Ive been having problems with my charging system and tired of shorting out voltage regulators and alternators. 78 f250 idiot alt light. Wiring is all hacked up between alternator, solenoid and voltage regulator and I need to fix it. I need to know what color wires come off the alt and where they go, same for the wires coming off the voltage regulator. Then I need to know where the wire goes from the voltage regulator 4th slot I for idiot light in cluster. Mines missing this wire so the light never comes on.

Can someone decode my vin and tell me everything about my truck?
Vin is F26HCBE0468.

 

The GREEN with RED stripe wire coming from the cab connects to the 'I' input of the regulator. Note that if this truck was originally wired for gauges, the GREEN with RED stripe wire is sourced differently. If that's the case, you should make that clear.

The STA stud on the back of the alternator connects to the 'S' input of the regulator. If you have a factory electric-assist choke, the STA stud also branches to that.

The 'F' output of the regulator connects directly to the FLD stud on the back of the alternator.

The large output terminal of the alternator (sometimes labeled BATT or B+) connects to the battery side of the starter solenoid through a fusible link as well as the 'A' input of the regulator.

That's all.

I don't understand what you mean by "shorting out" voltage regulators and alternators. That's a vague statement with no electrical meaning.

Please start another thread with your other question. There's no sense in having two completely unrelated conversations happening in this thread.

 

F26HCBE0468
F26=F250 4WD pick up
H=351 2bbl V8
C=Ontario truck plant
BE0468=1978 model year serial number

A bit of advice, listen to fmc400. He's the goto guy for electrical problems.

 

Thanks fmc, when I fix this wiring does it matter what gauge wire I use? Can I use gauge 10 for all of it? By shorting out I mean a few months ago my alternator died. No volt output. I replaced it and that one had a bad diode. Finally a 3rd one has the correct volt output and no amp draw. Well all was fine for a few days then I had another dead battery. Checked all the wires and had an amp draw on the voltage regulator. 6.3 amps to be exact. I took one out of a parts truck and it ran fine until last night. I drove home during a rainstorm and lost all power driving 55mph. Lights wouldnt even turn on. So I put the old one back in that draws amps and the truck runs fine. But I have to unplug my battery again or it will drain it.

By all the problems ive been having im guessing I have a short and im not going to throw money at it to fix it. All the wiring near the alternator has been hacked up by p.o thats all I see thats been hacked besides my dome light. I just want to fix the wiring before I waste more money.

 

Im going to make a new thread about this. Have a few questions.

 

Update for fmc: I do not know if originally it had gauges or idiot lights. When I bought the truck it had idiot lights. The oil light works, it comes on sometimes on steep hills or while going fast around corners. Not sure if that answers your question or not..


You said the wire for the idiot light comes from the cab. I assume that wire goes all the way accross the firewall and comes out by the regulator in the main harness right? If yes I will go look for it and let you know. If it did have gauges where would the gauge wire be? I will also check this to help.

 

CHECK YOUR OIL LEVEL!! If your light is coming on like that your oil level could be low.

 

I check it everyday it reads fine on the oil dipstick flat surface cold motor. I think I need an oil change. I do alot of driving back and forth to work everyday. Maybe even 40wt.

 

And Mike is the guy for pretty much all things dentsides Thanks for the kind words Mike.

Wire gauge always matters.

Without tearing apart a harness, I wouldn't be able to tell you the recommended AWG off the top of my head. But the wires running to the 'S' and 'F' terminals, as well as the branch running to the 'A' terminal are lower current relative to the main alternator output. 10 AWG is overkill. If it were my truck, personally, I would use 16 AWG for those three.

The main alternator output feed to the starter solenoid must be heavy gauge; it depends on what loads you are running. Not to pass the buck, but I would be curious if Mike would know the factory sizes off the top of his head since he has a lot of experience with NOS harnesses.

Based on your description, I agree that it makes more sense just to restore the wiring to original condition. The voltage regulator connector is available aftermarket.

All of this sounds fine. There should be a two-prong plug along the passenger side inner fender carrying a WHITE with BLACK stripe wire and GREEN with RED stripe wire. It does come from the firewall but there should be access toward the front of the truck.

I only ask about gauges because if your truck was originally set up for gauges, but an idiot light cluster was swapped in, the light would not work without modification behind the dash. This does not appear to be the case.

 

I found the connector with white wire and black stripe, green wire with red stripe. The green wire with red stripe goes to the S input on voltage regulator and white with black stripe goes to sta on alternator. I input on voltage regulator is empty.

Also A input on voltage regulator has 2 wires, one looks like a fuseable link that is cut or broke off and no sign of the rest of the wire

 

Then the truck was wired for gauges and the cluster is not correct for the vehicle.

 

Ok thanks I will look for a new cluster, any idea what the fusable link is for? Or is it something else? Or can I make my current cluster work?

Could it be possible that when the p.o hacked up all these wires that he put the wrong voltage regulator connector on? I ask because I thought dash clusters used different connectors. Idiot light being a smaller connector and gauge using a bigg connector? Or was that bigger connector for 73 to 76 and smaller for 77 to 79?

I remember trying a gauge cluster out of a 74 or 75 and it needed a bigger connector.

 

Right back at you Jeff, thanks.
To the OP.
I looked up the alternator harness for your truck. There are four possibilities, depending on alternator output and whether you have gauges or lights. I doubt you have the 70 amp alternator, that wasn't a very common option, so that reduces it to two, depending on gauges or idiot lights.
Wiring harness, alternator
with lights D8TZ-14305-C
Green Sales, Cincinnati, OH has 40 (800) 543-4959

with gauges D8TZ-14305-D
Don Sanderson Ford, Glendale, AZ has 1 (623) 842-8643

 

Fusible links are used to protect heavier-gauge wiring. They are used over fuses for ultra-critical, low-risk applications and are better suited for under-hood applications than fuses.

I don't understand what you're asking. What is "it"?

Are you the same guy with all those cluster questions a couple months ago? Is there more to the story here with regards to what has been touched?

There were several clusters throughout the years. If the connector physically fits, then technically it can be repopulated to work (where "work" is defined as all lights and needles operating properly). However, the connector should not fit into an idiot-light cluster if the truck was wired for gauges.

Aside from the pinout to the voltage regulator, the other difference between light/gauge trucks is how the GREEN with RED stripe wire under the hood is sourced (per my earlier post). For trucks with an ALT light, the GREEN with RED stripe wire starts at one side of the ALT light, and hence runs up to the cluster connector. For trucks with an ammeter (amp gauge), GREEN with RED stripe is direct hot-in-RUN and START off the ignition switch, and as such, has no reason to run up to the cluster connector. As such, if the truck is truly wired for gauges, the connection to the cluster required for the ALT light is physically not there without rework.

If you see any cut wires at all, then it's anybody's guess as to what happened.

If your truck is truly wired for gauges, my advice would be to leave it wired for gauges, forgo the ALT light, and use an aftermarket voltmeter (which I think everyone should use anyway). There is not much use for either factory means of indication, in my opinion.

 

Yes you helped me with a cluster issue, I had wires behind my dash that were cut. They were identified as the wires for the radio connector and I had a ground that was not grounded. This truck was brought to a ford shop when I had the cluster issue (no dimmer lights) they confirmed my dash cluster wiring was not hacked up. My cluster is an idiot light cluster and the connector fits the cluster. All lights work besides the alt light.

Back to the voltage regulator: yes all of the wiring here is hacked up. I personally believe my truck had an idiot light cluster and the p.o didnt know how to wire the alt. You said if it originally had an idiot light cluster the green with red stripe wire goes to the cluster connector. If gauges the wire goes to the ignition. I will go look and confirm the location.

Edit: I checked and the green wire with red stripe goes to the number #3 pin on the cluster connector. So does that confirm my cluster is original? If yes I wire my alt and regulator exactly how you described earlier right? I will eventuanatly go to an aftermarket gauge but for now I want it wired corectly.

This isnt really about the light more about fixing hacked up wiring so I dont have to unplug my battery everytime I stop and stop shorting out alts and regulators. If the light works after this hey thats great if not im fine with that.