Charging issue vs. bad ground?

[BigNate]

I'm making a few strides in getting the old beast ready to drive but found a new issue.

Seemed I was only getting 7 volts out of the alternator. I replaced it, started it up and measured 13 volts. A short time later with it at idle I measured 12v. I thought I'd fixed it. Not so fast!
Let my youngest drive it around the yard a bit and it died. I jumped it and it started right up. Drove it up to the shop, and while I left it idling outside the shop so I could move the SD it died again. I jumped it, left the lights off, and moved it. Left the lights off, at idle, and went back to putting the SD in the shop. I went back out, pulled the lights on and after a few minutes they started to dim.

Is it a charging issue or a short to ground? How can I narrow it down?

Also, on the back of the alternator, I have three wire connectors Black (batt), Orange, White. I don't know what the Orange and White are for but there was also a jumper wire added to the Orange post going up to the start solenoid. My book doesn't explain why just how to hook it up and no troubleshooting. Any help is appreciated. I suck at electrical troubles.

 

[DNFXDLI]

Here is a link to a very good manual:

http://www.fordtruckfanatics.com/forum/showthread.php?t=29167

 

[BuzzGun79]

it is good mechanical practice, to replace the voltage regulator on these trucks when changing alternators....it could also be your issue.also give that wring and regulator pigtail a good look over for corrosion.

 

[BigNate]

Thanks for that link.
I'll probably replace the voltage reg, it's about the only electric item I havn't replaced. Was considering going to a single wire high output Alt. Have any of you gone this route? What if any issues do I need to consider?

 

[Mil1ion]

The alternator is merely the dynamo.
The VR is what increases and lowers the voltage.
The VR doesn't even "kick in" until about 900 RPM

You can measure output by running engine at 900 rpm....then ...one at a time ....add power drains.
Heater Motor, Headlights, Windshield Wipers all the while observing the voltage at the + battery cable.

Never try to diagnose electrical issues without first charging the battery with a battery charger.. Don't rely on the battery as is.

 

[BigNate]

This truck is a mess!
I charged the battery, started it up, and with no additional load voltage started dropping. I lifted the positive cable from the battery thinking it may have a bad cell. It died immediately. With th cable off I put the trouble light in series and it lit up. So I have something bleeding voltage when off, and charging issues.I'm beginning to wonder where it ends.

 

[m78]

I had a brand new alternator that had short right to its own housing that would drain the battery in 3-4 days.

 

[Mil1ion]

" I lifted the positive cable from the battery thinking it may have a bad cell."

Doing this is BAD and can ruin an alternator because the power-ground has disappeared causing diodes to fry. The power has to go a storage cell not thin air.

The practice you did was from the days of GENERATORS...
Sometimes Generators had to get the dynamo working so Mechanics did this with the positive battery cable to "EXCITE"the generator and get it charging.

Check your VR and see if where it attaches on the inner fender is not corroded.

You must run the engine at 900+ rpm to check the charging system.
The VR is what kicks in producing more power to the system.

You are using a multi-meter to check current..correct ?

 

[BigNate]

Been a while since I posted but thought I'd bring this back around.

I ran the idle speed up as far as 1800 to verify that the alternator was in fact spinning fast enough to pick up regardless of the point as I've had the quoted point as low as 800 and as high as 1700. No change in voltage.
With it running I started adjusting the volage regulator and went both directions with it seeing no change. The mounting is clean and to be sure I even tried adding a ground to the case. No change.
The harness looks bad but shows continuity all the way through.

So I ordered a one wire alternator and will be weeding the mess of wires & voltage regulator out.

Can't wait to get into my shop but it's a waiting game until I can get the concrete poured. Working outside this time of year isn't pleasant.

 

[fatherdoug]

Did you replace the voltage regulator? I know you said the ground point is clean, but is it tight also? I went through two alternators before I realized that the mounting screw for the regulator(ground point) was slightly smaller than the hole that it went into, thus not providing an adequate ground.

If you go with the one-wire alternator with an internal regulator, then that problem is solved.

 

[BigNate]

I pulled all the grounds on the block, frame, VR, and cleaned them all. Tightened them down and sprayed battery post laquer on them. I tried a spare alternator from my Son's truck, and decided against stealing his in service VR.

For me it boils down to simple reliability. I need a new voltage regulator and want a higher output alternator anyway. I just decided to go with a one wire. It eliminates an extra failure point, plus the assosciated wire mess that went with it. A new one wire needs a ground added at most. The VR looks to be quite new as is the start relay so I'm thinking the previous owner was having issues before we got it.

I won't know if I've found the issue for sure until I know. The wiring under the dash, ( and up the A pillar now ) is an absolute mess. Once the basics are working well it's the next nightmare I'm going to have to face. I hate wiring issues.