Sometimes I think you just like to be contradictory. That's exactly what I wrote. Running the battery down, such as leaving the lights while parked for the day, is not what most people understand as normal every day use. LOL
High voltage
- Thread starter Holy Roller
- Start date
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MomsDuster
Well-Known Member
Ok I'm not one to give tech advice, especially in the electrical world, but I'm going to throw my personal opinion out here just because I can. I realize I'm opening myself up to a beat down but oh well. Here it goes.
1) I am guessing this is a street car.
2) I am guessing this is a mild 383.
As I understand it MSD states 1 amp per 1000rpm. So that leads me to think that with a mild 383 what's the max RPM? 6-7k? And how long does it see that max rpm? A second or two? If this is a street car, in all reality what type of rpm's does the engine spin most of the time? Im guessing idle to 3k. My math says that the majority of the time the MSD will draw 1-3amps and very short durations over that. 60amp should be more than adequate to handle that. And yes I am very aware of the "what if's". These are old cars anything can happen. Me? if I had a 60amp alt and it's already wired, I would wire the MSD per their instructions and go with it.
1) I am guessing this is a street car.
2) I am guessing this is a mild 383.
As I understand it MSD states 1 amp per 1000rpm. So that leads me to think that with a mild 383 what's the max RPM? 6-7k? And how long does it see that max rpm? A second or two? If this is a street car, in all reality what type of rpm's does the engine spin most of the time? Im guessing idle to 3k. My math says that the majority of the time the MSD will draw 1-3amps and very short durations over that. 60amp should be more than adequate to handle that. And yes I am very aware of the "what if's". These are old cars anything can happen. Me? if I had a 60amp alt and it's already wired, I would wire the MSD per their instructions and go with it.
Holy Roller
Well-Known Member
I've had that same link too..lol I looked at alternator from classic industries that was for an early bb that looks like a squareback w/ 2 wires.
pishta
I know I'm right....
^^^
THE EARLY MOPAR (60’S AND 70’S) WIRING AND HOW IT CAN BE UPGRADED
Standard
The Quick and Dirty Charging System Test
Pre 70 wiring
This alternator uses the case to directly provide the ground for the setup. It also has the mechanical style voltage regulator which is usually located near the brake master cylinder.
There are 3 connections on this alternator. The large post is the output as in most alternators. There are also 2 smaller connections. One is labeled "FLD", the other is labeled "GND". The (-) GND is chassis ground, The one marked (+) FLD is the green wire that goes to the voltage regulator and is connected to the "FLD" connection on the voltage regulator. The other side of the voltage regulator is a plug with a dark blue wire for the "IGN" Ignition side.
INSTALL TIP – The only difference between the early single field and later dual field alternators is that one end of the brush holder is grounded to the case. In order to use the later version (Post-70) on early (Pre-70) cars is as simple as adding a short ground wire from the (+) FLD to the case and plug the other in as normal.
Post-70
In 1970 Mopar switched to a transistorized voltage regulator. The unit has a 2 pin connector on it and is usually mounted on the firewall or fender.
There are 3 connections on this alternator also. The large post is the output as usual. There are also 2 smaller connections on this alternator. What is different here is both are labeled "FLD". There is a (-) FLD and a (+) FLD. The (+) FLD dark blue wire is the IGN hot from the key. It also connects to the voltage regulator. The (-) FLD green wire also goes to the voltage regulator. The metal case of the voltage regulator is the GND in this configuration.
How To Do The Conversion
Modified alternator wiring
FIRST – On the original alternator, this brush is grounded to the case of the alternator, so you’ll need to change the alternator to a 1970 or newer style.
NEXT – An additional wire needs to be added to the (+) FLD post on the alternator. This additional (+) FLD wire will now connect to the new voltage regulator. The original green wire that ran to the (+) FLD plug on the original voltage regulator needs to be connected to the wire on the "IGN" side of the original voltage regulator. Effectively eliminating that segment. The origonal dark blue wire will now connect to the voltage regulatr and not chassis ground. That’s it!!!
LAST – One more important step is required, the new voltage regulator base must have a good ground to its mounting surface. If there isn’t a good ground to the new voltage regulator case, the charging system will not work.
If you are converting to a late Chrysler electronic ignition from a points style ignition this is a must do. The cost for the solid state version is minor. And the reliability takes a quantum leap.
There are sources for upgrade harnesses if you don’t think you are comfortable with the electrical stuff.
Reference Reading – MyMopar.com
THE EARLY MOPAR (60’S AND 70’S) WIRING AND HOW IT CAN BE UPGRADED
Standard
The Quick and Dirty Charging System Test
- Remove the (+) FLD wire from the alternator.
- Put a temporary jumper wire from the same (+) FLD terminal to the large output post on the alternator (battery +).
- Start the car and see if it charges. If it does… good alternator. If not … bad alternator. If it did charge, then the voltage regulator is the problem child.
- Turn the ignition key to the on position. Check for power on the small IGN terminal of the regulator. If there is, then see if there is any power on the other voltage regulator post to the alternator. A bad ground on the voltage regulator case is a very common problem. If not then you need to chase down the IGN power issue.
Pre 70 wiring
This alternator uses the case to directly provide the ground for the setup. It also has the mechanical style voltage regulator which is usually located near the brake master cylinder.
There are 3 connections on this alternator. The large post is the output as in most alternators. There are also 2 smaller connections. One is labeled "FLD", the other is labeled "GND". The (-) GND is chassis ground, The one marked (+) FLD is the green wire that goes to the voltage regulator and is connected to the "FLD" connection on the voltage regulator. The other side of the voltage regulator is a plug with a dark blue wire for the "IGN" Ignition side.
Post-70
In 1970 Mopar switched to a transistorized voltage regulator. The unit has a 2 pin connector on it and is usually mounted on the firewall or fender.
There are 3 connections on this alternator also. The large post is the output as usual. There are also 2 smaller connections on this alternator. What is different here is both are labeled "FLD". There is a (-) FLD and a (+) FLD. The (+) FLD dark blue wire is the IGN hot from the key. It also connects to the voltage regulator. The (-) FLD green wire also goes to the voltage regulator. The metal case of the voltage regulator is the GND in this configuration.
How To Do The Conversion
Modified alternator wiring
FIRST – On the original alternator, this brush is grounded to the case of the alternator, so you’ll need to change the alternator to a 1970 or newer style.
NEXT – An additional wire needs to be added to the (+) FLD post on the alternator. This additional (+) FLD wire will now connect to the new voltage regulator. The original green wire that ran to the (+) FLD plug on the original voltage regulator needs to be connected to the wire on the "IGN" side of the original voltage regulator. Effectively eliminating that segment. The origonal dark blue wire will now connect to the voltage regulatr and not chassis ground. That’s it!!!
LAST – One more important step is required, the new voltage regulator base must have a good ground to its mounting surface. If there isn’t a good ground to the new voltage regulator case, the charging system will not work.
If you are converting to a late Chrysler electronic ignition from a points style ignition this is a must do. The cost for the solid state version is minor. And the reliability takes a quantum leap.
There are sources for upgrade harnesses if you don’t think you are comfortable with the electrical stuff.
Reference Reading – MyMopar.com
Holy Roller
Well-Known Member
Thank you pishta as well as everyone for all the info. I think I'm going to use the 60a squareback. From what I've read, it should do the job.^^^
THE EARLY MOPAR (60’S AND 70’S) WIRING AND HOW IT CAN BE UPGRADED
Standard
The Quick and Dirty Charging System Test
Pre-1970
- Remove the (+) FLD wire from the alternator.
- Put a temporary jumper wire from the same (+) FLD terminal to the large output post on the alternator (battery +).
- Start the car and see if it charges. If it does… good alternator. If not … bad alternator. If it did charge, then the voltage regulator is the problem child.
- Turn the ignition key to the on position. Check for power on the small IGN terminal of the regulator. If there is, then see if there is any power on the other voltage regulator post to the alternator. A bad ground on the voltage regulator case is a very common problem. If not then you need to chase down the IGN power issue.
View attachment 1715250012
Pre 70 wiring
This alternator uses the case to directly provide the ground for the setup. It also has the mechanical style voltage regulator which is usually located near the brake master cylinder.
There are 3 connections on this alternator. The large post is the output as in most alternators. There are also 2 smaller connections. One is labeled "FLD", the other is labeled "GND". The (-) GND is chassis ground, The one marked (+) FLD is the green wire that goes to the voltage regulator and is connected to the "FLD" connection on the voltage regulator. The other side of the voltage regulator is a plug with a dark blue wire for the "IGN" Ignition side.
View attachment 1715250013INSTALL TIP – The only difference between the early single field and later dual field alternators is that one end of the brush holder is grounded to the case. In order to use the later version (Post-70) on early (Pre-70) cars is as simple as adding a short ground wire from the (+) FLD to the case and plug the other in as normal.
Post-70
In 1970 Mopar switched to a transistorized voltage regulator. The unit has a 2 pin connector on it and is usually mounted on the firewall or fender.
There are 3 connections on this alternator also. The large post is the output as usual. There are also 2 smaller connections on this alternator. What is different here is both are labeled "FLD". There is a (-) FLD and a (+) FLD. The (+) FLD dark blue wire is the IGN hot from the key. It also connects to the voltage regulator. The (-) FLD green wire also goes to the voltage regulator. The metal case of the voltage regulator is the GND in this configuration.
How To Do The Conversion
View attachment 1715250014
Modified alternator wiring
FIRST – On the original alternator, this brush is grounded to the case of the alternator, so you’ll need to change the alternator to a 1970 or newer style.
NEXT – An additional wire needs to be added to the (+) FLD post on the alternator. This additional (+) FLD wire will now connect to the new voltage regulator. The original green wire that ran to the (+) FLD plug on the original voltage regulator needs to be connected to the wire on the "IGN" side of the original voltage regulator. Effectively eliminating that segment. The origonal dark blue wire will now connect to the voltage regulatr and not chassis ground. That’s it!!!
LAST – One more important step is required, the new voltage regulator base must have a good ground to its mounting surface. If there isn’t a good ground to the new voltage regulator case, the charging system will not work.
If you are converting to a late Chrysler electronic ignition from a points style ignition this is a must do. The cost for the solid state version is minor. And the reliability takes a quantum leap.
There are sources for upgrade harnesses if you don’t think you are comfortable with the electrical stuff.
Reference Reading – MyMopar.com
Let’s not forget that heat has a huge piece of the puzzle for alternator output. A lot of alternators sold that are chrysler housings but wound differently or have a higher output voltage regulator (internally not externally) once they get hot, output is diminished. There is a reason big truck alternators have a frame size 3 times larger than the alternators we deal with on cars even though output is only 110amps. They handle the heat of 110amps better and designed that way. So if you go to “bobo zone” and get their “93amp” round back alternator for an extra $15 than the stock 37amp... how long will it last?
My thought is of you are needing a high amp alternator, you need to redesign your system for that (or around) that alternator. You may or may not get away with not doing that. But is melting down your car worth not taking a few hours worth of work to make it right? Also, if you are worrying about judges at concourse de’elegamce..... I’m sure you don’t have a kicking stereo or electric fan. Trailer your ride at night and possibly don’t even start your car- just push it around.
Just my 2 cents.
My thought is of you are needing a high amp alternator, you need to redesign your system for that (or around) that alternator. You may or may not get away with not doing that. But is melting down your car worth not taking a few hours worth of work to make it right? Also, if you are worrying about judges at concourse de’elegamce..... I’m sure you don’t have a kicking stereo or electric fan. Trailer your ride at night and possibly don’t even start your car- just push it around.
Just my 2 cents.
Good points about heat, but to evaluate whether any given unit is going to run hotter, the electric load is the driving force.
Yes the higher rated alternator may run hotter if both are being run at maximum for 100% of the time (duty cycle) and it doesn't have better heat sinks and cooling capacity.
Fortunately, thats not usually the situation.
Lets look at some typical situations.
Take two round back alternators but one has the rotor-stator combo for 37 amps, and the other 60 amps (rated).
a. Lets say normal driving is daytime and good weather.
Constant electric load is roughly 2 amps for ignition, 1-2amps for field. Total constant load 3 to 4 amps.
Temporary additional loads are:
Recharging after start. 15 amps initially, then within 1 minute 5 amps, then 2 amps for 2-5 minutes diminishing to zero.
Turn signal. 2.5 amps for less than 1 minute at a time.
Brake lights. 2.5 amps for less than 1 minute at a time.
Therefore temporary additional draws on the alternator will be 15 amps or less for very short periods of time.
Whichever alternator is used may put out 20 to 25 amps for less than a minute, and 5 to 7 amps also for less than a minute at a time.
Its hard to be certain which will handle it more easily for the reasons mentioned (by Syleng1).
Since the alternators are only being asked to provide 3 -4 amps for 95% or more of the driving, it doesnt matter much. Both will have plenty of time to cool down.
b. Lets say the car will be used for driving all night in a cold rain.
Constant Electric load is roughly 2 amps for ignition, 2 for field, 12 for headlights and tail lights, 6 for wipers on high, 7 for fan on high.
> Total Constant Load of 30 amps.
Temporary additional loads are same as in scenario above (a).
At normal driving speeds, my bet is the 60 amp alternator would be less stressed than the 37 amp.
A heavier, wider, or better cooled alternator like a squareback 60 amp would almost certainly be less stressed and run cooler than the either of the roundbacks.
At very low driving speeds, such as crawling in traffic, often stopped, the 37 amp roundback can't provide the 30 plus amps at 14 Volts. As system voltage drops below 13, the battery starts to provide power instead of the alternator. The more frequently the battery has to provide power, the more frequently it will needed recharging. This results in higher demand on the alternator when engine speed increases. This is one type of scenario where the standard lower rated alternators are not a good choice. It not only stresses the alternator, but sometimes also the charging circuit.
Yes the higher rated alternator may run hotter if both are being run at maximum for 100% of the time (duty cycle) and it doesn't have better heat sinks and cooling capacity.
Fortunately, thats not usually the situation.
Lets look at some typical situations.
Take two round back alternators but one has the rotor-stator combo for 37 amps, and the other 60 amps (rated).
a. Lets say normal driving is daytime and good weather.
Constant electric load is roughly 2 amps for ignition, 1-2amps for field. Total constant load 3 to 4 amps.
Temporary additional loads are:
Recharging after start. 15 amps initially, then within 1 minute 5 amps, then 2 amps for 2-5 minutes diminishing to zero.
Turn signal. 2.5 amps for less than 1 minute at a time.
Brake lights. 2.5 amps for less than 1 minute at a time.
Therefore temporary additional draws on the alternator will be 15 amps or less for very short periods of time.
Whichever alternator is used may put out 20 to 25 amps for less than a minute, and 5 to 7 amps also for less than a minute at a time.
Its hard to be certain which will handle it more easily for the reasons mentioned (by Syleng1).
Since the alternators are only being asked to provide 3 -4 amps for 95% or more of the driving, it doesnt matter much. Both will have plenty of time to cool down.
b. Lets say the car will be used for driving all night in a cold rain.
Constant Electric load is roughly 2 amps for ignition, 2 for field, 12 for headlights and tail lights, 6 for wipers on high, 7 for fan on high.
> Total Constant Load of 30 amps.
Temporary additional loads are same as in scenario above (a).
At normal driving speeds, my bet is the 60 amp alternator would be less stressed than the 37 amp.
A heavier, wider, or better cooled alternator like a squareback 60 amp would almost certainly be less stressed and run cooler than the either of the roundbacks.
At very low driving speeds, such as crawling in traffic, often stopped, the 37 amp roundback can't provide the 30 plus amps at 14 Volts. As system voltage drops below 13, the battery starts to provide power instead of the alternator. The more frequently the battery has to provide power, the more frequently it will needed recharging. This results in higher demand on the alternator when engine speed increases. This is one type of scenario where the standard lower rated alternators are not a good choice. It not only stresses the alternator, but sometimes also the charging circuit.
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Thank you for acknowledging the heat load. And although you are correct with what is actually going on with alternator load requirements. And “yes” tractor trailers have a high usage load - upwards of 70amps with just amp load on lighting alone. but so much runs on the air system which lessens the electrical load.
Anyhow, I believe your correct BUT the reason we are chatting about the loads is because as we add electrical loads - in this case ignition, plus a big block in an abody... we are adding electrical fans, custom ignition, plus we all dislike dim head lamps, want more sounds to include power amps for the music and even in some cases adding ac, power locks and power windows, power seats, etc. So not to get off track with the original post about alternator usage and how upgrading the alternator is only part of the equation.
Also, please check your math as those amp loads you stated in the Mattax post above is not correct. Brake lamps are listed as 2.5 amps and so is turn signals. If a turn signal is 2.5amps then brakes lamps is 5amps (actually closer to 6amps due to they are run in series and heat loss across the wire. Also, night time driving includes running lamps all the way around, dash lamps center console lamps, aux gauges and lighting possibly other lighting the load can be upwards of 30+amps alone.
I appoligiese in advance for my detail but I was a Master Tech for GM in my earlier days and my specialties was automatic transmissions and electrical. Amp loads were calculated down to the 10th of an amp on cars because of weight and components (weight of over sized wiring or parts translated into fuel mileage and cost of building production cars. Smaller wire was a $0.02 per harness but across 100,000 vehicles was a big savings.) smaller alternators was also a fuel savings. Etc, etc.
All I will add is you need to look at your individual needs and decide what is best for your car. Stock /6 with all stock electrical keep it stock. Built street car needs more power and modified electrics and modified electrical needs.
Okay- I’m done. Off soap box.
You're right.
Four 1034 lamps have nominal draw of 2.36 amps.
Four 158 instrument panel lights have a nominal draw of 0.96 amps
So total for headlight and tail lights will be closer to 3.38 amps. That includes the front markers and the instrument panel, but not sidemarkers of a '68 or '70 up Abody.
Likewise, a pair of 1034 brake lamps have a nominal draw of 3.6 amps.
I really didn't think it was neccessary or useful to get into this level of detail for example scenarios. In fact I prefered nice round numbers so folks could easily follow along.
There was no consideration here for any alterations to the basic load required to run an engine. The difference in electric power demand of a v-8 vs slant six ignition isnt enough to even bring up for what we're talking about.
Four 1034 lamps have nominal draw of 2.36 amps.
Four 158 instrument panel lights have a nominal draw of 0.96 amps
So total for headlight and tail lights will be closer to 3.38 amps. That includes the front markers and the instrument panel, but not sidemarkers of a '68 or '70 up Abody.
Likewise, a pair of 1034 brake lamps have a nominal draw of 3.6 amps.
I really didn't think it was neccessary or useful to get into this level of detail for example scenarios. In fact I prefered nice round numbers so folks could easily follow along.
There was no consideration here for any alterations to the basic load required to run an engine. The difference in electric power demand of a v-8 vs slant six ignition isnt enough to even bring up for what we're talking about.
fxrtharley
Member
If anyone is still on this thread, the only question I have is: I have two blue wires going to my original alternator, one would eb ignition but what is the other and I assume when converting to solid state regulator I would tie both of these blue wires into my new jumper back to the alternator? Thanks
Start a new thread. Explain what year car, what's been done to the wiring (if you don't know, post photos), and what the problem or goal is.
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