Charging system problem
 

Went to start my stock 1967 stepside.
Connected the battery, turned on the ignition, and noticed smoke under the hood. Disconnected the battery and found the main red 12v wire that goes from the battery across the top of the radiator to the main harness had grounded and melted.
Also noticed the ammeter was pegged to the right and remained so.
Replaced all the wires from the battery, lights, and ammeter fuse back to the main harness in front of the firewall.
Started the truck and observed the voltage across the battery at 16.-17 volts.
Figured the regulator got fried, so replaced that.
Battery voltage before start: 15.6 volts. Battery voltage now when running: 15.4 volts.
Swapped out the alternator and got the same results. I have 12.5 volts to the regulator and alternator. All instruments in the cab work just fine, with the exception of the ammeter which is still pegged to the right and does not move.
I figure the windings on the ammeter got cooked, but cannot understand if that would affect the charge rate. I even put the old regulator back in and sure enough.... 16.5-17 volts again with the engine running.
No rodents in the garage.... sealed up like a boat. Most of the wiring is new.
Any thoughts on where to look? I am out of ideas.
Thanks

Re: Charging system problem
 

I fought similar battles a couple years or so back. Fried wiring, ammeter pegged, serious overcharging. Had a mechanic work on it, tried new alternators, new voltage regulators, no good.

Finally converted to an internally regulated alternator & upgraded some wiring, with help from great people on this board. Lemme find that thread (there's a lot of my frustration, but the right answers are there too).
The difference, though, is you are now getting proper voltage at the alternator, while mine was too high before the internally regulated alternator. So maybe not the same problem after all.


EDIT: Here's the thread, hope it helps. http://67-72chevytrucks.com/vboard/s...d.php?t=772236 Good luck!

Re: Charging system problem
 

Mine cooked the wire across the radiator when I first got it running. I swapped to a 10si alternator and haven’t looked back since. It’s as easy as jumping the 4 wires at the voltage regulator plug and installing the new alternator.

Re: Charging system problem
 

At 12.5V, a battery is not fully charged. While I'd say that 15.6V while running now is a bit high, it's not that far off, and may be because of the low battery charge state. Pull a battery cable off and put a trickle charger on it until it reads 12.6 and a bit more. Then take the charger off, leave the battery disconnected for a day and see what happens. it should not be under 12.6V when you check it again. Yes, that regulator is toast. I will say it, but it may not be needed- the top of the battery should be clean and dry. I couldn't tell you how many times a customer came in with a dead battery on wet days, and the top of the battery was just filthy. I'd put a voltmeter on it at different places on top of the battery and show them that all the wet dirt was letting current run across the top of it. I'd clean it, charge it, and check it. Sometimes they were at the end of their lives, but usually they were just getting drained by being wet and dirty. I tried hard to make sure that I was right without fleecing the customers. Of course, a nice clean new battery would have done the trick every time, but would I really want to look that thief in the eye every morning in the mirror? Nope.

Re: Charging system problem
 

If the amp meter is peged check both of the amp meter fuses.

Re: Charging system problem
 

Thanks for the replies.
Correction to original post:
Battery shows 12. 6 volts with ignition off, not 15.6 volts.
Drops to 12.45 volts when motor is running.
Battery is 6 months old and fully charged. Terminals are clean and tight.
Alternator is off another C10 and works fine.
Perhaps "new" regulator is bad..... wouldn't be the first time that has happened.
One wire alternator is great idea, but having just rewired the front of the truck I am not going to hack everything up again.
Both fuses to the battery gauge are good, as are fuse holders.
Red wire across the top of the radiator, often referred to as a "shunt wire", was replaced with 12 guage primary wire. I don't think that would affect charging rate.
Gotta wonder if the "sensing wire" to the alternator is bad, however it's all new.
Keep the ideas coming I am out of ideas myself. Thanks.

Re: Charging system problem
 

You don’t have your plug on the alternator installed backwards do you? That will cause the alternator to go to full output. As for the alternator swap, I didn’t run a 1 wire, I used an internally regulated 10si. It’s as easy as cutting the old voltage regulator plug off, and splicing the 4 wires that remain together. Like this:
http://67-72chevytrucks.com/vboard/s...d.php?t=362957
The benefit of using the later alternator other than internally regulated is you also get more charging amps.

Re: Charging system problem
 

Since changing the ammeter fuses doesn't make the guage work. It is likely you have upset the balance of the ammeter loop when you replaced what you are referring to as the "Shunt Wire". (Actually the main battery supply wire to the truck. All charging of the battery and discharging of the battery with the exception of the starter, goes through that wire)
GM carefully selected the wire sizes and lengths to allow the shunt ammeter to work. Basically you have to have the exact same resistance as GM designed the system to have. (Don't ask me what it is as I've never seen it in print. But I know that is how it works.)
Have you had the alternator and regulator tested on a test rack? It sounds like one of the 2 components is not working at full capacity.
If you have not seen this link before it may give you some insight to where the problem lies.

http://www.madelectrical.com/electri...evymain1.shtml

Re: Charging system problem
 

Thanks, HO455. Great attachment. Will explore and advise what I find.

Re: Charging system problem
 

There's supposed to be a fusible link between the battery and the junction on the fender.

Re: Charging system problem
 

If I'm not mistaken, when the fusible link fails nothing will work.

If I am mistaken, someone will point it out. :)

Re: Charging system problem
 

Yes that is correct

Re: Charging system problem
 

What's the point of the quoted post?
The purpose of the FS is to save the wiring in case of a short. The OP and one response both say the wiring got cooked which means they didn't have an important piece of the puzzle.

Re: Charging system problem
 

Long story short -- When my wiring went up in smoke, the fusible link was in place and intact.

At a much later point in my electrical saga, the fusible link failed and everything went dead.

Electrical gremlins can be annoying, especially if their timing is bad. Like when you are in traffic....

Re: Charging system problem
 

Truck was rewired years ago....and fusible link left out.
Still haven't located the problem, but will take out the instrument panel and have a look behind the dash. Everything under the hood is correct.

Not sure why this post was moved from previous location as I doubt any '67-'72 owners with knowledge will look here. The moderators must know better.

Re: Charging system problem
 

I can understand your frustration but moving your thread here was the absolute thing to do. We specialize in electrical problems on 67/72 trucks, and your replies are from guys who hang out here.

Your problem stems from the alternator and or regulator not being able to sense the voltage of the system circuit. When this happens the alternator will
default to full output voltage. This can happen when the regulator fails or the sensing wire (blue) to the alternator opens, or the red wire to the regulator opens. Or if the regulator body isn't grounded to the radiator support.

I doubt that your alternator is at fault since you have purchased a new one, same with the regulator.

I question why your fusible link link wasn't reconnected and where you are getting your main junction wiring from.

Your wiring should look like this. the basic charging system.



Attachment 2019644


The shunt is located on the harness above the radiator and if It is not connected to the battery positive (fusible link) the ammeter will only receive voltage from the alternator side of the circuit. This could explain why the ammeter reads to the right. I think this was mentioned earlier.

Check your regulator for a good ground.

Check your wiring and compare it to the diagram.

The ammeter has nothing to do with the ability of the alternator or regulator to function. It just measures the voltage differential between the two and relays that to the driver.

If you decide to convert to an internally regulated alternator let us know and we will offer good advice.

Re: Charging system problem
 

Thanks, VetteVet
Will trace everything this weekend and post results.
Note that I have 12.6 volts, ignition off, at the battery.

With ignition on, motor running, I have 12.5 volts at the battery. I don't have full (17 volts) charge at any time.... that was with the old regulator which I presume was fried when the hot wire went to ground and created this dilemma.

Re: Charging system problem
 

Update
Traced all wires shown on the diagram, as well as checking both ends of each connection. All good.
Checked all grounds, including connections. All good.
Battery voltage, engine off: 12.5 volts.
Battery voltage, engine on: 12.3 volts. See pictures attached.
Replaced china regulator with one made in the USA by standard products - no change.
Lights on, motor running: draws battery voltage down to 12. 1 volts.
Four questions come to mind.
1. Does the sensor wire to the alternator see any voltage? With the motor off, there is no voltage.
2. Since main wire from battery was grounded, could anything had the polarity reversed? I've seen this a few times on some old positive ground tractors. Flashing the field coils corrects the problem. I realize this truck isn't a tractor with a generator.
3. If I put the old regulator back in, the battery shows 13.5-17 volts, depending on engine speed. This would indicate the alternator is working.
4. In rewiring the main 12volt line from the battery to the (1) regulator, (2) alternator (3) battery gauge fuse and (4) back to the main harness which goes to the firewall, I had to replace the original crimped "welded" connection. I chose to use 2 -12 gauge pigtails, rather than putting all 4 wires together as was the factory wiring. They are all connected together, not just at one common point. I can't see this making a difference, but am out of options.
Apologies for the lengthy message... trying to be as detailed as possible.
Thanks

Re: Charging system problem
 

If you have a Chinese regulator, and a Standard Products regulator, and an old regulator, and the only one that allows the alternator to work is the old one, I would say: you have 2 bad regulators and an old one that allows the alternator to put out a little bit too much voltage. If you got the Standard Products one recently, take it back and get a warranty exchange.

Re: Charging system problem
 

The old ones are supposedly able to be serviced, including adjustment. Some people restore them. I've read it somewhere on the Internet, so it must be true. :-)

Re: Charging system problem
 

Pulled the functioning regulator off another truck.... same results. So I know it isn't the regulator.
Is there anything under the dash that could cause this?
Again, does the sensor wire have voltage, with ignition off?

Re: Charging system problem
 

Yes do you have power from the battery to the alternator at the output post?

The white wire to the alternator should have 12 plus volts with the key on and zero volts with the key off. The blue wire should have 12 volts constant. Check the red wire on the regulator plug for 12 volts constant.

here's a video. https://youtu.be/N1JKKUfgCtk

Re: Charging system problem
 

do you have power from the battery to the alternator at the output post?
Yes

The white wire to the alternator should have 12 plus volts with the key on and zero volts with the key off. The blue wire should have 12 volts constant. Check the red wire on the regulator plug for 12 volts constant.
There was no voltage to either the blue (field) wire or the white wire with ignition on or off
Regulator is grounded.
I took the cover off the regulator and closed the points while the motor is running. Got 13-14.5 volts, depending on engine speed. But when I turn off the ignition, the points open and do not close when the motor is started. I turned on the lights also. The points did not close. Bad regulator?
What does the brown wire going off the bottom of the regulator back into the firewall do?

Re: Charging system problem
 

Ok now we're getting someplace.
That brown wire is the exciter wire that tells the regulator points to close and send current to the alternator to charge the fields and produce output. When you closed it manually that's what happened.

That wire provides the key on hot juice for the regulator and it comes from the key switch to the cab side of the firewall junction and connects with the brown wire on the engine side.
The cab side is a 24 gauge resistor wire which is connected to the accessory terminal along with a 12 gauge brown wire on the key switch. The resistor wire is the power for the regulator brown wire to close the points in the regulator.

NOTE: the 67 year key does not have an accessory terminal.

You may not be getting a connection between the two in the firewall junction or some one may have cut the resistor wire out of the harness not knowing what it is for.

Here is the key switch diagram. The black arrows show the resistor wire and the 12 gauge brown wire.


Attachment 2020976


They continue to the inside of the cab junction (resistor wire) and to the fuse panel (12 gauge brown wire).


Attachment 2020974


Fol;low the wire just below the brown wire on the key switch down to the lower left to the inside of the cab junction connector. If you pull the fuse panel you can see all this wiring. There are two 1/4 inch head screws diagonally in the corners of the fuse panel which hold the panel in place.


Here is a standalone of the wiring. It shows the wiring for a light gauge instead of the gauge dash with the ammeter. the gauge dash doesn't have the wiring for the light.

Attachment 2020975

Re: Charging system problem
 

Thank you for the detailed information.
The brown wire coming off the ignition switch was, indeed, disconnected. The odd thing is that it was connected to the two green wires at the base of the ignition switch plug. According the wiring diagram, that is for the temp idiot light. I don't have an idiot light for temp indicator.

I checked continuity for this brown wire at both ends, disconnected from the regulator. All good. I also installed a new ignition switch plug as the old one was in really bad shape.

Concern now is that the regulator connection for the brown resistance wire is showing a chassis ground. Not the wire itself....just the terminal at the regulator.

If that terminal is grounded, does this indicate the regulator is bad? Perhaps manually closing the points with this wire hooked up fried something in the regulator.
Pictures of the new ignition switch plug and wire connections. Note the only wire remaining is the brown wire and the accessory pigtail.