I need your help Oppo

"MasterMario - Keeper of the V8s" (mastermario)
10/30/2019 at 10:49 • Filed to: Helplopnik, Wrenching fail

My ‘93 F150 has a charging issue and I can’t figure it out. I’m at the point where I feel like I need to rewire everything just to make sure I know there are no issues with the wiring.

If only mine was this clean

Here’s what I’ve done so far. It has a new alternator (which involved breaking other parts and !!!error: Indecipherable SUB-paragraph formatting!!! for said broken parts).

I took that new alternator back to the shop and had it bench tested just to be sure. It’s fine.

The battery seems fine, it shows 12.8V when disconnected and holds a charge and still starts the truck fine. I’m taking that in today to have it checked just to make sure though.

I checked the wiring and everything seems right at least according to this diagram of the wiring that I was able to find. Red and yellow both have power, there is continuity from plug to plug on white, and green shows a slightly higher resistance than 510 ohms but doesn’t seem excessive.

The only other thing I can think of is the plugs are somehow damaged and not making contact, but they look fine and even wiggling them around while the truck is running doesn’t get the alternator to work.

Am I missing something?

Help

DISCUSSION (19)

jminer > MasterMario - Keeper of the V8s
10/30/2019 at 11:06

There are a few common causes for charging issues that are pretty easy remedies.

1. Clean corrosion off of battery terminals, on both ends

2. Cables might actually be bad

3. Fusible link between alternator and battery is burnt out

What does the voltage at the battery read while the truck is running?

Are you seeing the proper voltage output at the back of the alternator (not the battery)?

ITA97, now with more Jag @ opposite-lock.com > MasterMario - Keeper of the V8s
10/30/2019 at 11:10

Take a look at the battery cables. Even if the terminals look fine, peel back some insulation and see what you’ve actually got inside. I’ve had some trucks from that era in which the terminals and cables looked fine, but onc e I cut back some insulation they were completely corroded inside the insulation and causing a significant voltage drop.

Captain of the Enterprise > MasterMario - Keeper of the V8s
10/30/2019 at 11:18

I would try cleaning you’re terminals even if they look clean, I had my car not start because of that once. I also know a guy with an 02 F250 7.3 and he said that for his the actual battery cables are a weak point maybe check those and maybe replace them.

MasterMario - Keeper of the V8s > jminer
10/30/2019 at 11:21

1. Did that too

2. Hmm...I’ll have to take a look at them

3. I shouldn’t have any power at the alternator if that were the case, right?

Battery reads 12.3-12.4 when the truck is running. I’ll have to check if there is any output at the alternator when the truck is running.

MasterMario - Keeper of the V8s > ITA97, now with more Jag @ opposite-lock.com
10/30/2019 at 11:21

I’ll have to take a closer look at the cables

MasterMario - Keeper of the V8s > Captain of the Enterprise
10/30/2019 at 11:23

Sounds like I need to check the cables...you’re the third person to mention that one

jminer > MasterMario - Keeper of the V8s
10/30/2019 at 11:30

If the alternator is spinning it should be outputting ~14 volts out the back terminal on it. If it isn’t the alternator is bad as this truck the alternator should be internally regulated.

Have you cleaned the terminals at the starter solenoid too? I might sound like I’m repeating myself but if the alternator is good on an internally regulated one like this it is almost always a cabling issue.

Hail Mary if you can’t find the problem is to run a new link (fused) from the alternator output to the battery. It wont cost you too much and will fix the problem. I’ve done it before and it works perfectly, just make sure to manage that cable.

Michael > jminer
10/30/2019 at 11:43

It has to be spinning with a +battery reference, otherwise no field is generated

Michael > MasterMario - Keeper of the V8s
10/30/2019 at 11:44

Any paint between the mounting surface and the alternator? Gotta have the ground loop through the engine, as well as the +12 loop to the battery

MasterMario - Keeper of the V8s > Michael
10/30/2019 at 11:53

I’ll check, but it’s bare aluminum to the bare aluminum bracket to the block.

jminer > Michael
10/30/2019 at 11:58

Yeah that’s why you can’t push start a completely dead car. No permanent magnets in the alternator so it needs power to generate power.

This is something I’ve never actually had fail though, it’s possible but pretty unlikely. I suppose the plug could have gone bad and be making bad contact though.

Long_Voyager, Now With More Caravanny Goodness > MasterMario - Keeper of the V8s
10/30/2019 at 12:06

Just a heads up, I’ve had numerous alternators that tested perfectly that ended up being the issue.

It’s been 3 brand new ones so far, all of which I had bench tested when I still had issues. After digging through all the wiring, fuses, cables, I changed the alternator again just to be sure, low and behold, problem solved.

MasterMario - Keeper of the V8s > Long_Voyager, Now With More Caravanny Goodness
10/30/2019 at 12:17

How does that even work? lol

I’ll keep that in mind.

Long_Voyager, Now With More Caravanny Goodness > MasterMario - Keeper of the V8s
10/30/2019 at 12:45

I think the internal regulators were junk. I had one that literally melted off the main power wire. When I had it tested it tested perfect, despite smoking out the testing machine.......

benn454 > MasterMario - Keeper of the V8s
10/30/2019 at 12:46

The last good looking F series.

Urambo Tauro > MasterMario - Keeper of the V8s
10/30/2019 at 15:49

So unds li ke it’s time to whip out the multimeter and test for voltage drop. With the engine running, are you at least getting a good charging voltage at the alternator’s “B” stud?

AMGtech - now with more recalls! > MasterMario - Keeper of the V8s
10/30/2019 at 15:55

I’ve been working on so many electric smarts (garbage!) that my first thought was “how does a 93 Ford have a charging problem? Did he convert it to electric?”

Anywho... My suggestion would be to check voltage output right at the back of the alternator. If that’s good, do a voltage drop test across the positive and negative cables. By that I mean, for the positive cable, put one lead on the alternator output and the other on battery positive, more than .5v there would be too much and even .5v is more than I'd like to see. For negative, one lead on alternator housing and the other on the battery negative. Again you're looking for less than .5v at the very most. Do these with the engine running and electrical consumers (defrost, blower, lights) all set to max. If voltage drop is too high it means your cables are acting as resistors and effectively "using" voltage.

MasterMario - Keeper of the V8s > AMGtech - now with more recalls!
10/30/2019 at 16:00

While that would be cool to convert it to electric that also sounds expensive and labor intensive.

I’ll have to check this. “Check the cables” seems to be a running theme.

AMGtech - now with more recalls! > MasterMario - Keeper of the V8s
10/30/2019 at 21:37

Voltage drop is the fast, easy, scientific test. Much much more reliable than looking at them, peeling back insulation, or even just a basic resistance test. Because it shows you what the wires do under load. You can have good continuity with an ohmmeter but still fail a load test, especially on something like that that carries a lot of current.