On my 2002 Silverado with the 5.3 liter engine. My battery light occasionally comes on and off. Generally on local highways. Once on the freeway it stays off. It has done this twice in the last few months then much more yesterday driving around town. I stopped at an auto parts place my friend works at. They put there tester on it and it says all is OK. 97 amps from the alternator. Diodes are OK. Battery showed good. Battery is still original. The guy that did the test said the tester is not always 100% accurate. I am thinking I should put in a new battery since mine is 6 years old now and I will need a new one sooner or later anyway. Any suggestions? I hate to replace the alternator just too "see" if it fixes my problem.

Thanks
Rodney

When the "battery" light comes on, what is the voltmeter doing?

If it's still showing a charge (right of center) it ought to be okay.
If it's showing a discharge (left of center) it probably means that there is an alternator problem. (Or that something is severely loading the electrical system, or sucking down the idle speed.)
See if the battery light coming on coincides with the A/C compressor cycling on.
Of course, check all the connections.

If the truck can sit for an extended period, and still start without "dragging", the battery is ok.

quote Originally posted by Raydar: When the "battery" light comes on, what is the voltmeter doing? If it's still showing a charge (right of center) it ought to be okay. If it's showing a discharge (left of center) it probably means that there is an alternator problem. (Or that something is severely loading the electrical system, or sucking down the idle speed.) See if the battery light coming on coincides with the A/C compressor cycling on. Of course, check all the connections. If the truck can sit for an extended period, and still start without "dragging", the battery is ok.

Volt meter is staying to the right of center all the time. Stays constant as the battery light comes on. This is a digital message center display. Not the older idiot light type. Starts no problem. I know the feeling of a battery on its last gasps. Battery seems OK yet although it is 6 years old.

Rodney

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Rodney Dickman

Fiero Parts And Acc's Web Page:
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My 2001 Silverado has been doing the same thing sporadically for a couple months. Still haven't found anything wrong.

Battery likely won't fix it. I suspect if it was the battery, you'd get a light under more conditions than you are. One thing to do is find a place with one of the computerized battery testers. These do allot more than typical load tests. (They can also test severely discharged batteries and tell you if they are bad before you try to charge them and maybe have it explode in your face.)

1. Check for recalls. Make sure any are done or get them done. GM has a ton of truck recalls. Many of them for electrical problems.

2. Check the wiring VERY carefully. If there is damaged/failing wiring, it can make the alternator shut off intermittently.

3. Replace the belt and the tensioner if it has one. If either are letting things slip, the alt light can come on. (This is possible for several reasons. More in a sec.) You have enough years and probably miles that the tensioner can be weak/sticking. Use a Dayco Polycog or Gates belt.

4. Find out exactly which type of alternator and what regulator is in it.

GM changed to what is called an ASR a number of years ago. Short for Application Specific Regulator. (Yes, I thought it was a dumb sh_t name too.) The ASR is often tied much tighter to the ECM/PCM than the ones used in past SI or CS alternators ever were. To the point that the PCM actually turns the alternator on/off. If the PCM or wiring to it have problems then the alternator signal could actually be false. Meaning the alt may be shutting off but there's not a damn thing wrong with it.

If the parts books don't say... look at the wiring charts. A typical CS is wired as shown in my cave with 2 or three wires. Ones that are tied to the PCM can use similar wiring, use the 4th wire and maybe more. You're looking for any of the side terminals going to the ECM/PCM. If it uses 4 or more wires on the side, then it is pretty certain to be tied to the PCM. (A CS alternator using the P terminal is connected to the PCM. No other reason to use it that way.)

Belts are even more important with ASR, or even standard CS family alternators, when wired to feed the Tach (P terminal) signal to the PCM. If the belt slips then the alternator may be on but not in the speed range expected by the computer. The computer may then turn on the Alt/Bat lamp, or shut off the alternator (Which should turn on the lamp), depending on programming and wiring.

Another possible test... if the alternator is connected to the PCM... see if there are any codes stored. A PCM controlling the alt may not have turned on the MIL lamp when setting a code for this sort of problem since the Alt/Bat light is on.

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Talked to a friend of mine that is a GM dealer tech. HE said it may be the cluster. They have a replacement system. They exchange them with a reworked unit. About $300 or so plus labor. He said wiggle the wires to the alternator. I did that while they were testing it at the auto parts place. Did not change anything. But after talking to him I went out and removed the plug to look for corrosion. I found none but after I put the plug back in and started it up the battery light came on for several seconds than went off. I went for a dive and it did not coma back on. Maybe the plug is making a marginal connection. I'll see in the coming days if it is OK. If not I'll take the plug back out and try to distort the connectors slightly to get a better connection. If not I can try installing a replacement connector. It is raining today. Not sure if that is making a difference also.

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Rodney Dickman

Fiero Parts And Acc's Web Page:
www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

Most of those are Metripack Pull to Seat terminals. The only way to fix them easily is with a pigtail kit from MotorMite etc. Make sure the connections are soldered and sealed with weatherproof heat shrink.

Taking the plug off may also have worked a cold/cracked solder joint on a regulator terminal. These can be really annoying to sort out. The fact that messing with the plug had any effect at all hopefully means that the problem is the plug or the regulator.

Also check to make sure both battery cables are clean and have a tight connection. You havent had a real problem yet, but 6 years is pushing it. Id wait for the first time you have a real problem and replace the battery. I generally get 4-5 years on ANY battery. After that 4th year, first problem gets a replacememt. I NEVER buy more that the cheapest Autozone battery for the vehicle. Ive never had an expensive (like $200 mercedes) one last any longer than the cheapest.

I replace the Batterys at 3 years, wheather they are turning bad or not. (like Roger, I use cheapie Autozone batteries)

Is the battery hold down good and tight? The plates are so close if a bump causes the battery to shake and the plates will touch and short causing the light to come on. Happened to me once.

Regardless on the battery holddown, the Silverado has a protective cover over the positive to prevent an accidental short. I understand what you mean about replacing the battery every couple years, but my Silverado is great on that....it's electrical system will automatically kill the entire circuit after a certain amount of time to prevent wearing down a battery. When you have a good quality battery, and never run it down, it will last a LONG time. Mine is 8 years and 160,000 miles old, and I still trust it completely. If only my U-joints were that reliable....do you have to replace yours every 40,000 miles too? Off to do another one tomorrow. At least they are consistent on mileage. For the record, mine hasn't thrown that battery light in over a month now....so I won't worry about it until the problem comes back.

Batteries are really cheap maintanence. A $40 battery that lasts 5 years only costs you $8 @ year. Thats less than a couple of quarts of oil. While it is true some peoples batteries last a lot longer, Ive personally never gotten more than 5 years from one before it started having issues. Batteries dont have any relationship to mileage Ive seen, but they do to time. ie/ If you only do an oil change at 7500 miles by your manual and you only put on 500 miles a year going to shows, does that mean you change it only every 15 years ?

When the battery shakes it's the plates inside the battery that touch and short out not the terminals.

This probably isn't the answer, but....

Make sure its not a slipping / stopping belt due to a problem with another accessory.

This happened recently with my mother's Saturn - An empty power steering reservoir caused the pump to put stress on the serpentine belt. And the same could happen with a bad A/C clutch or a bad waterpump.