What makes a 140 amp Alternator different? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 07-10-2005, 07:52 PM
1982 SS's Avatar
Flamethrower
 

Last journal entry: More Cooling fan pictures.
Last photo:
Join Date: Mar 2005
Location: Utah
Age: 27
Posts: 340
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
What makes a 140 amp Alternator different?

What I have now is an GM 3 wire internally regulated Alternator with a "94" amp casting mark and it won't keep up with my car. First off, I have a holley electric fuel pump a dual cooling fan set-up and no radio. I have noticed my voltage (as read on the factory guage) is around the 10 volt range (marked at 8 13 and 18 volts so I'm guessing) at idle and picks up to a little over 13 when I get moving but the alternator seems loaded as the belt squeaks (it's tight, I've checked) when I lean into it a little. Now it gets worse, At night, lights on fans on and fuel pump on, I never get above the 10-10.5 volt range and it seems to be really loaded (squeaky most of the time). If this really is a 94 amp job, I would think it would keep up better than it does. I did rebuild it and checked the parts that went in before I put it in the car. It seems to be a heavier alternator when compared to a 72 and 63 I have on the bench, the windings are much larger and there are more of them on the 94. I did check the voltage from the lug on the back to the positive side of the battery and got .68 volts (which I was told is accepteable as most of the power is going through the wire to the battery) anything else I should check before I shell out for a larger alternator?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-11-2005, 08:30 AM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Confused..

Doc here,

Your post is very confusing...

If the belt is slipping then the Alternator is NOT tight, out of line, OR your suffering rotor lock..(Dead Short Across the windings, or mechanical lockup)

You Should read 14.4 volts at he battery at all times across the battery...whenever the vehicle is running with one exception..Total load consumption..(EVERYTHING in the car ON and running max..) And then It should never go below 13.75 volts..and it SHOULD never do excursions at any speed.

If it does, the regulator is bad, or the diode pack is shot (especially in the case of 10 volt readings..) Rebuild or replace.

If you upgrade the alternator to nearly double amperage, you have to consider the need to upgrade the belt pulley system..a small thin belt may not be able to drive the load on the alternator without slipping or breaking.

I see no need to replace the bad one you have now with a lager one, since the 60-70 amp should work just fine.

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-11-2005, 10:36 AM
1982 SS's Avatar
Flamethrower
 

Last journal entry: More Cooling fan pictures.
Last photo:
Join Date: Mar 2005
Location: Utah
Age: 27
Posts: 340
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sorry about the confusion, i didn't quite know how to put all the information is down. I have already gone through the alternator once when I got it (it was in a pile of parts I got awhile ago).

Given the 10 volt readings and moving up to normal as the engine speed increases, the diodes or regulator could be bad. I had a previous alternator go bad and only put out 10 volts but it didn't move around like this one does. Turned out that one was a diode. Will almost any rebuild kit work or do I need one for the 94 amp one?

You mentioned "rotor lock", how does that affect the output of the alternator?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-11-2005, 09:18 PM
1982 SS's Avatar
Flamethrower
 

Last journal entry: More Cooling fan pictures.
Last photo:
Join Date: Mar 2005
Location: Utah
Age: 27
Posts: 340
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Okay, I have more information.

I swapped out the 94 amp alternator for a 72 that I had on the bench. The 72 does keep up with the car and the fans which leads me to believe the diodes (on the 94) may not be working properly/burned out.

However, when I load my 72 (fans, fuel pump, lights), mechanically it becomes harder to turn (as it should) but it gets hard enough to glaze the belt. As docvette said I would have to step up the ability to turn the alternator. How can I get around this? I could underdrive the pulley or get more belt surface to touch it but how do I do that?

Also, it since I did not glaze the belt with the 94, is it possible that larger alternators take less mechanical energy to create the same output as a smaller alternator? Just thinking out loud here.

Thanks for your input on this, guys.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 07-11-2005, 10:06 PM
USAF F-16 ELECTRICIAN
 
Join Date: Sep 2004
Location: utah
Age: 30
Posts: 140
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
do you have a large load, no alternaor should be like that. i had a 100 amp on my 1985 olds 98 and it had no problem and i had a 1500 watt amp. or just try changing the belts maybe they are just too worn out. and there is almost no way that lights fans and electric fuel pump take that much power. 70 amps at 14 volts is 980 watts. thats is A LOT of power.

Last edited by 455c-10; 07-11-2005 at 10:15 PM.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 07-12-2005, 03:31 AM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Alternator

Doc here,

Plain and simple.....

YOU HAVE A BAD ALTERNATOR......REPLACE IT!

If you can turn it under any load...it's shot.....61 + amps =746 watts at 12 volts...746 watts = 1 Horsepower..you got that much in your grip...?????

2 Fans alone is more than 746 watts.....

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 07-12-2005, 03:36 AM
USAF F-16 ELECTRICIAN
 
Join Date: Sep 2004
Location: utah
Age: 30
Posts: 140
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
hey doc how much power would those fans take to run? startup would be greater than that but once they are running it shouldnt be that much is it?
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 07-12-2005, 03:53 AM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Power

Doc here,

Depends on the fans, I use a rule of thumb, min..30 amps...start up, free wheel, and rotor lock..anything higher should blow a link...to be safe ..

If you really want exact figures, get your Volt/ohm meter out and measure voltage /current, in it's extreme, than apply a little ohms law..

Or ballpark it 2 fans..1/2 hp...freewheel, =total draw 746 watts...1 hp...approx 65 amps...total draw.

Rotor locks will go as high as 600 amps should you allow them to occur..(no link protection) over sized wire, no relays..ect...

Oh, How do you get a rotor lock? Suck a K~Mart bag into the fan and let it wind up tight...so the rotating elements can no longer move, or lose and freeze up a bearing...just for a few...

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 07-12-2005, 04:00 AM
USAF F-16 ELECTRICIAN
 
Join Date: Sep 2004
Location: utah
Age: 30
Posts: 140
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
guess i need to get back into the real electronics...its been a while. the stuff i do on the jets out here is kind of a joke. i forgot all the stuff i learned about the real stuff...mosfet ttl cmos...electric motors werent my strong point in school too many variables. and i havent found any good books on the stuff. all mine were stolen out of the back of my friends truck.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 07-12-2005, 05:10 PM
1982 SS's Avatar
Flamethrower
 

Last journal entry: More Cooling fan pictures.
Last photo:
Join Date: Mar 2005
Location: Utah
Age: 27
Posts: 340
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Goody, guess I need to spend more money... Oh well, I've done it before.

The fans pull something like 40 amps on startup and drop to less than 30 combined for continuous running.

I did try the belt with a new one and the same thing happens. It slips and starts to smoke the belt.

What type should I look for to be the most useful? A good slightly higher amperage one (I think stock is a 70) maybe in the 80's or just get a new stock size one, or do I rebuild one (94 or 72...again) I already have. Since nobody's system is smart enough anymore to get parts based on casting numbers would a 70 amp or a 100 amp (either/or) rebuild kit work?

Where would I get a good quality rebuild kit anyway? I can go to NAPA or CarQuest to avoid the Niehoff and Autocraft parts I have used in the 94 amp one.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 07-16-2005, 11:07 PM
1982 SS's Avatar
Flamethrower
 

Last journal entry: More Cooling fan pictures.
Last photo:
Join Date: Mar 2005
Location: Utah
Age: 27
Posts: 340
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Well, I solved the problem. I used the age old Proverb, throw enough money at it and it will eventually go away. And away it went, but not all at once.

I figured that my current luck with rebuilding my alternators was so great (they sort of worked as the above posts read), I just bought a 140 Amp alternator through Summit. That solved part of the problem. I now had an alternator that was capable of keeping up.

I still had a problem with griping the pulley. Three belts later, I still couldn't generate enough grip. I was at My local Checker store and asked one of the most knowledgeable there and he said he had a pile of pulleys behind the counter. I was looking through and found two pulley that measure 2.93". I figured that if the pulley on my 140 was smaller I could just swap. I get home and measure the pulley on the 140 installed in the car. It measured 2.3". With over .5" more diameter, it comes out to about 25% more pulley circumference. And the shaft diameter was the same too. All I needed was a pulley that was a little larger on the 140 and It now goes and keeps up real well.

On this rather expensive journey, I discovered that there really are not a lot of pulleys in the 25- 40% underdriven range. I found some 5" but not the 3"-3.25" diameter I was looking for. Basically a slightly underdriven pulley worked out great in the end.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 07-17-2005, 11:00 PM
1982 SS's Avatar
Flamethrower
 

Last journal entry: More Cooling fan pictures.
Last photo:
Join Date: Mar 2005
Location: Utah
Age: 27
Posts: 340
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Well one more update on te alternator thing. The 2.9 pulley is a large improvement over the 2.3, but a little more pulley would still be nice. Like I mentioned, something about 3.25" in diameter would be real nice. Luckily, I am taking a course in machining and I will be able to make one in a short time. In the meantime, I will have to settler for the 5" and live with it for awhile. At least I will be able to drive the car normally without throwing a belt.
Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pro Topline Heads surfinca Engine 33 12-28-2008 12:37 PM
will a 18 circuit GM universal Painless setup handle a 140 amp alt? rick458 Electrical 3 02-27-2005 03:57 PM
100 AMP Service In Garage Help daveh Garage - Tools 9 02-27-2005 02:15 AM
NEED HELP! Amp is not getting power Meka Electrical 2 07-10-2004 06:15 PM
High Amp Alternator 84layinframe Electrical 3 04-25-2004 05:00 PM


All times are GMT -6. The time now is 08:57 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.