Is anyone familiar with what the Ignition Control Module does on a 1975 F250? I am rewiring the entire truck and almost everything is done except the ignition. What is holding me up is the ICM. I feel like it will be easier to figure out if I know what it actually does for the truck.
Thanks!

 

it receives pulses from the module in the distributor which in turn opens the primary coil circuit causing it to fire whichever plug is aligned with the rotor...in some applications the timing is retarded during cranking.

 

The DuraSpark ignition module used in 1975...is 1975 only.

 

What he said and a little more for ya.

Ignition modules, 74 (black grommet) and 75 (green grommet) are year specific and will not interchange. 76 to 79 (blue grommet) are interchangeable. Ignition modules: 1974 is 1974 ONLY / 1975 is 1975 ONLY.
Blue module introduced in 1976 was used well into the 1990's. D4AZ-12A199-C 1974 only.

DuraSpark ignition modules identified by a colored plastic insert located above where the wires feed out.
2 others: One has a red plastic insert, the other has a yellow or brown plastic insert.
Red module is D7AZ-12A199-A used in some CA vehicles ONLY.
D9AZ-12A199-C (replaced D8AZ-12A199-A). One of these modules is yellow , one is brown .. Since the part number was replaced, I (he) cannot recall which module was which color.

These modules were used in 1978/79 302 & 351M/W vehicles sold in high altitudes only.
351W: Passenger Cars & Econolines only.
1U2Z-12A199-AA (replaced D6AZ-12A199-B - D7AZ-12A199-B - D8VZ-12A199-A - D9VZ-12A199-A) .. Ignition Module - blue insert (Motorcraft DY-893) / Available from Ford.
Myriad 1976/90's FoMoCo vehicles.

Green Sales in OH.
Collectors Auto Supply in WA.
Haven Ford in KS.
Klimesh Motor Sales in IA.
Bob Allen Ford in KS.
Freese Motor Inc in IA.
Wesley Obsolete Parts in KY.
Dennis Carpenter Ford in NC.

 

awesome thanks for the info! Do you happen to know what is unique about the 1975 green module?

 

Resurrecting this thread from the dead, because it is the exact question I have.

I'm rewiring my 75 f250 completely. It had the black ICM. Since I'm rewiring, it will be easier to find replacement blue ICM. What needs to be wired differently from the 1975 icm?

 

I don't know that you as the user, can rewire the blue grommet ones to use in a pre '76 application without a lot of other changes.

 

What's different about the earlier systems that they don't interchange? Is it physical, like different plugs, or is it internal circuitry that won't run on other years? And if it's internal, what needs to be matched to the ICM to make it work? I'd think with these being relatively dumb electronics, it just reads a pickup signal and triggers the coil, if it's just the plugs being different, splicing any ICM in as long as it's getting inputs in the ranges it needs it should work, no?

 

I don't want to rewire the blue ICM. I want to rewire my truck so it accepts the blue ECM, as those are much easier to source in the future. I am doing a complete rewire of the entire truck.

 

I don't have them for the '74 or '75 versions, but this is what I kept because mine is a '77. Might be different pick ups, etc or coil? It's maybe a start.

 

found this:

https://cb4x4.com/thread-3215.html

Black is '74
Green is '75
Blue is '76-on

They don't mix and match because the harness is different for each type.

1974 SSI – Black insulator, 7 wires, Napa # MPE TP35SB
1975 SSI – Green insulator, 7 wires, Napa # MPE TP36SB
Duraspark II – Blue insulator, 6 wires, Napa # MPE TP40SBAttached Files Image(s)

 

Yeah, that was the other two, '74 and '75 I didn't have. Maybe it is just a matter of "re-wiring", but I see different resistance values of 1.1 and 1.4 ohms on the ballast?

So, if the same coil, 1.1 ohm would cause a hotter spark than a 1.4 ohm ballast ... would it not ... or is it a misprint?

Other than that, I see just 6 wires on the 'blue ones, but looks like some of the others used 7 initially?

I think OP is rewiring?

 

I believe there are slight differences between the way the modules operate. Different tests in the shop manuals for the respective years. The blue modules sense engine not turning, and it shuts down and waits for a input if the key is left on, I think the other 2 just stay on with key. I could have it mixed up and a long time since the 70's.

 

I also found this PDF link to what looks like the 76+ Ford Duraspark troubleshooting manual which describes how the system works, might be some help.

https://www.pittauto.com/customer/pi...20Ignition.pdf

 

Thank you tbear and speedfreak. Looks like I'll just wire up for v the 76+ blue ICM.
it is interesting that my 75 has a black module not a green one.