Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 02-25-2011, 07:14 AM   #1
cars56
Senior Member
 
Join Date: Jun 2010
Location: Queens, NYC
Posts: 212
Default Alternators

What are some tips/suggestions for trouble shooting/diagnosing alternator issues by the Barn crew?
cars56 is offline   Reply With Quote
Old 02-25-2011, 07:54 AM   #2
Mike V. Florida
Senior Member
 
Mike V. Florida's Avatar
 
Join Date: May 2010
Location: South Florida
Posts: 14,054
Send a message via AIM to Mike V. Florida
Default Re: Alternators

What are the symptoms?
__________________
What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II
Mike V. Florida is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 02-25-2011, 08:00 AM   #3
Mike V. Florida
Senior Member
 
Mike V. Florida's Avatar
 
Join Date: May 2010
Location: South Florida
Posts: 14,054
Send a message via AIM to Mike V. Florida
Default Re: Alternators

A simple tool for troubleshooting car problems with an alternator is a voltage-ohm-meter. This is not a special, scientific, meter that requires a doctorate degree to operate and understand. One usually only costs $5 to $10 dollars at any auto parts or department store. The meter should be capable of reading AC and DC voltage and ohms (resistance).
Place the meter selector switch in the DC voltage mode. Place the red lead onto the positive battery terminal, and the negative lead onto the negative battery terminal. Read the battery voltage on the meter with the car engine off. The ideal voltage is between 12 and 13.5 volts. If the voltage is less than 11 volts, try to charge the battery with a battery charger to bring the voltage up to the ideal range and continue the test. If unable to charge the battery fully, then the battery is the suspect. The next phase of the test will help to verify if this is true.
While holding the meter leads onto their respective battery posts, have an assistant start the car and allow it to idle. The voltage should now read closer to 14 to 14.5 volts at the meter. If it does, this indicates the alternator is supplying current to both the battery and to the car’s electrical system. If there is no change in the voltage reading with the car running, the alternator may be bad.
Final Alternator Troubleshooting Check

A more precise step to verify if the alternator is supplying power to the car battery and electrical system is with the use of an ampere probe. While this meter is not as inexpensive as the volt-ohm-meter, one can be borrowed or rented from most national parts stores.
The meter clamps around a single power lead to detect the amount of current, not voltage, flowing through the wire. Clamp an ohm-meter onto the positive lead from the alternator and repeat the steps used before.
Start the car and read the amp meter readout for current flow. If no flow is detected, make sure that the meter is clamped onto only one wire, and that it is the positive, or red, wire leading from the alternator to the battery. The detection of 3 to 4 amps on the meter is a sign the alternator is working, and the battery is suspect. If no amperage is visible on the meter, remove or replace the alternator.
While an automotive alternator can be faulty and not fail entirely, it usually either works or it doesn’t. An alternator that works intermittently is much harder to isolate, even for a professional with advanced tools. However, the alternator problems troubleshooting steps discussed here are effective at isolating a complete alternator failure.


__________________
What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II
Mike V. Florida is offline   Reply With Quote
Old 02-25-2011, 12:48 PM   #4
steve s
Senior Member
 
steve s's Avatar
 
Join Date: May 2010
Location: Kalamazoo
Posts: 1,656
Default Re: Alternators

I've heard that the end of the alternator shaft opposite the pulley becomes very magnetic if the alternator is working. The tip of a large screw driver should be pulled strongly to it.


Mike, is this true?

Steve
steve s is offline   Reply With Quote
Old 02-25-2011, 01:09 PM   #5
PC/SR
Senior Member
 
Join Date: May 2010
Location: Santa Rosa, CA
Posts: 1,276
Default Re: Alternators

Mike V's tips are good ones. Just remember that some alternators have to be revved up before they start charging. Once they start, they will charge at idle.
PC/SR is offline   Reply With Quote
Old 02-25-2011, 01:37 PM   #6
mrtexas
Senior Member
 
mrtexas's Avatar
 
Join Date: May 2010
Location: Sugar Land, TX
Posts: 4,393
Default Re: Alternators

Sponsored Links (Register now to hide all advertisements)
One other consideration. If the one wire alternator has been sitting for a long time without use the field can lose it's charge and won't work. I bought a good nurex alt for $25 because "it wouldn't work". I scratched somewhere(can't remember but I'm sure someone here can tell you) on it with the battery and it started to work.
mrtexas is offline   Reply With Quote
Old 02-25-2011, 02:06 PM   #7
RonC
Senior Member
 
RonC's Avatar
 
Join Date: May 2010
Location: Rhode Island
Posts: 1,868
Default Re: Alternators

You can make your own 6 Volt Positve Ground Alternator.

https://www.youtube.com/watch?v=JMl-4VQBFOQ
RonC is offline   Reply With Quote
Old 02-26-2011, 10:24 AM   #8
cars56
Senior Member
 
Join Date: Jun 2010
Location: Queens, NYC
Posts: 212
Default Re: Alternators

Alot less has been written on alternator trouble shooting vs generators as can be expected.
Thanks to everyone and future posters in advance for sharing your expertise on the topic.
Cars56
30 coupe, NYC
cars56 is offline   Reply With Quote
Old 02-26-2011, 06:30 PM   #9
Herb Concord Ca
Senior Member
 
Join Date: May 2010
Location: Concord CA
Posts: 623
Default Re: Alternators

If you have a VOM and know how to use it, a quick check to make with the motor off, disconnect the wires attached to the alternator, and measure the resistance from that post to ground. If you get any reading, you have a diode in the the alternator that is leaking, and if left connected for a few days will discharge your battery.
I always remove my safety fuse by the starter, to prevent this, if the car is going to set for a few days, overnite is OK.
My alternator has a leakage resistance of about 1200 ohms.
Regards,
herb
Herb Concord Ca is offline   Reply With Quote
Old 02-26-2011, 07:01 PM   #10
Don/WI
Senior Member
 
Join Date: May 2010
Location: Kaukauna, Wisconsin
Posts: 392
Default Re: Alternators

Quote:
Originally Posted by RonC View Post
You can make your own 6 Volt Positve Ground Alternator.

https://www.youtube.com/watch?v=JMl-4VQBFOQ
Thanks, RonC for the link to this article on the 6 Volt Positive Ground Alternator. I'm sure this will be used by a few of us Ford Barners. Don/WI
Don/WI is offline   Reply With Quote
Old 02-27-2011, 01:53 PM   #11
RonC
Senior Member
 
RonC's Avatar
 
Join Date: May 2010
Location: Rhode Island
Posts: 1,868
Default Re: Alternators

Model A Alternator Test

https://www.youtube.com/user/alternat...18/YATOGp-lvWk
RonC is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 07:42 AM.