Ignition system resistor?
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Ignition system resistor?
I'm installing a 302 from a 72 torino into a 54 f100 and I'm having problems with the ignition system. I've wired the ignition so that it gets 12 volts at start up and wired in a ballast resistor to drop the voltage while running. The problem is the resistor starts to smoke when the key is on for a minute. The resistor drops the voltage down to 6 volts when everything is hooked up. Anybody have any ideas? This should be a simple install but I'm not sure why the resistor is smoking.
Lead Driver
Joined: Oct 1999
Posts: 6,777
Likes: 553
From: Kalispell, MT
They do get hot. Maybe just a defective one? You have it wired in the between the ignition switch run post and the coil? What type of resistor are you using? Mounted on the firewall where nothing else gets hot? I get the ceramic body rectangular ones. I just tell the counter guy I want one for a 71 Chrysler.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
What type of resistor are you using?
From my note files:
Conventional Point type ignition systems:
============================================
These specs are for a 1959-1974 systems.
Specs for Ford conventional point type system:
All resistance measurements at 75°F
Primary resistance..... 1.40 - 1.54 Ohms
Secondary resistance..... 7600 - 8800 Ohms
Amp draw engine stopped..... 4.5 A
Amp draw engine idling..... 2.5 A
Primary resistor..... 1.30 -1.40 Ohms
Mopar or Chrysler dual resistor units have two resistors and 4 connection tabs.
One resistor is 5 ohms. The other resistor is 0.5 ohms.
Use two 0.5 ohm resistor units in series to approximate the Ford primary
resistor value The rest of the resistance will come from the wires and
connections.
The connections to the ceramic resistor should NOT be made with standard
crimp on wire terminals. Go to an appliance parts store and get the crimp on
wire connectors made for heater terminals in an electric dryer. These terminals
are made of a special alloy that will work with the effects of high temperatures
without corroding or losing their crimp/connection pressure. These connectors
are a good thing to use on the blower motor resistor module used for the heater
blower motor speed control connections also.
From my note files:
Conventional Point type ignition systems:
============================================
These specs are for a 1959-1974 systems.
Specs for Ford conventional point type system:
All resistance measurements at 75°F
Primary resistance..... 1.40 - 1.54 Ohms
Secondary resistance..... 7600 - 8800 Ohms
Amp draw engine stopped..... 4.5 A
Amp draw engine idling..... 2.5 A
Primary resistor..... 1.30 -1.40 Ohms
Mopar or Chrysler dual resistor units have two resistors and 4 connection tabs.
One resistor is 5 ohms. The other resistor is 0.5 ohms.
Use two 0.5 ohm resistor units in series to approximate the Ford primary
resistor value The rest of the resistance will come from the wires and
connections.
The connections to the ceramic resistor should NOT be made with standard
crimp on wire terminals. Go to an appliance parts store and get the crimp on
wire connectors made for heater terminals in an electric dryer. These terminals
are made of a special alloy that will work with the effects of high temperatures
without corroding or losing their crimp/connection pressure. These connectors
are a good thing to use on the blower motor resistor module used for the heater
blower motor speed control connections also.
Fleet Owner
Joined: Jul 2004
Posts: 27,297
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From: NM
I'm using a single-wire Chrysler resistor (Niehoff AL-125C) mounted on a bolt to the firewall, with a couple washers behind it to let air circulate around it. It smoked for the first 5 minutes, appears to be the binders in the insulation the nichrome wire is wrapped around.
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New User
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Originally Posted by Torque1st
You need two wired in series or the ignition will draw too much current and overheat. Make sure you get the right resistance.
If you run two resistors in series wont this drop the voltage too much?
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Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Some smoke might be normal the first few times you run it. These things get very hot and if there are any oils or other residue on it from handling it will smoke until those have burned off. After that it should be okay... 
Last edited by GreatNorthWoods; Sep 3, 2006 at 01:55 PM.
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Fleet Owner
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From: NM
Originally Posted by ftech
If you run two resistors in series wont this drop the voltage too much?
From your description, I'm not sure you have any problem, really. If it keeps smoking, then I'd check further. 6v measured at the coil after the key has been on for a short time actually seems a little low but it depends what coil you're using. Make sure the Torino coil is not an internal resistor type (IIRC they used a resistor wire, not a ballast resistor). I'm thinking most 12v external ballast coils expect around 7.5 - 8 v under these conditions.
Last edited by ALBUQ F-1; Sep 3, 2006 at 03:22 PM.
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Joined: Aug 2006
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Definite answer: Go with a modern electronic ignition that does not require a resistor.
If you're concerned about your motor looking original, keep your stock ignition in your garage, and install a high performance electronic ignition in your motor so that you can enjoy improved performance.
If you're concerned about your motor looking original, keep your stock ignition in your garage, and install a high performance electronic ignition in your motor so that you can enjoy improved performance.
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New User
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Originally Posted by bob s jr
are you running one or to power wires to your coil. are you running a seperate 12v source from your ignition for your start. and running a secong through the resistor.
Fleet Mechanic
Joined: Jun 2004
Posts: 1,784
Likes: 45
From: Minnesota
Buy a 12 volt pertronix ignition I put one in my truck and it went from cranking for 3 or 4 seconds with the choke to start to starting with the press of the button with no choke. The ignition just replaces the points so you don't have to worry about burning them up.
Fleet Owner
Joined: Jul 2004
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From: NM
Originally Posted by ftech
I'm running one wire to the coil. The start side is spliced in at the positive wire at the resistor. Then the other side of the resistor is to the ignition.
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New User
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Originally Posted by ALBUQ F-1
Is that direct 12v power for starting coming from a 4-post Ford starter solenoid's "I" terminal? If so, you're OK. If you are using a different solenoid (like an original 3-terminal) or wired from the starter terminal on the ignition switch, you will back-feed the starting side of the circuit, including the starter solenoid coil. That would increase the draw thru the ballast and could be why you're seeing smoke. This is how it should be done.