower primary resistance and will throw off the voltage divider. That's why they have matching ballast resistors which are lower in resistance, to restore the divider.

Barry
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Old 04-16-2003, 04:37 PM
1968F250LWB 1968F250LWB is offline
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location of ignition coil ballast resistor

Quote:
Originally posted by inliner
Can you test the voltage in the resistor wire if you don't have the distributor or coil in the truck yet or do you have to at least have the coil attached?
You can check the resistance of the wire though.
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Old 04-16-2003, 09:29 PM
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location of ignition coil ballast resistor

I should think that, with the ign sw "on", there should be reduced voltage at the "Bat" coil wire, even if the coil isn't there? I have converted 3 Allis-Chalmers tractors fom 6V Neg Grd to 12V Pos Grd using Ford alternators, coils and regulators. I have used the "pink" resister wire and in one case (these tractors don't have a starter on the switch), I am feeding reduced voltage to the coil at ALL times and it starts just as well as the others that get 12V at "start".
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Old 04-17-2003, 02:37 AM
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location of ignition coil ballast resistor

Yeah, you would think that but with no load there really is no voltage drop, it has to follow ohms law. A cheap voltmeter typically has 20,000 ohms per volt compared to the 1.5 ohm resistor wire so it's practically not there as far as the resistor wire is concerned.

You're right, the coil doesn't really need 12 volts on start but it sure would like it on those cold mornings.

Barry
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Old 04-17-2003, 06:05 AM
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location of ignition coil ballast resistor

Thanks for the replies. Barry, thanks for the help with the alternator on my other posts. I just broke in my new motor and everything seems to be working great! Thanks again everyone.
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Old 04-17-2003, 03:16 PM
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location of ignition coil ballast resistor

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Old 04-20-2003, 08:43 AM
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location of ignition coil ballast resistor

I found the resistance wire on my '68 -- it is kind of a dark orange color with "DO NOT CUT OR SPLICE" printed on it. The start by-pass lead joins it at the connector to the engine harness (coil, water temp, and oil press). I tested it with my ohmmeter and it read 6.7. I then tested my chrysler electronic ballast resistor (a Standard RU-4) and it measured 1.4. As I am changing over to an electronic igntion (which should be 1.1 -- 1.8 ohms) I am going to by-pass the resistance wire and put the chrysler unit in.

Chris Seay
Bealeton, VA
'49 F-1s
'68 F-100
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Old 04-22-2003, 08:44 AM
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location of ignition coil ballast resistor

I remeasured the resistance wire in my '68 -- the first time I checked it I checked it THROUGH the ignition switch and came up with 6.7 ohms . . . I disconnected the ignition switch and measured JUST the wire and came up with 1.4 ohms -- the EXACT same as the chrysler unit!!! I can't believe my ignition switch has that much resistance . . . maybe time for a new one!

Chris Seay
Bealeton VA
49 F1s
68 F100
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Old 04-22-2003, 08:44 AM
 
 
 
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