I been working on 02 F250 4x4,7.3, manual T-case that quite charging. We put in new batteries, had alternator tested, cleaned the cables and still no charge.
Checked for chaffed wires, taped up some that were getting nearly rubbed thru. Finally installed new alternator, still no charge.

I 've spent quit a few hours today sifting through the threads on here dealing with NO CHARGE conditions. I have 12v at the green/red wire on the alternator that turns on the regulator. But when I use my test light on this wire it barely lights the bulb. So I started traceing the wire back towards the cab up to the instrument cluster. Ford told me the GEM on this truck was inside the intrument cluster. ( I'm not sure if the GEM has anything to do with chargeing)
Where the wire comes out of the cluster and i assume directly from the volt guage, it reads 12v but barely lights my test light bulb.

So I am thinking there is a problem with the cluster. I'd like to ask anyone if they have dealt with this before and know if the cluster can be repaired or if I need an entire cluster.

One other thing, I used a jumper wire from the battery to the Green/Red wire at the alternator and got the alternator to start produceing 13.5-14 volts.

Also. previous to this NO Charge condition the battery volt light would flicker on and off.

Thanks in advance for your help.

Pete

 

You have a bad alternator. It may be putting out 13V but it has no ampreage behind it so it is a very weak 13v. replace alternator with a NEW unit, (not rebuilt) and I bet your problems go away.

 

I'm probably just not reading this right, but is the question having to do with the guages showing a charge or is there actually no charge at the batteries? What is the voltage at the batteries? I understand the preceeding comment about voltage, but little or no amperage and agree that is a possibility. I am just trying to clarify, for myself I guess, the exact nature of the question.

Steve

 

No charge at battery. The voltage at the batteries is 12.5v. I'm using a Volt meter to test. Last night when I ran the jumper wire from the battery to the Green/Red wire on the alternator it started chargeing. I think there is plenty of amperage. The alternator heated up quite a bit when I got it to start charging, the voltage in the battery had been getting low from my testing procedure.

 

So, you essentially ran a second wire to charge the batteries and everything started working. If you did nothing else, had over 13 volts at the batteries, and did in fact have ample amperage, it has to be a connection issue as you did nothing other than establish a better connection. At least that's my thought at this point.

The kicker, as suggested previously, is you can have voltage, but very little amperage. Most folks do not have a meter that is capable of testing amperage and that makes it really tough to troubleshoot. What do you think about running by Advance or similar and asking them to check the alternator?

I'm not sure what more to suggest at this point,

Steve

 

I have a pdf of the starting/charging wiring diagram for the single alternator setup but I have no idea how or if I can post it, so I'll try to describe what I see.

The B+ (12V) Blk/Org wire goes to a fusible link and the glow plug relay.

The "A" terminal on the alternator (Org/Lt Blu) wire goes to fuse #6 in the power distribution box.

The "I" terminal on the alternator (Lt Grn/Red) wire goes to the charge light in the dash which is in parallel with a 470 Ohm resistor. From the charge indicator light that wire becomes a Wht/Yel wire to fuse #29 in the Junction Box/Fuse/Relay Panel. From fuse #29, the wire goes to the ignition switch but now it's a Red/Blk wire. The ignition switch completes the circuit only in the Run/Start positions and when it does complete the circuit, it does so via a Lt Grn/Ppl wire to fuse #20 in the Power Distribution Box.

Hope you can make sense of this enough to draw out your own wiring diagram. Good luck!

 

I forgot.. The point is that the GEM does not appear to be directly involved with the charging circuit.

 

That piece That I put in Bold above sounds alot like how my 95 Mustang was set up. I spent Months trying to find out why I finally got a Schematic and saw that. I pulled my insturment cluster out and found out why some of my gauges had died. there was two connections plugs on the back as soon as i plugged it in alternator started throwing out 14v it charged.


Does your battery light come on? If not and it is not charging I would look there you might of just had connection come loose on the insturment panel on the back.

 

That 470 ohm resistor explains why the LtGrn/Red wire at "I" Terminal barely lights my test light.

I got another alternator yesterday and now everything is working properly.

Thank You all for the help.