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So some of you more edumacated automobile mechanics will put together my other thread with this one and laugh at me, but that's ok. I am not sure if my circuit warning box had anything to do with it, but maybe someone can surmise further...

My Tuff Stuff 80 Amp Alternator purchased at Summit about a year ago but hardly used is sort of dead. What I get at the main terminal is 50 volts or so. 12.47 at the R terminal, the one that is for the Alt warning light. Terminal 2 is jumpered over to the main terminal for now. Anyone know what I did? But then its not over there...

I have two other Delco 3 wire Alts. I took the one off an old beater and tried it. 100% dead. No voltage on anything. That didnt surprise me, but what DID was when I took the one off my 50 project (3rd alternator) and it was 100% dead too. Three bad Alternators does not make for a good day!

The last two that were 100% dead, I made sure to hook up an incandescent light bulb from the ignition switch to Terminal 1R on the plug, so excitation should not have been the issue.

So, have fun with this one, but please tell me after, is there a more modern, maybe better Alternator to use for these trucks? Has anyone made an Alternator that uses LED's for use with the Alt's internal warning circuit? (seeings how LEDs are being pushed so hard).

I use the newer smaller GM alternator if space limitations require it but the old internal regulator three wire is more durable. On my home made tester which is a 1/2hp electric motor, a belt, a pivot pin to run through the alternator mount, a tension handle, and a battery is wired exactly as you describe: jumper #2 to BAT terminal, and a 10g wire from that same terminal to the battery. I don't wire in #1 but just touch with jumper to excite and then use a cheap amp meter that just slides over the wire to the battery for a reading or hook volt meter to battery for a more precise read. Sometimes when I'm going through the pile I just excite and touch the rear bearing with a hack saw blade, if it sticks then spending a little time on testing and cleaning is on the menu. These are tough old units so three in a row dead is unusual. Many times these old 3 wire units will self excite if rpm is blipped to 3 grand or so and the #1 connection is not necessary. My half dozen or so various cars, trucks and machines are just two wired but if I forget to tell another user to rev it to excite the battery will drain. Too lazy to wire in a light.

I had a really nice conversation with one of the engineers at Powermaster. I learned a few things that may be worth repeating.

1) If you have 50 volts at the main terminal of your alternator, it means you have no load on the alternator. So, the problem ended up being an el cheapo fuse holder not making proper connection. All three of them are fine.

2) My local auto-electric repair shop guy told me that he doesn't like fuses in the main charging line. He cut me a 6 inch piece of Fusable Link line and said to put that in instead. On the other hand, the guy at Powermaster said to put a fuse inline because less damage would occur, like the difference between a fast blow and slow blow fuse.

3) Powermaster went on to say that a good way to resolve the 50 Amp meter using a 150 amp Alternator is to run a second charging wire direct from Alt to Battery. The second line acts as a bypass (shunt) and allows for an alternate current path. He was adamant that it makes more sense however to just put a voltmeter in your ride and just do away with the Ammeter completely.

4) Good news on more modern Alternator solutions is, the old Delco 3 wire Alts wouldn't charge until you hit about 1000 rpm (not sure but higher than idle) but the new 12SI ones they make have two advantages. One is, they start charging at about 500 rpm and the other is, they do not need any excitation wiring, they internally self excite. There is a plug over the two terminals and unless you want an alt warning light, this Alternator acts as a one wire solution. If you do want a warning light, it's a two wire solution. Pretty cool.

5) The last thing I learned was that it is perfectly fine to use an LED warning light. To do that, you need to put a 100 ohm, 1 watt resistor in series (before the LED or after) to limit the current the same way the incandescent bulb does. You read tons of things on the internet about this, all mostly conflicting with each other, but this was from Powermaster, so unless it doesn't work, I will feel on solid ground. More testing is needed.

4) I've never had any problems with a three wire delco alternator properly hooked up charging right off start with engine idling at 500 - 600 rpm. No reving required. The Delco one wire alternators do have to be reved up before they will charge.

If it's being properly energized it should charge without having to rev it.

I like fusible links rather than fuses on the charging circuit as well.

I also prefer a volt meter over an amp gauge after a 1966 Pontiac Catalina caught fire behind the amp gauge.

I'm surprised the alternator doesn't burn out if there is no load on the battery lug. Usually the voltage spike will burn out the regulator or the diodes or both. That's why they don't recommend removing a battery terminal while the engine is running to see if the alternator is working.

Sometimes folks get lucky though. Usually not me.

The Delco 3 wire I just got from NAPA yesterday starts charging at about 600 rpm. That's not bad at all. I agree on the amp gauge. When I have time I plan on doing the conversion using the Tech Tip here. I put the fusible link on my test engine so it didn't go to waste. Now that I understand Alternator operation better, I can safely work on electrical upgrades without doing any damage. Thanks again!

An A/C Delco rep came to the parts store I worked at to host a seminar on alternators and charging circuits. Was pretty interesting.

He demonstrated how the alternator could (would) spike a high voltage if the battery was removed from the circuit.

He also explained how the old three wire Delco operated and why Delco liked to use a sensing wire from a remote location in the wiring harness. (Most people make a short loop from one terminal to the other on the back of the alternator)

He also explained that the back of the alternator needed a good ground rather than depending on the 4 bolts that hold the two halves of the alternator together providing that ground.

So GM put a bracket and bolt on the back of the alternator to not only help to stabilize it, but to provide a good ground path for the end of the alternator doing all the work.

Was interesting, and several year back, so some now is a bit foggy. But I learned several things I had never really thought about.

Good luck to you on your endeavors.

What truck is a 150 amp alternator going in?

Thanks for posting the info! (I'm late to this thread)
Brad

It's a hypothetical based on empirical evidence that companies are pushing the biggest Alternators they sell to unsuspecting people. The Powermaster site goes out of its way to explain how bigger is better. They have even made them so cheap that it may make sense to some.

It's only better if you don't have a choke point in the line somewhere that can ruin your day, like a vintage full (current) flow 50 amp Ammeter. I would argue it's not better and totally unnecessary, but that's me. A lot of us who spend time in these technical forums fail to realize the masses out there equate bigger to better. V8 vs I6 is an example of bigger Power being somehow better in some people's minds. On that same theme, they might think a big alternator is a better idea than a small one. If there were someone on the sales end that helped the customer choose, there would be no need for this discussion. Modern Ammeters are not designed with this same choke point limitation. Most companies have switched to voltmeters anyway.

The ENTIRE point was to inform the public that if you have an Amp Meter that is rated at a maximum of 50 amps and you do not have a second current path around that meter, you are limited to a maximum current output of 50 Amps on your Alternator. If you go beyond that, you are exceeding the risk factor that GM builds into their systems and anything that happens is on you.

Powermaster even told me that to get around this problem, put a second wire on the main output of your alternator and run it direct to the battery so you have a path of least resistance to protect the gauge on vintage vehicles that have this old style of meter.

To mitigate the fact that you made an uninformed choice in purchasing an Alternator that is too big for your truck, I put out there that we can put a 50 amp inline fuse or circuit breaker in the main charging line or a fusible link. By the way, uninformed is a relative term since I am talking about ME. I decided to use it on my test engine so it's no longer a thought, but I like to warn others about issues I run across because if I did it, it's possible someone else might have to.

I am very grateful for the responses here because I am just trying to sort all of this out myself, and if during the learning process we can help others, that's what we are here for.

Deve: This is a good start for understanding and identifying what you have and, how it works. http://www.americanautowire.com/view-faq/how-to-identify-your-gm-internally-regulated-alternator/
AC Delco only but still an alternator is an alternator. Good find on the "lost" load.
Trouble shooting 101 step 1, check all connections.
Still the best and most important thing the Air Force taught me.

Removed and Replaced, Ops Check Good! Thanks! If all else fails we could always NRTS it.

Flight line guys are all the same. Black box tech. I don't care what is in the box, it don't work. NRTS it to the backshop. Backshop guys all the same. Ops good stick a yellow A cond. tag on it. Pilot still wants the radio to work in the OFF(other fine frequencies) position. Air Force wants the airplane back. And so it goes. Wait until you spend some time in the Fuels team or take a walk on the wild side with the ordinance folks, we did call them BB stackers I am sorry to say. Then there are the kind folks from EOD. Brave as ever. Me? I was "just" a civvy. No need to worry about him. Loved working with them all. Happy Veterans day.

I have re-written this post multiple times to try to make it make sense. I fear I may have failed. I'm pretty much a rookie when it comes to electrical rules/theory so I apologize up front for any ignorance. :-)

After reading this thread three times I think I understand what you are saying. I am a bit shaky on a few points. First, what is this talk about "excitation?" What does that mean?



Second, what is the purpose of the 50 AMP inline fuse in the main charging line? Is that to kill the power to protect the ammeter if the alternator produces more than 50 amps? Doesn't that defeat the purpose of the larger alternator? Or is that the whole point? If you have a 150 amp alternator but don't want to melt down the ammeter, you need to use the fuse, thus artificially limiting the output of the alternator.

Third, you need to help me understand how running a second wire from the alternator to the battery will protect/limit the amps to the ammeter. Are you saying that once the ammeter "pegs" at 50 amps, any excess amps will simply flow down the other wire and not overload/melt down the ammeter? Is that possible??

Larry,
The weather in New Orleans is bad this morning and I have been up since 2:30 am ,on my 5th cup of coffee.
I will try to explain in lay mans terms what you are asking.
#1 Excitation-- You are 55 yrs. old, out for a walk on a beautiful spring morning with your 50 Yr old wife at the [park, beach etc.]. A very attractive young (22 yr old) comes walking by in a very nice walking/running outfit.

#2 Yes, 22 yr.old is 150 amp alternator, 50 yr old wife is a very short 50 amp fuse and will Kill all the power to the amp meter which is you.

#3 Have no clue if that will work, But there is no reason to have a big alternator like that on an old truck. I think most of the vehicles that originally came with alt. were 32, maybe 45 amp alternators. So on an old truck what kind of draw would you have that you would need more than 45 amps?

As I said I'm on my 5 Th cup of coffee, so I may be wrong, but hopefully will make someone laugh.

Tommy,

Maybe someone with a Suburban wants to install an impressive surround sound 10,000 watt stereo, a powerful air conditioning system, multiple powerful spotlights for deer hunting, and want to be able to serve as a back-up energy source for their house/garage if there is an energy outage?

Tim,

You obviously have this figured out.

Tim,

You obviously have this figured out.

Larry you understand the problem completely. The ammeter is the bottleneck. And yes, running the extra wire will give the current the alternate path of least resistance and will save the Queen. I do not quite understand excitation either, other than the alternator needs to be positively charged to begin its charging function and some Alts need a second wire for that. (the one that is supposed to go to the battery but everybody just jumpers it over from pin 2 to the main terminal on the Alt).

If you want to actually use that big alternator, then the answer is to remove the original vintage full current flow Amp Meter and go with a Voltmeter. This eliminates the bottleneck.

For those of you who want to continue to use your current Amp Meter, put a 50 amp Fuse in the main line going through the Amp Meter and run another 8-10 gauge wire from the back of the Alternator directly to the Battery. This is from the engineers at PowerMaster, not from me. It looks to be sound advice. I have researched this until my [censored] falls off and this is the very best I have seen so far.

I know that others will say just put a shunt across the meter to do the same thing, but it really doesn't do the same thing. All of your accessories are run off one side of your ammeter. That one wire is busy enough as it is. This protects all of that because the excess current isn't even coming into the cab yet you are getting the full benefit of the higher amp Alternator. I do not profess to know really much of anything, I just research things until I understand them sufficiently to move on to the next conundrum. Email Powermaster and include our conversation. See if they concur. They were very nice in answering all of this for me to share here. I would also recommend doing some additional research on how to properly wire your Amp Eaters. Of course do not wire them in line with your Amp Meter. That has a 50 amp fuse on it!

Would a wire bypassing the ammeter be the same thing as installing a shunt across the ammeter terminals?
It this were true, would you not lose the accuracy/correct sensitivity of the ammeter?

According to the guy at Powermaster when I asked him about Ammeter accuracy, he explained that the same current is going down both paths so there will be no difference in ammeter accuracy. The current is not split evenly because more current is needed down the accessory line than the battery.

The shunt does bypass the ammeter, but all of the current of a 150 amp alt would go through that one path where all of your accessories are connected. It made sense to me to add a second wire. Also, if a big honkin fuse holder is a problem, a fusible link is more fashionable (as in undetectable if covered just like wire). Don't put it at the battery end though. Battery gasses could be ignited if that link ever blew.

He wasnt a fan of the vintage full current flow ammeter and really encouraged me to change over to a voltmeter. It's like I said Carl, you should contact Powermaster to confirm. I put things out there and try to be as accurate as I can, but nothing like talking to a real expert.

All your lights and accessories should already bypass the ammeter. The ammeter does not indicate amps going to the 10000 watt stereo from the alternator. It reads amps going to and from the battery. If you try to run the 10000 watt stereo from the battery without running the motor, it will peg the meter. That is why you have a fusible link between the ammeter and the battery. You DO have the fusible link, right?

Which is why Powermaster suggested to go to a voltmeter. If it's dangerous to put the fusible link at the battery due to the possibility of igniting battery gasses, that leaves putting it under the dash at the ammeter. I don't think anyone here would do that. If those are the choices, I would roll the dice and put it at the battery. That is not all of the choices. The reason I put my fusible link at the back of the Alternator is because it is the threat, not the battery or associated wiring. If a dead short happens, it happens along the entire line so putting it behind the Alt stops the threat as well. Not ideal, but until we get rid of the 50 amp gauge...

You went to a high powered alternator, do the wiring correctly which would include removing the old full current flow ammeter. Its a very worthwhile conversation to have. One of the things on my list is to do the Tech Tips mod to go to Volts. I will examine that avenue fully because it makes sense for those who want to go to a bigger Alt.

I think we have pretty much put the idea to sleep that doing nothing is an option for those who have higher than a 50 amp Alt.

Funny thing is I just stumbled across the wiring diagram book for my truck in some papers last night. Not sure how that got packed to go to Kuwait... I need to sit down with that tonight and reread this thread to see if it will make more sense.

To be clear, I have a Delco Remy 1102473 55amp internally regulated alternator in the truck. I simply asked the question earlier to try to get smarter on alternator and ammeter function. I posted another thread a couple of years ago about my ammeter. Right now it only shows discharge when electrical items are turned on (lights, radio, heater etc.). As electrical demand increases the needle drops further towards discharge and stays there. It never returns to TDC until all the electrical items are switched off.

When I got the truck the wiring under the dash was a mess. After of lot of time with a multi-meter and the wiring diagram, I slowly cut out a small pile of wires that came from/went to nowhere. It appears that when the original 235 was taken out and the 78-79 250 was put in its place the previous owner grabbed the engine wiring harness from the other truck and shoe horned it into mine. He only hooked up what was necessary to get the truck running. That is why there was so much dead end wiring under the dash/hood.

My theory is that during the engine swap and "re-wiring" of the engine harness, not all the required wires were hooked back up to the ammeter. That is why it only moves toward discharge and never shows any charging. The truck ran fine for over a year and never had a dead battery so I'm confident the charging system is functioning correctly, it just doesn't show on the gauge.

All that being said, I'd like the gauge to function as designed. When I return to the states I'll have to run all the necessary wiring in accordance with the wiring diagram to get it to work properly. I don't have any current plans to go to a bigger alternator. I was schooled on here that bigger isn't necessarily better. Its kind of like slapping a big 4 barrel carburetor on you Stovebolt because you believe that the bigger carb has to make more power. "If I'm running a 375cfm carb now than a 600cfm 4 barrel will give me twice as much power." Doesn't work that way! You only need what you need.

Wow. I that was a bit of a ramble and I may have hijacked this thread. I'm really only interested in expanding my knowledge of automobile electricity. It is one of my weakest areas.

Larry,

If the battery never went dead,and the meter is showing discharge when running ,the wires are probably on the wrong side of the meter. Switch the wires and it will show charge when running. If you ran it like that for a year and it never discharged the battery, the meter is wired backwards that all.

Deve,not sure how you have the system wired, but the battery is the real threat in case of short circuit. It is capable of much more than the 150 amps and is not controlled. Most would put a fusible link at the starter and connect wire from there to the ammeter or to the fuse panel, depending on whether an ammeter or volt meter is used. Use of volt meter does not eliminate the concern of a short to ground causing a fire.

That's good advice. This whole thread was started to help people resolve the issue of the correct size Alternator and what can happen if you go over what Chevy designed the system for and then to take it a step further, what to do about it if you have already purchased a bigger Alternator. We have had some great suggestions here! I even got my questions answered about the feasibility of using LED's in the Warning Circuit. Thanks to everyone!

In your case it sounds like they ran a 10gauge wire from the output post of the alternator to the battery rather than through the ammeter.

I did that with mine and took me a little bit to figure why with lights on and heater on the ammeter was showing a discharge while the battery was showing the alternator to be working.

That situation (which I share on my truck), is exactly why a shunt on the back of the ammeter as suggested by Hotrod Lincoln is a better idea than a 10 gauge bypass wire. Hotrod's SS hose clamp mod allows an amount of the overload to go around the ammeter should the ammeter become overloaded. Since the ammeter under normal load, will conduct electricity more readily than the SS hose clamp section, normal ammeter operation will be observed.
Carl

Carl;

I can't find any suggestion from Hotrod Lincoln about a hose clamp bypass. Is that in a different thread or a tech tip?

Search "hose clamp shunt"

How a shunt works: Parallel circuit, same Volts, and, different current. The "Ammeter" is one circuit, and the "accessories" are another. Ammeter, reads current to the battery. Everything else is considered an accessory. Please fuse as required.
Excitation: As much as I like Tommy's metaphor(accurate as it is), excitation refers to the field coils magnetic interaction with the armature coils(magnetic field induces current in the armature). For a "self exciting" alternator, some current in the field coils at startup. Instant on alternator. Our beloved, generators did this with permanent magnets at the field coil, and added current(from the regulator) as required for more load. The regulator inside the alternator works much the same way. Modern cars/trucks, use a lot more electrical energy than our old stuff. Power steering, is now electric boosted. A.C. is standard and sound systems are included. Cigar lighter has been replaced by the USB, charging port and maps(a no load item that used to be free) are now a GPS. Add an electric fuel pump, windows, and, heated seats .....you get the picture.

Yeah, there are good reasons to go to a bigger Alt. I have an actual shunt from Stewart Warner, but there is no way I would put that under the dash. Just the two terminals having all of the Alternators current (Ammeter) is enough for me. Making suggestions and offering solutions to the public is something that is difficult to get right. Every angle and every intelligence level must be considered. Even though it is their choice, offering solutions that can lead to fires or extra expense is something I try to avoid like the plaque. This helps explain why this is a real issue:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

I dunno. Not something I am interested in rolling the dice on, and I am a risk taker compared to most people. If it bothers me, it will bother at least half of the population.

Safe is to find a voltmeter as you know. getting one to fit in the original spot ...that might be tough. All I was attempting to do is explain the "theory" behind the "shunt". Not a recommendation, by any means. The issue only comes up for those that want, or need big current outputs. My truck has the original 2-20 A.C. That is 2 windows down and 20 MPH. An aftermarket radio does live at the bottom of the dash, but it is a small current item and fused. 35 Amps runs every thing I need. Added fuses are to the heater and wiper motor. tTat is about it. For the "hot rod" types, the way to go is the voltmeter, at least it is safe. A main line fuse on the Alternator is wise. There is enough ways to start a fire without adding one, so please be safe.

As usual, good advice Steve. There is a nicely done tech tip on how to convert your stock ammeter gauge to a voltmeter. When I get finished with the Warning Circuit and fine tune the Heater controller, I am going to sit down with a few gauges and do that tech tip. I know they did an amazing job with it. My concern is it is not for the weak. It's a pretty involved and very intricate process. If I can do it, anyone can, so I guess we will see!

http://www.stovebolt.com/techtips/electrical/voltmeter/

If there is ANY way to make it easier, I will find it. I have an Engineer friend who pointed out to me that the original Ammeter is merely a D'Arsonval meter movement and there is no reason we can't just reconfigure the inputs. So I sent him a nice NOS Amp Gauge for our trucks. He looks at it and says, NEVERMIND I WAS WRONG, too much involved.

Bigger project than he wanted to get involved with. Start with a simple system and add stuff until it fails. Not the best way to do things.

When I bought my truck the wiring was a disaster. I put in a high-amp 1-wire alternator and replaced the wiring harness from scratch and life is good. The battery charges, the alternator does its job, the ammeter needle moves around. Room for expansion if I want to add more electrical goodies in the future. The new wiring harness is the way to go. I added a universal fusebox up inside the firewall, too.