I have a 1982 F100 w 300cid AC/PB/PS 3sp Manual.
I am geting 12.3 volts at the batery while running. I have no idea what to do.
Alternator is new. Since it did not solve the problem I took it back and on the tester it is fine.
Batery is new. I even opted for the bigest batery that could fit in my truck just so that I would have longer between charges.
Both Cables Pos and Neg are new.
Wire from Alternator to regulator is new. (Can't get a new harnes, so I made one.)
All this and I still have to get towed if I go to far from home. I joke and call it a Hybred because it requires both gas and a power plug! But it is starting to get to be less funny.

I remember a thread a year or so ago (cant find it now) where someone installed a higher amperage AC-Delco alternator and it bolted right up like it belonged. That solved there problem. Does anyone know about that fix? Does anyone have any more ideas? I am about ready to set this thing on fire.
Patrick

 

Patrick, you didn't mention changing the regulator. A faulty regulator could easily be the cause of your symptoms and a new regulator may be much more cost effective than setting the truck on fire.

 

New Regulator too. And I still have the matches ready.

 

12.3 volts is a little low unless you are giving it a lot of amps. do you have a way to see how many amps you are drawing. Wondering if you are running at max amps for the alt., this would cause the loss of power on a long haul. Don't give up yet!! Give the poor truck a chance.

 

That 12.3 is under zero load. Turn on the headlights and you are at 12.1.
I am not sure how to check the amperage being drawn/given. On my volt meter, at the batery if i put it on the ACV (750) point it reads 25. Is that the volts? All of the options for DCA (200u - 200m) read 0.

The matches are safely in my pocket for tonight. I love this old stepside. But this has gone on for over two years now.

 

at 12.1 you are not getting anything back to the battery. sounds like a big draw somewhere. Have you had starting problems? Wonder if something on the starter side is drawing. We have had that problem with school buses and found this to be the problem. We had to replace the starter. Please keep the matches away for awhile

 

ACV on your volt meter is for Alternating Current like in your house. The DCA range at 200u - 200m is microamps and way too small to read amps on an alternator. You need an DC Amp gauge that reads at least 100 amps full scale. This gauge would be installed between the alternator and the Bat wire.

Are you reading voltage at the battery? If you are you should be getting between 13.2 and 14.2 volts no load. Then as you turn on accessories, the voltage should remain in that range until you max out the capacity of the alternator.

You can run a test that bypasses the regulator and puts the alternator in full output by disconnecting the plug on the regulator and jumping the Field Terminal to the Bat Terminal on the Alternator. If the voltage is not OK then the Alternator is bad.

If the voltage is now OK then put a jumper on the A to F terminals on the regulator plug. ( Regulator unplugged) If the voltage is not OK then the wiring harness is bad.

If the voltage is OK then the regulator is bad.

 

rocco makes a good point. You should be looking for around 14 volts at idle with no load. There are simple and fairly inexpensive ($60) testers available to check the entire charging system (i.e., battery voltage, alternator output under load, etc). Usually they can pinpoint or eliminate batteries and alternators, but they can't positively identify a faulty regulator. Using rocco's test will. If you don't want to spend the bucks, or aren't good at electrical work, most good parts stores have one they will use to test your system for free.

Good Luck,
Ernie

 

Awsom advice so far. Thanks.
BTW I put in a new Starter on Tuesday! Truck would not start. It made that electrical buzzing sound that I always associated with a starter going bad. Since it was freezing outside and there is snow on the ground I opted to have it towed to the shop. They replaces the starter and AFTER I paid them they said "The teeth looked bad but the starter worked otherwise." I prayed that the new starter may have been the problem too. Solved nothing. Same sound. They said they did not know what the problem could be! Required a jump to get it home where it sits on a batery tender untill I can work on it myself. That is why I came crying to you all.
12.1 to 12.3 is the reading directly at the batery.
This Saturday I will run JRocco's test, (if I can figure out where the A & F terminals are). I'd be willing to pay for the tool, but if it cant identify the failing part what use is it? I had them hook up one of those guages at one of those Advanced-Pep-Auto-Zone places. They could only tell me that there was somthing wrong with the charging system. Is the alternator bad? "I don't think so." Is the Batery bad? "Maybe."

 

When you do the test. 1st measure the battery voltage with the engine off. Then start the engine and jump the Field to the BAT terminal on the alternator. It the alternator is good the voltage should jump 1/2 volt immediately and keep on increasing as the battery charges.

If you look at the regulator plug you will see 4 pins and a blank space.
The terminals are looking at the plug end from left to right: I-Blank-A-S-F. Usually this is molded in on the plug or marked on the regulator.

The buzzing noise you are hearing is probably the starter solenoid mounted on the fender. You hear this noise when the battery is too low to start the engine. When you go to the start position a small coil in the solenoid moves a plunger that basically hooks the Battery Cable to the Starter Cable.

If the battery is too low there is not enough voltage to keep the coil energized so the solenoid kicks out. With the Starter now out of the circiut, there is enough voltage to pull the solenoid back in and and the cycle goes on and on. That's why you hear the buzzing sound.

If the battery is full charged and in good shape, and you get this sound then either the solenoid is bad or the starter is drawing way too much current. Then it is a bad starter, the starter cable is grounded, or the engine is siezed.

 

the starter thing can be a loose connection as well. I had a problem with that on my 77. costs nothing to make sure the connections are tight, and a new selenoid should run you about 5 bucks.

 

Yep, there were several things that would have been beter than spending $200 to get an unneccesary starter replacement. But that is done. In life there are two enemies. Haste and Indecision. Haste got the better of me in this case and I stupidly threw money at the problem. Hopefully the electrical system check will present the culperate and I can fix this issue once and for all. If not it is either more money throwing, or a bonfire. I havent decided.

 

You could have corrosion at any place on the starter connections. start from the battery and take everything apart and clean all the connections right down to the starter.

 

Have you checked for a bad fusible link at the starter relay?I am assuming you have a fully charged and GOOD battery.If you have an external regulator make sure it's clean and grounded.Be sure you have battery voltage at the back of the alternator.Check all grounds.