02-25-2011, 07:14 AM | #1 |
Senior Member
Join Date: Jun 2010
Location: Queens, NYC
Posts: 212
|
Alternators
What are some tips/suggestions for trouble shooting/diagnosing alternator issues by the Barn crew?
|
02-25-2011, 07:54 AM | #2 |
Senior Member
|
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 |
Sponsored Links (Register now to hide all advertisements) |
|
02-25-2011, 08:00 AM | #3 |
Senior Member
|
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 |
02-25-2011, 12:48 PM | #4 |
Senior Member
Join Date: May 2010
Location: Kalamazoo
Posts: 1,656
|
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 |
02-25-2011, 01:09 PM | #5 |
Senior Member
Join Date: May 2010
Location: Santa Rosa, CA
Posts: 1,276
|
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.
|
02-25-2011, 01:37 PM | #6 |
Senior Member
Join Date: May 2010
Location: Sugar Land, TX
Posts: 4,393
|
Re: Alternators
Sponsored Links (Register now to hide all advertisements)
|
02-25-2011, 02:06 PM | #7 |
Senior Member
Join Date: May 2010
Location: Rhode Island
Posts: 1,868
|
Re: Alternators
|
02-26-2011, 10:24 AM | #8 |
Senior Member
Join Date: Jun 2010
Location: Queens, NYC
Posts: 212
|
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 |
02-26-2011, 06:30 PM | #9 |
Senior Member
Join Date: May 2010
Location: Concord CA
Posts: 623
|
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 |
02-26-2011, 07:01 PM | #10 | |
Senior Member
Join Date: May 2010
Location: Kaukauna, Wisconsin
Posts: 392
|
Re: Alternators
Quote:
|
|
02-27-2011, 01:53 PM | #11 |
Senior Member
Join Date: May 2010
Location: Rhode Island
Posts: 1,868
|
Re: Alternators
|
Thread Tools | |
Display Modes | |
|
|
Sponsored Links (Register now to hide all advertisements) |
|