Tip & How-To about Chevrolet K3500

How to check your alternator

If you're having problems with the battery in your car staying charged, you may want to test the alternator before spending the money for a new battery. an easy way to do this at home, is to start the car and then remove the negative battery cable. if the car dies then the problem is with the alternator and not the battery.

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99 mercury marquis battery light started coming on so i got a new battery.. also wen its cold its harder to get the car to start n stay started autozone said the alternator tested fine. jus trying to figure out what the problem is so i dnt spend my money on the wrong thing?


While engine is running, wiggle the little wires on the altenator while someone checks to see if light comes on. Hopefully this is the case. these wires break over time due to vibration. The insulation stays connected but the wire inside is broken but still touching, untill they are shook. The plug is about 12 dollars, or you can just splice where it is broken.
The rough idle could be the idle air motor by the throttle. It has two wires and is cylinder shaped. They are about 45 dollars.

Dec 25, 2012 | 1999 Mercury Grand Marquis

1 Answer

Alternator Test? My main fuse blew out and my alternator does not seem top charge. I did a load test and the battery is not charging. Before I spend the shop money, how would I check the alternator to see if it is charging or totally dead? My battery guage on the instrument panel shows about 9 volts and does not move when I increase the RPM's. THANKS.


Check the voltage of the battery with nothing on, it should read 12 volts.
Start the engine and check it again with a few revs. It should read 14 volts.
If it does not then it is not charging. If it does and the battery stays flat, then you have a problem with the battery.

Aug 29, 2011 | 1996 Chevrolet Lumina Mini

2 Answers

new alternator won't charge, battery light flashing.


It sounds pretty "cut-and-dry" to me. You need to have your charging system diagnosed to find the CAUSE of the problem. It is most likely a bad alternator, but I would not spend any money on parts without testing the system first - the alternator could be bad because of a shorted battery cell. Simply replacing the alternator in this case will only destroy a new alternator.

Please also review this article:

What Else Could Be Wrong?

Jun 11, 2011 | Ford Expedition Cars & Trucks

2 Answers

charge light stays on battery and alternater are good


If the red charging light is on, it generally means one of two things: either your alternator is not charging or your battery is too weak and is not charging properly. It also could be a wiring problem in the charging system. The method of testing the charging system is to use an inexpensive alternator tester that clips over the battery cable and indicates positive current. Some of the major auto parts stores have testers available for free loan and may help you with it if you desire to try to fix it yourself. The problem is that the alternator is expensive, so you will want to be sure what the exact problem is before spending money. Inexpensive current/charging testers are available to determine if your alternator's output is sufficient. This should be your first thing to do, which is to determine where the problem is and if its not the alternator, its probably a wiring problem and/or poor battery or corroded battery terminals. It's also possible that your system is charging but there is a current drain somewhere. An in-line current tester connected to the battery will determine if that is the case.

Oct 03, 2009 | 1991 Ford Festiva

1 Answer

possible short, altinator not charging battery


I would say that this may well be a coincidence. The alternator had its own circuitry in it to regulate its output wich, i suspect, is the problem...the good news is that many ap stores can test an alternator on site so you know for sure before spending your money; better yet bring it to a real expert- and auto electric shop- the rebuild alternators and electric motors on site as well as test and diagnose the alternator for you.

Feb 03, 2009 | 1986 Lincoln Town Car

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