Hi all, glad to see forums are still alive and active. It’s been years since I’ve posted on one, but I’m stumped with this issue and desperately need some help. I’ve spent days searching forum posts and googling and trying different things with no avail.



Vehicle: new to me 2001 F250 Superduty 7.3, 250k mi, single alternator, no ambulance package.



Issue: today is Friday. truck doesn’t start last Friday. Jump truck and notice volt gauge on cluster going down. Assume alternator, swap alternator with autozone reman alternator, no luck. Swap with motorcraft reman alternator, no luck. Chase wires like fusible link, alternator plug wires, starter solenoid wires, grounds, No luck. Swap batteries, works! 14.4v while running, Hooray.



Truck is running fine through the week until Thursday. Driving around and notice volt gauge dropping again. Check volts while running, 10.4v. Assume alternator or voltage regulator, swap alternator, no luck.



Additional important details: both batteries read 12.4 Volts when charged and placed back in truck. B- to alternator post reads 12.4v. UNPLUGGED Alternator plug orange wire reads 12v KOEO, 12v KIEO, and 12v engine running. Green plug reads 0v KOEO, 4-5v KIEO and with engine running. PLUGGED IN alternator plug orange wire is the same, but nothing from green wire through all scenarios. Today I realized I NEVER have seen the battery light, so I have gotten so far as to pulling the cluster out and putting in a new bulb, to no avail.



HOWEVER, I started testing at the cluster to see if there was a break in that wire somewhere, and I found that I’m only getting 4v to the battery light, but all other lights get 12v. Very odd



WHERE IM AT NOW: So I decided to check the starter solenoid again. Fusible links all test 12v, but I found that grounding the cable coming from positive battery to starter solenoid only gave me 4v. I hope it’s in relationship to the bulb. Cleaned up posts, currently charging batteries, going to give it a go tomorrow.



In the meantime, does anyone have any additional ideas?

Thanks in advance yall.

edit: just had a thought, could 4v at battery bulb be because of GPR draw when key is in? Tomorrow I’ll try to read it for a couple of minutes to see if voltage changes.

 

Fix the issue with the low voltage at the charge indicator light in the cluster and you'll probably fix the charging issue. If that indicator circuit cannot supply full battery voltage potential to the generator's "I" input, the thing won't work (no charge).

Check fuse F29 in the underdash fusebox and verify with a meter or test lamp that it is supplying full battery voltage when the ignition switch is in START or RUN. Could be a blown fuse but, more likely is loose or corroded in its socket causing an intermittent connection or there is something else in the circuit that's making poor/no connection, perhaps from the ignition switch.

 

Thank you for the response projectSHO.

So I cleaned up the post I found last night a little bit. Getting 12v to it now. Interestingly enough, Fuse 29 gets 12.1v, and the fuses on the other side, 1-11, get 12.2-3v. Airbag light turns on(same fuse), so it tells me the fuse is good. It’s specifically the charging circuit I think.

Still no battery light with KIEO, but alternator now gets power, albeit 10-11 volts. I think I didn’t clean the grounds/starter solenoid enough.

I’m going to clean up battery posts and check grounds again.

Thanks all. Hope you’re having a good weekend.

 

What are you referring to as "KIEO"? Key On, Engine Off is known as KOEO in Ford-speak.

With the I lead disconnected from the alternator and the ignition switch in RUN, you should measure battery voltage on that lead. Briefly ground it and the CHARGE/BATTERY light in the cluster *should* light up. If these two tests fail, then the charging portion of the F29 circuit has a fault. Focus on making sure it works before doing anything else significant.'

Sounds like you have the schematic, yes?

 

Sorry, I mean key in engine off. I didn’t want to confuse KOEO with KeyOutEngineOff, so I went with KeyInEngineOff. But either way, yea, key in on position, engine off.

let me give that a shot.

just to clarify, you’re saying unplug alternator and put pos lead of multimeter to green/red slot on plug, and neg lead of multimeter to ground, correct? I think I’ve checked this and with key on, I’m getting 3-4v. I haven’t checked to see if battery light comes on when I do this.

sorry if I am misunderstanding. Thank you for explaining.

I am using this schematic.

 

Yes, check the LG/RD wire with it disconnected from the regulator and ignition switch in RUN (KOEO). Should read full battery voltage if the full F29 circuit is intact.

If you read 3-4 volts, follow up on my previous instructions to check at F29.

That's the correct schematic for the charging circuit but there are a couple of others that may get called into play, depending on what your readings are from the above test.

 

Well now I’ve really dug myself in. Went to clean up fusible links and other starter solenoid wires so I’m SURE they’re clean, go to tighten, snap solenoid post. Go to remove nut from snapped post, break battery cable. Also notice fusible link is breaking. Pictures below.

snapped solenoid post


broken battery cable


Fusible link breaking



Kick it while it’s down I guess.

Ford is closed tomorrow. Anything I can find at autozone, Napa, oreillys or the like to splice/replace these bits?

 

Couple of points:

1. It sounds like you're referring to the firewall-mounted component as a "solenoid". That component is correctly called the "starter relay". The starter solenoid is mounted on the starter motor. Replacement starter relays should be available at any auto parts store. Be aware that many auto parts stores and parts counter drones use the wrong terminology.

2. The molded battery and starter cable can be replaced with separate cables available off the rack at just about any auto parts store. Just take the old one out and match up gauges, length, and terminals as needed.

3. The ring terminal on the fusible link can be replaced with a new ring terminal. Just cut the old one off, strip insulation, and install the new ring terminal.

4. When you put it all back together, make sure you put everything back on the correct terminals of the starter relay.

 

Lordy, ok. Starter relay and cables all back together. Truck starts. Thank you greatly for your help on that one. I really thought I done myself in at that point.

Now back to square one.

KOEO, grounding circuit I gives no battery light.

With truck running, Circuit I only gets 5.24v when unplugged from alternator and grounded.

Plugged in, gets nothing.

What would cause this?

edit: I don’t think it’s within the circuit, but I did just replace blower motor and resistor. Had to splice in new resistor wires because the old connector was so rotten, but I followed the wire colors and made sure they connected properly. Would this have anything to do with it?

 

Did you go check F29 and verify it's HOT IN START/RUN as previously advised and is passing power?

 

Yeah

Fuse 29 gets 12.1v, and the fuses on the other side, 1-11, get 12.2-3v. Airbag light turns on(same fuse), so I’m assuming that means the fuse is good?

 

Ignore the other fuses. I doubt the blower resistor repair is an issue unless a mistake was made.

Focus ONLY on the circuit through F29 to the instrument cluster CHARGE/BATTERY bulb to the generator connection. You're losing that circuit somewhere along the way and that is what you need to find. Since the airbag light does light up, the fault is likely beyond the junction where the circuit branches to the AIRBAG light.

Where were you measuring that? If anywhere "downstream" from the bulb, you should have measured 0 volts singe its supposed to be grounded. Don't measure on the generator's terminal with the wire disconnected, focus on the wire side.

 

Ok. Any idea where I can found a schematic or diagram for the route those wires take?

Yeah this was with the terminal disconnected. I’ll check connected today.

edit: this is where we are looking now, correct? (Red circle)


doesn’t look like it loops back anywhere, so after the indicator, where would I follow the wires? Or am I not understanding this correctly?

 

Nope. The older service EVTMs don't show wire harness routing. You basically have to use any connectors you can as guideposts and trace the rest out by hand. We know that it goes from the CJB to the instrument cluster on one side of the bulb. On the other side of that bulb, it goes through connectors C1049 and C138 as a LG/RD wire and then to the generator.

Let's back up a bit and logically troubleshoot the circuit. It might not be necessary to try and sort out that spaghetti (yet).

You're going to be looking for the two points between the voltage "disappears" or "drops".

1. Disconnect the I circuit lead from the generator and ground that lead.
2. Turn ignition switch to RUN.
3. Measure both test points on F29 and verify full (or mostly) battery voltage is present.
a. If both present, go to step 4.
b. If either missing, troubleshoot F29.
4. Gain access to the connectors on the back of the instrument cluster.
5. Check for feed from F29 at C250a-7, WH/YE wire.
6. Side of bulb socket that connects to previous point.
7. Other side of bulb socket. If the bulb was ON, this point and all of the following should be zero volts.
8. C250a-8 (connects to LG/RD wire that goes into the harness).

Let me know what and where it fails.

 

i have 12v all the way through c250a-8. Does that mean there’s a break somewhere along LG/RD from cluster to alternator?

edit: wow chasing those sounds like a pain. Can I just splice a wire from the back of the alternator into the green-red wire and bypass circuit 904? Essentially turn it into a one wire alternator?

edit edit: sorry for so many edits, I’m just sitting here trying to dissect this in my head, need to get this truck running. Am I understanding this correctly? Checking voltage from CJB onward is following the direction of the circuit.

If I get 12 or nearly 12v when grounding circuit 904 with alternator unplugged, wouldn’t that mean the circuit is complete, which means alternator just isn’t charging?