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Alt light glowing at higher revs

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billd View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 9:13pm
Here is some basic knowledge that will help many folks with basic troubleshooting skills (and no worries, not everyone is a born troubleshooter, just as not everyone is a good doctor or good attorney, etc.)

Power from battery to fuse panel to ignition switch, out ign terminal to connection at back of cluster, to bulb socket, back out to orange/black wire that goes to regulator AND to the "reg" connection on the back of the alternator. 
Now imagine how many connections there are. Geesh, just at the cluster you have the wire to the pin on the printed circuit, into and out of the bulb socket, the connection between the bulb and socket..... and so on......

Turn key on, system voltage (12.6 with engine NOT running and battery fully charged) goes to regulator and is send out to the field to "excite the alternator - make it start charging since alternators do NOT hold any residual magnetism like generator armatures do. 
So system voltage is 12.6 with engine off, this goes to regulator and then to green field wire to excite the alternator - give it some field power to get going. This is why the bulb is ON when the key is on but the engine not running - power through the bulb to the regulator, which is then fed to the green field wire, through the field to GROUND. So you have power to the bulb through the ignition switch, and it's grounded at the alternator.
Assuming all is well, you "crank" the engine over and it starts and the charging system starts to work - it charges and is regulated at for easy figuring 14 volts.
NOW the SYSTEM voltage is 14 volts. That's the pressure pushing on all wires that have power-  INCLUDING what goes to and through the ignition switch, to and through the dash ALT light bulb, and out to the regulator and REG connection on the alternator where that orange wire also goes.
Why does the orange go to the regulator AND the alternator? Because the power through the ALT bulb is just to tickle the alternator, excite it, but it's not enough to power the field when there's a real need..
Once the alternator starts kicking out power, it supplies some of that out the REG connection on the alternator, which goes to the regulator and the regulator now uses THAT to feed the field.
But that same REG terminal output also goes BACK to the bulb - remember, orange from bulb to regulator and alternator REG terminal.
Power through bulb to regulator to get things going but once they are going now suddenly there is power at the OTHER side of the bulb, too!  It's no longer grounded at the alternator through the regulator and field but now it has system voltage on both sides.
It is now being fed "positive" both through the ignition switch AND from the REG terminal of the alternator. 
At least that's the ideal..........
So what happens if you have a VOLTAGE DROP? You have an uneven or unbalanced system. 
And the dash ALT light is part of a complex system - the feed through the ignition switch, and back at ya from the alternator via the orange wire. 
A bad connection at one spot could cause a glow, but what if you had three bad connections, each dropping only half a volt?
Half a volt may not cause a glow, but 1.5 volts would.

And yes, strange as it may sound, if there's a bad ground, you can get FEED BACK from lights, etc. trying hard to ground back through other things. I've seen really weird things happen when a headlight, tail light, brake or turn light, can't find a decent ground. I've seen the turn signal indicator glow when parking lights were turned on - all due to a bad ground in a SOCKET.

Now enter the isolation diode. In the day it was a simple, clever, really pretty good idea (keeping in mind Motorola was among the very first with an ALL electronic charging system - alternator AND electronic regulator) and AMC was among the first to use them. 
That isolation diode has a certain resistance, enough to cause a voltage drop across itself.. That should be no more than 1.0 volts, I prefer about .8 volts and get edgy if it's 1.0
If that drop is greater, either due to a bad connection or a diode bad or going bad, you now have a bigger difference between the system voltage and what is at the orange wire at the REG connection..
With 1970 and prior systems, the reg connection actually reads just under 1 volt HIGHER than the system voltage or output voltage at the output terminal. 
So if the system voltage with engine running is 14, the reg connection terminal on the alternator will be 14.8 volts.
So 14 volts to the bulb through the ign switch, and 14.8 back at it from the other side, you already have a .8 volt difference. 
Incorrect bulb and it will glow.
Bad connection and it will glow because you are already on the edge - just not quite there. 
All you need is a single bad connection, or connections totaling .2 volts or more to add to the .8 difference already there and you have one volt or more - enough for a glow. 

All those words to say - you must check all connections, to and from the ignition switch,, fuse panel, fuse connections, dash cluster, bulb socket, is it the correct bulb and so on.

But if it's speed related, you need ask, what changes with the different speeds... movement, flex, belt slip/glazed belt, a theory I've not tested is - brushes worn to the point they make "ok" contact with the slip rings on the rotor inside the alternator when it's not spinning too fast, but not good enough when it's really spinning and they are bouncing around a bit more-  worn brushes can be weird, too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Blue68SST Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2018 at 3:46pm
Resolved! I cleaned all connections on the alternator, and the ground strap from the frame to the engine. None of them looked bad. I had a new fan belt as a spare, so I changed that as well. Took it out for a test drive, lights on- No glow! I probably should have taken it out for a drive before doing the fan belt, because I don't know if it was a connection issue or a fan belt issue. I'm just glad it's fixed. Thanks to all for the info/suggestions.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2018 at 4:43pm
Frankly, I'm rather glad you did all of them - these are not new cars, after-all.  ;-)

Connections - all it takes is a very thin layer of metal oxide to cause enough voltage drop to cause real issues. 
I have found cases in home wiring where removing a wire from a connection, a light cleaning and putting it back resolved odd problems. And that's 110 + volts!
Anyway, I "harp" on not being able to look and tell every time. Sometimes it works, but sometimes a person can miss a connection "barely bad" that drops even a tenth or two, where cleaning it means no detectable drop.  And if you drop a fraction at each of 4 connections, it can add up!

Glad it's resolved. Admittedly, electrical problems can cause one to lose their hair - or go gray (sort of like having kids)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2018 at 5:08pm
Billd, is correct and all his help with troubleshooting can go out the window, if one does not check all the connections for cleanliness and fit, before attempting any troubleshooting. That is why I gave basics first before pointing détails.

In the many years of repair work with electronics, simple disconnection and reconnection is enough to clean or make proper contact. The problem with older cars pré 80s, is the open to air connections. They tend to be the fault and create more faults with how the system is strained by loss of power through the connections.

You would think a lack of power would not strain a system, but it does. One, it will allow other circuits to bleed from each other, either from a ground stand point or main supply from fuse panel. There is no protection diodes to limit current flow from other loads, so the strain can come from A/C, head lights, charging system, and fan blower, or rear defroster if equipped.

Glad you found such a simple maintenance procedure can resolve and keep your charging electrical system proper.

I would recommend a simple maintenance as you have with the connections every other year. As a lack of operation is almost as bad as long term operation in the elements. Humidity happens, and it does get into connections and electronics no matter how well you think you take care of it.

We have to bake our electronic components before we use them on the bench for repairs. Even though they look sealed by the package, a sudden heat up to 250 degrees during soldering, ill make them pop like popcorn if left out and never baked before hand. Once baked the components are bagged and sealed for use, and are marked with how long the bag was open to the environment when a component was removed.





Edited by 304-dude - Jun/22/2018 at 5:13pm
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2018 at 6:11pm
Here's how little it takes in some cases - we used to have to pull cards from their slots in computers, run a pencil eraser over the contacts and plug them back in to solve really WEIRD things. The contact fingers looked fine and pulling and resetting them didn't always work, but an eraser almost always did.
Of course once they introduced higher bus speeds and newer bus designs, there were times the ORDER of the cards in the slots actually made a difference!
Anyway, it all goes to show - how little it can take. 
Remember, oxides are typically not great conductors and typically act like insulators.
And they can be very hard to SEE. 
(ever wonder why some connections using bolts or screws have "star" type washers, or the connector itself has an irregular surface like a "star lock washer"?
It's to cut in a bit for better connection, dig into the surface.

By the way, back on electronics, we used to run boards that had been soldered and completed through the dish washer - literally - to wash off all residue from soldering, any acids from being touched, rosins, whatever. The oils on your hands can cause bad oxidation of copper.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2018 at 6:43pm
Originally posted by billd billd wrote:

Here's how little it takes in some cases - we used to have to pull cards from their slots in computers, run a pencil eraser over the contacts and plug them back in to solve really WEIRD things. The contact fingers looked fine and pulling and resetting them didn't always work, but an eraser almost always did.
Of course once they introduced higher bus speeds and newer bus designs, there were times the ORDER of the cards in the slots actually made a difference!
Anyway, it all goes to show - how little it can take. 
Remember, oxides are typically not great conductors and typically act like insulators.
And they can be very hard to SEE. 
(ever wonder why some connections using bolts or screws have "star" type washers, or the connector itself has an irregular surface like a "star lock washer"?
It's to cut in a bit for better connection, dig into the surface.

By the way, back on electronics, we used to run boards that had been soldered and completed through the dish washer - literally - to wash off all residue from soldering, any acids from being touched, rosins, whatever. The oils on your hands can cause bad oxidation of copper.



Yep, the dishwasher... but in my case one big automated one, that resembles an automated burger broiler, but twice as long.

Back when Apple made the Macintosh, there was assemblers touching the contacts during assembly. The fix was a rubber pencil eraser. That is one thing I have always pushed for cleaning. Some use fine sandpaper or steel wool, but anything abrasive will leave small scratches for oxidation to occur. Plus wears on the contact surface plating if done too much.

Finger oils and or moisture on contacts is bad.

Pretty much all ground wire connections to chassis have a star lock washer to mount with, on the systems I worked on. Some of which were for industrial tractors and department of armed forces both sea and land.

Back on a past thread on crimping wires vs solder... All the crimped connectors were tinned to prevent corrosion, and the wires were tinned before being crimped. Then touched with an iron to seal. To the naked eye, it looked crimped only, until you cut some jacket material back to see its copper wiring, not alloy.

To keep your wire insulators from melting when soldering, an alligator clip will heat sink enough to make a clean solder without damage to the insulator. Another option, is use silicone jacketed wires. Which some fused links are on our AMC cars. The ones for alternator and A/C relay to the battery post terminal starter solinoid.


71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6768rogues Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2018 at 9:30am
Billd:
"ANY dealership that did that was an idiot. AMC addressed the issue and it can be resolved with basic troubleshooting. Sorry, but that's a cheat way out of FIXING an issue - if it glows, there is a problem, PERIOD!"
" Only a fool would paint a bulb instead of fixing the bloody problem."

Ok. Relax and breathe. Maybe you should switch to decaf and get more fiber in your diet.
The dealership had a customer with a glowing bulb. The system was still charging adequately. The customer did not want to spend money to restore it to 100% because the cars typically only lasted for a few years and most of that was behind them. Paint the bulb black, the customer spends little money, next year the car is shot and they junk it. That was in the era of shoving a banana in the differential to make it quieter, a few drops of brake fluid in the PS to swell the seals and stop leaks, and many other short term temporary fixes. Most of those cars had 80% to 90% of their expected lives behind them and had owners without money to spend. Slap a Band-Aid on it, in 6 months to a year the car is dead anyway from some other cause not related to the light. For a regular customer, the dealership fixed it for free while the customer waited. The customer is happy with their dealership experience and returns for another car, not feeling hosed for hours of diagnostic work simply to fix a glowing bulb.
I had a used 68 Wagoneer with the AMC 327. The bulb glowed for the entire time I owned it, the entire time the subsequent person owned it, and was probably glowing when it got crushed at the scrap yard. Sure, on a restored car it is nice to have everything 100%. That was not how the real world worked back then.


Edited by 6768rogues - Jun/23/2018 at 10:01am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2018 at 10:42am
The real solution, according to AMC TSBs is - replace with a different bulb AMC recommended, or in earlier years, AMC told the dealership to suggest the customer ignore it. 
In most cases, the fix is simple, cheap and quick if the tech knows their butt from a hole in the ground (apparently they were clueless and had to admit it was going to take them hours and cost a lot because they didn't know the cause)
Yes, AMC said that if a part wasn't available, etc. etc. tell the customer it's working, ignore it for now. 
The problem with painting the bulb - if a problem DOES develop in which the thing isn't charging, now the customer ends up with a dead battery.
There are repercussions of such foolishness as painting a bulb to hide it.
Didn't that ask themselves "what if it really fails? How will the customer know"?

I started in a shop that was part of a "Rambler" dealership. Trust me, I know about the "I don't want to spend $20 as I don't plan on keeping it" (frankly, how did the idea they didn't last that long come about? They lasted actually a very long time - we had customers with hundreds of thousands of miles, and Ramblers from the late 50s still going in the 70s - likely it was lack of a good dealership, etc.)
anyway, we knew how to deal with "cheap owners" - such as Coke bottle of water down the carb with running engine to deal with carbon knock........... we did it for free.  We knew how to deal with certain rough idle issues - esp with the AMC 6's - cross 3 and 4 plug wires, let it pop a couple times or so and put 'em back. It blew the crud out of the idle circuit and solved some rough idle situations. We did that for free, too. 
Not talking about restored cars here - talking about daily drivers people relied on. 
that's a thing we'd never have done - because it only leads to more trouble - and we knew how to fix things, we were troubleshooters, unlike most "mechanics" then and now.

Sorry, I still maintain it was due to a mechanic's inability to troubleshoot and find issues in a timely manner, and understanding the system they were working on. 

By the way, brake fluid won't swell seals - or it shouldn't.............   ;-)
If it did, well, a lot of brake valves and other devices would be malfunctioning. I use brake fluid to lubricate certain o-rings and other seals during assembly of certain items. 

And you also supported AMC's instructions to dealers to tell customers "ignore it" as you said the bulb glowed the whole time. 
Of course that's also a calculated risk as it may indicate bigger problems being ignored.
Amazing how so-called mechanics got away with crap over the years - maybe that's why they to this day have bad reputations with so many people. One of the least trusted people out there is a mechanic. and I see - with good reason.

OF course in this forum - suggesting "paint it" or "ignore it" isn't going to fly because we have people from all over the world looking in and they see such things and gee, I can simply ignore it, it's normal, it's ok - and no, it's not.
If things have been tested and shown to be functioning as far as proper voltages and charging rates, that's one thing, but to simply say "if it glows you can ignore it" or "it's normal" - not good to propagate bad or incorrect info.
It's not normal and it does indicate a problem -- one that may bite 'em in the arse later on.
No one is talking about RESTORING - we are talking of reliability, preventing things going south later, making it dependable. No one mentioned a full restoration. 
It doesn't take hours to diagnose that issue - under an hour if the person knows their head from........ and has any true electrical experience. If you think hours, then the mechanic needs to be trained, or find another job.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Samuelsc360 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2018 at 1:15pm
Our dealership put in bulbs of a slightly higher rating. It would stop the faint glow but still light up during a problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6768rogues Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2018 at 1:27pm
I did not instruct anyone to paint or ignore the glowing light. I simply stated that dealers used to paint it. Some of the customers had little money, hence, they were driving second hand Ramblers. The dealers were trying to save them some money by doing something that was cheap. Yea, they might end up with a dead battery if the car lasted long enough for something else to break. Dead batteries, jumping the car to start it, pushing it to a start, etc. was so common back then that everyone had to do it from time to time. There are a lot of people on this forum who were not around when the cars were in common circulation and who have no idea what was done back then.
Some cars did last a long time. I also remember seeing three to five year old cars with the spring towers so rotted out that the spring came up through the hood. My first Rambler rotted so badly that the transmission crossmember failed and the tranny almost fell on the ground and it had not hit 60,000 miles. It was not just AMC cars, most cars with over 75,000 miles and 3 to 5 years old were considered as really old cars back then. The only further comment I want to make is that characterizing the people who did quick fixes back then as "idiots" or "fools" is not very constructive to the conversation. Nuff said.


Edited by 6768rogues - Jun/23/2018 at 1:33pm
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