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different cab wiring help

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Old Apr 24, 2015 | 06:58 PM
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different cab wiring help

I have a truck i just got with a 1974? f150 frame and 300 inline 6 manual 4 speed with granny gear (PO said non-ac)

It now has a 1978 f350 v8 auto cab with a/c.

The wiring is a little mixed between the 2 and i'm not sure if i can decifer colors/tracers anymore.

It needs a new battery and some fused link wiring
I know it needs an ignition module.
I have a few rebuilt 3g alternators i'm looking to put one on.

Is there anything not compatible? If i follow one wiring diagram or the other will i fry something?

I know i'm an arm chair mechanic right now, but i want some do's and don'ts before i ruin the truck. thanks in advance
 
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Old Apr 24, 2015 | 07:48 PM
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Originally Posted by dentsidejay
I know it needs an ignition module.
Is there anything not compatible?

The '74 and '78 modules don't interchange. '74 was a one year only version.
It's easy to tell which you have. Look at the plastic grommet that surrounds the wiring where it enters the ignition module, if its blue, you have the module for the '78.
That's how the modules are identified, by the color of the grommet. The blue is the best and most common.
I can't remember off hand but I think the '74 grommet is black.
 
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Old Apr 24, 2015 | 08:54 PM
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I'll check on that tomorrow, thanks.
 
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Old Apr 24, 2015 | 09:05 PM
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Originally Posted by mikeo0o0o0
The '74 and '78 modules don't interchange. '74 was a one year only version.
It's easy to tell which you have. Look at the plastic grommet that surrounds the wiring where it enters the ignition module, if its blue, you have the module for the '78.
That's how the modules are identified, by the color of the grommet. The blue is the best and most common.
Why is the blue one the best??? I have an off road vehicle that has no top end. It is running really bad right now. I am not sure if it is fuel or ignition related. It is running the blue module. Was thinking of replacing it or tearing down the carb. Which should probably be done anyway. Last year it was getting rough and now it is really bad.
 
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Old Apr 24, 2015 | 09:31 PM
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Originally Posted by Brian Ski 44
Why is the blue one the best??? I have an off road vehicle that has no top end. It is running really bad right now. I am not sure if it is fuel or ignition related. It is running the blue module. Was thinking of replacing it or tearing down the carb. Which should probably be done anyway. Last year it was getting rough and now it is really bad.
By the time Ford started using the blue grommet version they had pretty much gotten most of the bugs worked out. The '74 and '75 each use their own module and neither interchanges with any other module. The blue version came out in '76 and was use, as I recall, into the mid nineties on certain applications.
If you do replace it, spring for the extra money and get either genuine Ford or genuine Motorcraft. The cheaper imports have a very high failure rate.
 
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