good alt but no power troubleshooting

Kendrick · #1 (**permalink**) 11-06-2009, 07:14 PM

Just got a new alt tested good yet I dont get any power in the truck?! F-350 94 7.3 I checked to see if there was any resistance between the pos terminal and the alt and got .05 aka none. the plugs look to be in good shape and are seated firmly. not sure what else to check on it.

Dave Sponaugle · #2 (**permalink**) 11-06-2009, 10:05 PM

No power in the cab?

wreckinball · #3 (**permalink**) 11-07-2009, 12:08 AM

on the voltage regulators wiring connector, there are three to four pins that make up a solid piece. This piece is black usually and snaps onto the regulator. i had one loose one time and it made my truck die and not charge at all. Or it could be a bad regulator. Or it could be you have the wired backwards on the alternator. Lots more but reply and let us know.

Kendrick · #4 (**permalink**) 11-07-2009, 12:48 AM

I have the built in reg with 3 pins in 1 group and a wire that goes from the middle pin to a single pin on its own Ford E-Series E Series 7.3L Diesel 1992 Alternator 7756:eBay Motors (item 330371989091 end time Nov-26-09 11:20:44 PST) has the same type of terminals mine has. in that pic left hand has a nut for main power out. right has the gray 3 prong and inbetween is a small square terminal that goes from the middle gray terminal. I have no idea where those 3 wires from the alt run. I have not verified that the pins in the connector are good but have wiggled wires to make sure they were not broken.

Kendrick · #5 (**permalink**) 11-07-2009, 11:19 AM

I just checked the terminals and I get a good connection between the yellow wire and the positive terminal. It ties in with the alternators main cable at the starter silinoid where it also connects to the pos terminal of the battery. I checked the middle prong to single connector and that also was good. I then checked the green/brown wire to the wire harness and it to had a good connection. The only wire I have no idea where it ends up is the green brown. any suggestions?

Kendrick · #6 (**permalink**) 11-08-2009, 06:35 PM

Does any one have a good wiring diagram or know where the green W brown strip wire for the alt goes? The criton? breakdown is pretty crappy doesnt show alt or battery in most of their diagrams.

Dave Sponaugle · #7 (**permalink**) 11-08-2009, 09:06 PM

Closest thing I see is light green with red stripe going to the charge indicator if you have the internaly regulated alternator.

That wire would have voltage going to the alternator when the key was on, backfeeding through the light/gauge.

Looking at that picture, with the output bolt being left and moving to the right.
Bolt has Black/orange wire going to starter relay/positive battery post.
Next wire is white/black stator terminal goes in a short loop to the first position on connector 2 which is the regulator S terminal.
Second wire in that connector is yellow/white on the A terminal which also goes tot eh starter relay positive terminal.
Third wire on the I terminal shows light green/red going to the charge indicator in the insturment cluster.

Insturment cluster shows a light and resistor hooked to terminals B11 and B12, B11 is light green/red going to alternator
B12 is red/green from the ignition switch

Just saw this link with better pictures a couple posts up.

From the looks of this link you only have two wires going out to the chassis wiring.

The big wire to the starter relay and the green/red wire to the charge indicator.
They put the yellow/white wire right on the battery output terminal, which makes sense since that is where it goes electrically.

http://www.fordfuelinjection.com/?p=75

So if the charge indicator bulb is burnt out, you may not be getting enough current to the regulator for the alternator to start charging.

Kendrick · #8 (**permalink**) 11-08-2009, 11:34 PM

not sure what to say. the new alt was tested good at the store. I can try manually routing all the wires around the harness to make sure it isnt somthing stupid in the conectors. the battery meter does move properly when the system is turned on. it will got to just above 8v when the glow plugs are on up to just under n and then pulse as the emmisions burst from the GP's are switched on and off.

The only thing that I see problematic would be the connector to the alt fromt the red/black wire looks to be a replacement that is not properly sized. I have it making decent contact but would that make any difference to whether the alt would put out current? Also I noticed a mark that said to ground here to test alt. does that mean put the black lead to that screw and the pos to the charging stud? or does that mean put a wire from that point to the chasis for ground?

I have tested voltage from the post that the connector goes to not the connector and no voltage. Its possible that the "first position on connector 2 which is the regulator S terminal" might not be making good connection would that cuase the reg to not put voltage out?

Also that pic is for similer to mine but not the exact one. I couldent find a good pic of my model. The only difference externally is the mounts though.

The yellow wire in mine goes all the way back to the pos terminal area rather then directly to the pos post on the alt like that pic.

Dave Sponaugle · #9 (**permalink**) 11-08-2009, 11:58 PM

From what I have read about the 3G alternators, with the key on you should have power from the truck to the voltage regulator on the green/red wire.

If there is no voltage there, the alternator does not get excited and will not charge.
According to the diagrams I have, it is backfed through a light in the dash.

Do you ever see an alternator light somewhere in the insturment cluster when you turn the key on?
How about when the engine is running?

All of my normally off warning lights self test when you first turn the key on.
I would assume the 94 does the same thing.

Maybe someone with a 93 or 94 can say where that light should be.

As for the yellow/white wire, I can see Ford running it all the way over to the starter relay even though it only needs to go to the alternator output.
The factories have a way of making wiring harnesses much more complicated than they need to be.

Kendrick · #10 (**permalink**) 11-09-2009, 06:16 PM

that would explain a lot then. I just recently changed the dash out to a factory original. at that time I started having the issues. I dont know I suspect some of the bulbs are burned out will have to check and see with that. I never noticed a battery "light" but i was watching the volt meter, just checked the old console and there is a battery light. thats the best news I have heard in a long time for this truck lol...

now I just have to fix the fuel pump so I can try out your suggestion. either the fuse or the moter died.