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Discussion Starter #1
Currently chasing an issue i'm having with my 4r100 its not shifting into 4th gear I had some issues where it wouldn't go into 4th gear but after cruising for a few minutes I could restart the truck and have 4th, other times I wouldn't have any issues. Now i'm getting no 4th gear and it seems that it came right around the time that I replaced a broken column shift tube and lever... My OD light is also now stuck on... I checked the wires at the plug and the red/yellow is 12v as it should be but the white/green is at 12v and the brown/white is 8v

I Also recently had the trans rebuild replacing just about everything including solenoids
 

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Former Ford Trans Engr.
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You should check the wires to the OD button for damage. Checking the voltages doesn't tell me anything. Look for continuity from one end to the other, and for shorts to ground and to power.
 

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What? Voltage tells you everything. It is by far the most accurate and quickest way to check a circuit. Especially if you know how the circuit is controlled.
 

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Former Ford Trans Engr.
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Great! Tell him what's wrong.
 

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Former Ford Trans Engr.
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Voltages are good to know, but don't always tell the answer. I can't tell what's wrong from the voltages he posted, can you?

If I knew if each of the wires had continuity and if any were shorted to ground or power I could tell him how to fix the problem.
 

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Master BS'er
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No sir, not without a diagram I can't. Ya got me there. So that parts true enough Mark, I can buy that.

I was just saying voltage is really the king, and is a real time reading of not only the supply, but also the continuity and resistance. But, that's true that it tells ya nothing without a reference of some kind.
 

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Master BS'er
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What if the wires turn out to be fine? What then? Is there a way to condemn the switch or module without using voltage?

I will say that 8v sounds a little strange for an two position switch. Could be perfectly normal for this circuit, I can't answer that right now, but if it is normal, it would be uncommon for sure. It's also a little strange that all three wires have a voltage in them.
 

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Continuity is one thing .the circuits ability to carry the current is another thing . In the shop we load the circuit with a small light bulb from a lawn tractor . If it glows you know it's good . I agree with Mark , voltage is only part of the puzzle .
Cheers !


Sent from my iPhone using Tapatalk
 

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Former Ford Trans Engr.
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These circuits are very, very low current. One just provides a ground signal and the other powers a very small LED.
 

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Discussion Starter #12
Ill check continuity as I have time this week, for now i've unplugged the od harness in the column so the truck can shift into 4th
 

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Former Ford Trans Engr.
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With your symptoms it is likely that you have a short to ground. Make sure to check for that, too.
 

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