Distributor Swap Question
Thread Starter
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Freshman User
Joined: Jan 2002
Posts: 31
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From: San Luis Obispo
Distributor Swap Question
Hello Everyone,
Today I received a new Mallory Unilite Distributor. I have already set it in the truck, but I'm having trouble with the wiring. The new distributor has these wires:
Red: + Coil
Green: - Coil
Brown: Ground
The original distributor harness has a yellow/brown, blue/brown and green/black wires.
I was hoping someone could help me figure out which wires to connect. I appreciate the help.
-Matt
'77 F-250 351M
I also posted this topic under 73-79 trucks...wasnt sure where to place it
Today I received a new Mallory Unilite Distributor. I have already set it in the truck, but I'm having trouble with the wiring. The new distributor has these wires:
Red: + Coil
Green: - Coil
Brown: Ground
The original distributor harness has a yellow/brown, blue/brown and green/black wires.
I was hoping someone could help me figure out which wires to connect. I appreciate the help.
-Matt
'77 F-250 351M
I also posted this topic under 73-79 trucks...wasnt sure where to place it
Posting Guru
Joined: Aug 2000
Posts: 1,984
Likes: 2
Matt, you don't connect anything from the original harness. Like you said, the red wire to coil positive, green to coil negative, and the brown can be grounded anywhere on the engine. DO NOT cross the red and the green! It will destroy the module if you do.
The original distributor harness is not used and can be removed along with the DuraSpark module, or you can leave it in place; your choice.....
The original distributor harness is not used and can be removed along with the DuraSpark module, or you can leave it in place; your choice.....
Posting Guru
Joined: Aug 2000
Posts: 1,984
Likes: 2
What BearTracks says is true. The coil positive wire is a switched wire, and it is resisted if the coil resistor wire is still intact. If I remember correctly, the Mallory module will work in the voltage range of 6-18v. If it's wired to the coil positive terminal, the running voltage will be about 9-11v, which is well within the Mallory's voltage range.
I had a Mallory Unilite in a Bronco II, and used two resistors in series to power it. This dropped the voltage down to about 7-8v when running, and it ran fine.
If you're concerned about powering it from the coil wire, you can splice into the red wire going to the DuraSpark ignition module. This is switched 12v power. You'll also need to wire a resistor in before the distributor, however. If the instructions say to wire it to the coil positive terminal, that's what I'd do.....
I had a Mallory Unilite in a Bronco II, and used two resistors in series to power it. This dropped the voltage down to about 7-8v when running, and it ran fine.
If you're concerned about powering it from the coil wire, you can splice into the red wire going to the DuraSpark ignition module. This is switched 12v power. You'll also need to wire a resistor in before the distributor, however. If the instructions say to wire it to the coil positive terminal, that's what I'd do.....
Thread Starter
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Freshman User
Joined: Jan 2002
Posts: 31
Likes: 0
From: San Luis Obispo
Ok, So here’s the scoop. I cut the red wire running to the duraspark module and ran it to the coil. I spliced this wire and the red distributor wire together on one side of a 1.3-Ohm resistor. The other side of the resistor was run to the + side of the coil. When I attempted to start the truck, it backfired once and then smoke began coming off the resistor. 
When I turned the ignition off the smoke stopped. Any advice would be greatly appreciated.
Thanks
-Matt
When I turned the ignition off the smoke stopped. Any advice would be greatly appreciated.Thanks
-Matt
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Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
The resistor must be of sufficient wattage to carry the power. The voltage across a saturated coil will be 6 volts. That means the voltage across the resistor is also 6 (or more) volts.
Power = E x E / R
Power = 6 x 6 / 1.3 = 27.7 Watts
You should use at least a 50 Watt resistor, or better a 100 watt resistor.
The correct method for wiring the Mallory Unilite is Red wire to coil (+). Green wire to coil (-). Brown wire to ground.
The coil (+) is also connected to switched 12V through a resistor of sufficient wattage to handle the 27 watts. The factory resistor wire is made for this. You should use the factory resistor wire.
Power = E x E / R
Power = 6 x 6 / 1.3 = 27.7 Watts
You should use at least a 50 Watt resistor, or better a 100 watt resistor.
The correct method for wiring the Mallory Unilite is Red wire to coil (+). Green wire to coil (-). Brown wire to ground.
The coil (+) is also connected to switched 12V through a resistor of sufficient wattage to handle the 27 watts. The factory resistor wire is made for this. You should use the factory resistor wire.
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