7.3 IDI charging problems

[rustygold]

Do check the battery light on dash if it does not illuminate with key on engine off then you need to change the bulb or repair wiring.

Hey guys i am having the same problem as the op and need help i have the VR grounded good(brand new) and have ran a wire strait from the b+ post on the alt strait to the battery. Nothing changed. The A terminal reads 12.6 on the VR. Im stuck brand new batterys. Fresh VR. newer alternator. And i have cleaned most of the connections....

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[Cubey]

Is the nylon(?) 2 pin connector that plugs into the alternator making good contact? My RV's retainer clip part is so weak that it doesn't clip in tight to the alternator anymore. If it wiggles loose, it results in the alternator output not working until I reseat it.

 

[Buffetkiller]

I can put 12v to the f wire coming out of the VR and the alternator charges but if not it doesent. The VR is getting power from the yellow wire but not sending it.... what does the white and black wire do coming out of the ALT?

 

[franklin2]

I can put 12v to the f wire coming out of the VR and the alternator charges but if not it doesent. The VR is getting power from the yellow wire but not sending it.... what does the white and black wire do coming out of the ALT?

Did you say what year truck you have? On some trucks, the white/black goes to the "S" of the regulator. Did you check the dash light like the other poster mentioned? That is very important for it to operate correctly.

 

[Thewespaul]

If it’s an obs this is for you.

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[Buffetkiller]

Did you say what year truck you have? On some trucks, the white/black goes to the "S" of the regulator. Did you check the dash light like the other poster mentioned? That is very important for it to operate correctly.

Its an 87. Does that mean its an obs? And no when my key is on the battery light does not illuminate. I didnt know about that issue. What does that light have to do with the alt?

 

[franklin2]

Its an 87. Does that mean its an obs? And no when my key is on the battery light does not illuminate. I didnt know about that issue. What does that light have to do with the alt?

I am going to assume you have the older style with the external regulator. The diagram above is for the internal regulator style.

The light in the dash is important. It is what triggers the regulator to bring the alternator online to charge when you turn the key on. This keeps from running the battery down when the key is off. Without this signal, the alternator will not be brought online to charge.

To verify you are not getting a signal to charge, take your meter or testlight and probe the "I" terminal on the regulator. When you turn the key to run, you should get voltage on the "I" terminal. Here's a diagram of a 85, which is very much like your 87 if you have a external regulator.

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[franklin2]

The lightgreen/red is the trigger wire. The software shrunk the picture, it's hard to see. Here's a raw link to it.

http://www.garysgaragemahal.com/charge--power-distribution-diesel.html

If you go to the link, and go down to page 24, you will see the red/lightgreen goes to the keyswitch. On this particular truck in 1985, it did not use a light. It seems Ford changed things around from year to year, my 89 has the external regulator type charging system and it uses the light.

 

[Buffetkiller]

Ok so the light circuit is the vrs trigger wire basically. Cool i will look at that cause its deffinetly not turning on. Thanks guys if i have more problems ill get back to you. Thanks for the diagram franklin!

 

[IDIBRONCO]

Its an 87. Does that mean its an obs?

FYI, 1987 was the first year of the Brick Nose.

 

[Buffetkiller]

Ok having some issues still... the light does work when i make it work with my power probe. The green and purple wire coming from the dash to the I terminal on the VR is getting 12v when the truck is on. The light will not turn on when the key is cycled. My question.... does the light absolutly have to work even if the I terminal has power to it? Any advice would be appreciated.

 

[Reggie f250]

If the other wiring to regulater is good the regulater is bad.

 

[franklin2]

Ok having some issues still... the light does work when i make it work with my power probe. The green and purple wire coming from the dash to the I terminal on the VR is getting 12v when the truck is on. The light will not turn on when the key is cycled. My question.... does the light absolutly have to work even if the I terminal has power to it? Any advice would be appreciated.

Get the truck running. Probe the regulator terminals with it running.

You should have 12v on the I terminal. Like was said, this will bring the system online to charge.

You should have 12v on the A terminal. This is the sensing wire for the regulator, it tells it what the voltage level is in the trucks wiring.

S may have 7v on it, or it may not even be hooked up. It is usually going directly to the S on the alternator.

The F terminal should have something on it. The F is how the regulator controls the alternator. As you found out, if you put 12v on the F of the alternator, it throws the alternator to wide open and is a good test to see if the alternator is good. When things are working correctly, the voltage on the F will vary as the electrical needs of the truck varies, which it knows by looking at the A terminal.

If you have voltages on all the terminals except the F, and the regulator body has a good ground, I think the regulator is bad. If it's bad, double check the F wire leaving the regulator and going to the alternator. Unwrap the harness if you have to. I do know if this F wire is accidentally grounded out with the engine running, it will fry the regulator in short order. So make sure it's not rubbing the engine block somewhere.

 

[Buffetkiller]

Super detailed thankyou