What does battery light indicate?
Question:
Steve, that may be true in some areas. Where I live, there are big signs in the parking lots of the auto parts stores that forbid doing repair work in the lots. It is a zoning thing. I’ve always found it better to do the repair back home in my garage, where I have everything that I need. Then, once it is repaired, I can drive back to the auto parts store as a test-drive of the repair. —Bob Gross—
– Hide quoted text — Show quoted text -> True statement, I myself have done the diagnosis before the rushing out an > buying an alternator, but after 2 or three times it’s just easier to drive > right to the parts store when you see the battery light come on. There were > a few times I just saw the light, drove to the local auto parts store, > walked in, bought an alternator walked out to the car, grabbed my 19MM, 13MM > and 10MM wrenches out of the trunk, and changed the alternator in the > parking lot in about 5 minutes. The good thing is: you can get your core > credit right away. > Steve
Response:
They have those signs at the parts stores in my area too. We also have highway signs that say "Speed Limit 65", "No Travelling in Breakdown Lane", "No Turn on Red" etc. Apparently all these signs are installed just to keep sign makers busy as most if not all go unheeded and violaters go unpunished. — "Opportunities are spawned from crisis"
Steve, that may be true in some areas. Where I live, there are big signs in the parking lots of the auto parts stores that forbid doing repair work in the lots. It is a zoning thing.
Response:
The charge indicator light will come on any time the alternators output voltage is less than the battery voltage. Sounds like it is working correctly in both instances. Connect a simple volt meter to the battery terminals and run the engine up past a fast idle – the volt meter should read 13.6 to 14.3 volts or so if the alternator is charging properly. — "Opportunities are spawned from crisis"
1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and runs. I have a voltage indicator on the instrument panel. It was indicating in the yellow and the battery dummy light was illuminated. I replaced the battery. Now the voltage when running is just out of the yellow range but the battery light is still on. What is the battery light indicating? Barry
Response:
On some GM vehicles of that era, you can "blow out" some of the sections of the alternator (actually the rectifiers) and the alternator will then have reduced output. It still works, but not fully. With a good test system, you can spot that in voltage and current. —Bob Gross— – Hide quoted text — Show quoted text -> The charge indicator light will come on any time the alternators output > voltage is less than the battery voltage. > Sounds like it is working correctly in both instances. > Connect a simple volt meter to the battery terminals and run the engine up > past a fast idle – the volt meter should read 13.6 to 14.3 volts or so if > the alternator is charging properly. > — > "Opportunities are spawned from crisis" > 1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and > runs. I have a voltage indicator on the instrument panel. It was > indicating in the yellow and the battery dummy light was illuminated. > I replaced the battery. Now the voltage when running is just out of > the yellow range but the battery light is still on. What is the > battery light indicating? > Barry
Response:
On mid-late 80’s vehicles a GM (Delco) Alternator, the internal voltage regulator is controlled by three diodes. Diode faults are generally the cause of alternator failure. Only ONE of the diodes controls the battery light. If that is not the one that faults, then you will have reduced output until your battery goes dead. The only way to find it is an charging system checkout. – Hide quoted text — Show quoted text – > On some GM vehicles of that era, you can "blow out" some of the sections of > the alternator (actually the rectifiers) and the alternator will then have > reduced output. It still works, but not fully. With a good test system, you > can spot that in voltage and current. > —Bob Gross— > The charge indicator light will come on any time the alternators output > voltage is less than the battery voltage. > Sounds like it is working correctly in both instances. > Connect a simple volt meter to the battery terminals and run the engine up > past a fast idle – the volt meter should read 13.6 to 14.3 volts or so if > the alternator is charging properly. > — > "Opportunities are spawned from crisis" > 1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and > runs. I have a voltage indicator on the instrument panel. It was > indicating in the yellow and the battery dummy light was illuminated. > I replaced the battery. Now the voltage when running is just out of > the yellow range but the battery light is still on. What is the > battery light indicating? > Barry
Response:
Yes, I had one rectifer section fail (with a "snap" sound) and the alternator still worked so-so. Then I had a second section fail, and it still worked just a little. It could not power up headlights and run the car, but the car would run if I used no lights or accessories at all. Obviously, that alternator got replaced a day later. I did not need any charging system check to see what was going on. —Bob Gross— – Hide quoted text — Show quoted text -> On mid-late 80’s vehicles a GM (Delco) Alternator, the internal voltage > regulator is controlled by three diodes. Diode faults are generally the cause > of alternator failure. Only ONE of the diodes controls the battery light. If > that is not the one that faults, then you will have reduced output until your > battery goes dead. The only way to find it is an charging system checkout. > On some GM vehicles of that era, you can "blow out" some of the sections of > the alternator (actually the rectifiers) and the alternator will then have > reduced output. It still works, but not fully. With a good test system, you > can spot that in voltage and current.
Response:
True statement, I myself have done the diagnosis before the rushing out an buying an alternator, but after 2 or three times it’s just easier to drive right to the parts store when you see the battery light come on. There were a few times I just saw the light, drove to the local auto parts store, walked in, bought an alternator walked out to the car, grabbed my 19MM, 13MM and 10MM wrenches out of the trunk, and changed the alternator in the parking lot in about 5 minutes. The good thing is: you can get your core credit right away. Steve
– Hide quoted text — Show quoted text -> SM, > I just wanted to make sure he didn’t rush out and spend the money without > thorough diagnosis. > I could have written that better. > GW > I have to disagree with Geoff’s statistic, "9 out of ten times that means > the alternator is bad." When it comes to GM products, when the battery light > comes on, you can be 99.99% sure it’s the alternator. > 
Steve > 3 cars, 1992 Lumina 3.1 (5 alternators in 8 years), 1995 Z34 3.4 (2 > alternators in 3 weeks), 1988 Z24 2.8 (4 alternators in 4 years)……. > > >1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and > > >runs. I have a voltage indicator on the instrument panel. It was > > >indicating in the yellow and the battery dummy light was illuminated. > > >I replaced the battery. Now the voltage when running is just out of > > >the yellow range but the battery light is still on. What is the > > >battery light indicating? > > >Barry > — > or click on
Response:
It indicates low voltage in the charging system. 9 out of 10 times that means the alternator is bad. The rest of the time it’s a wiring problem. (loose, dirty, chafed….) GW – Hide quoted text — Show quoted text – > 1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and > runs. I have a voltage indicator on the instrument panel. It was > indicating in the yellow and the battery dummy light was illuminated. > I replaced the battery. Now the voltage when running is just out of > the yellow range but the battery light is still on. What is the > battery light indicating? > Barry
Response:
1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and runs. I have a voltage indicator on the instrument panel. It was indicating in the yellow and the battery dummy light was illuminated. I replaced the battery. Now the voltage when running is just out of the yellow range but the battery light is still on. What is the battery light indicating? Barry
Response:
SM, I just wanted to make sure he didn’t rush out and spend the money without thorough diagnosis. I could have written that better. GW – Hide quoted text — Show quoted text – > I have to disagree with Geoff’s statistic, "9 out of ten times that means > the alternator is bad." When it comes to GM products, when the battery light > comes on, you can be 99.99% sure it’s the alternator. > Steve > 3 cars, 1992 Lumina 3.1 (5 alternators in 8 years), 1995 Z34 3.4 (2 > alternators in 3 weeks), 1988 Z24 2.8 (4 alternators in 4 years)……. > >1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and > >runs. I have a voltage indicator on the instrument panel. It was > >indicating in the yellow and the battery dummy light was illuminated. > >I replaced the battery. Now the voltage when running is just out of > >the yellow range but the battery light is still on. What is the > >battery light indicating? > >Barry
– or click on
Response:
– Hide quoted text — Show quoted text – >1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and >runs. I have a voltage indicator on the instrument panel. It was >indicating in the yellow and the battery dummy light was illuminated. >I replaced the battery. Now the voltage when running is just out of >the yellow range but the battery light is still on. What is the >battery light indicating? >Barry
Response:
I have to disagree with Geoff’s statistic, "9 out of ten times that means the alternator is bad." When it comes to GM products, when the battery light comes on, you can be 99.99% sure it’s the alternator. Steve 3 cars, 1992 Lumina 3.1 (5 alternators in 8 years), 1995 Z34 3.4 (2 alternators in 3 weeks), 1988 Z24 2.8 (4 alternators in 4 years)……. – Hide quoted text — Show quoted text ->1989 GMC Safari. Would not start. Replaced starter. Vehicle starts and >runs. I have a voltage indicator on the instrument panel. It was >indicating in the yellow and the battery dummy light was illuminated. >I replaced the battery. Now the voltage when running is just out of >the yellow range but the battery light is still on. What is the >battery light indicating? >Barry
