Alternator or battery problem?
Question:
I went to start my 90 gmc up and the battery was dead.There was not anything left on and it has never happened before.I jump started it and drove it around and while it was running the guage said 12-14 volts.I turned off the truck and tried to restart it and nothing.I did that twice.Is my battery just dead and won’t live again or is it the alternator not charging?Any tips on how to check this stuff?Thanks
Response:
You could test further before making the decision, but the battery is most likely dead.
I went to start my 90 gmc up and the battery was dead.There was not anything left on and it has never happened before.I jump started it and drove it around and while it was running the guage said 12-14 volts.I turned off the truck and tried to restart it and nothing.I did that twice.Is my battery just dead and won’t live again or is it the alternator not charging?Any tips on how to check this stuff?Thanks
Response:
How old is the battery? If it is older than 36 months, I would kind of blame it. BUT, you need to have the alternator checked first! An alternator shop will be willing to check it for you. I have always found that many problems with sudden battery failure stem from improper charging. – Hide quoted text — Show quoted text – > I went to start my 90 gmc up and the battery was dead.There was not > anything left on and it has never happened before.I jump started it and > drove it around and while it was running the guage said 12-14 volts.I > turned off the truck and tried to restart it and nothing.I did that > twice.Is my battery just dead and won’t live again or is it the > alternator not charging?Any tips on how to check this stuff?Thanks
Response:
If the battery is low the alternator can put up to 18 volts while charging. A good battery will tend to read close to 13 volts if charged 12 volts and below and it likely suspect. I would guess from the behavior that this is a Delco "no freedom" battery. The tend to go like this. Is it possible the battery might have been subject to really cold weather in its lifetime. This can drastically shorten the life of some of the no maintenance batteries. – Hide quoted text — Show quoted text – >Your dash voltmeter will give you some idea of what is wrong. Not the most >accurate diagnostic tool but will do in a pinch. 12 – 14 while running >should be indicating the alt is basically ok. The next thing would be to >see what the voltmeter reads after running the engine for a while , >shutting the engine off , and then turning the key back to "on" without >starting the engine. If it reads 12 then the battery may be ok. Less >could indicate the battery won’t take a charge. Is this the original 1990 >battery? If it is then the age plus the info you provided would make me >think the battery has seen it’s last good day. While you are at it check >to be sure the cable connections are bright and shiney and tight. The side >post batteries can be pretty crappy and still look ok from the outside. >or so rpm with no load on it. A good vehicle repair manual should have the >exact numbers for your alternator. >– >Mike ( Anti Spam Address ) >"Opportunites are spawned from crisis" >I went to start my 90 gmc up and the battery was dead.There was not >anything left on and it has never happened before.I jump started it and >drove it around and while it was running the guage said 12-14 volts.I >turned off the truck and tried to restart it and nothing.I did that >twice.Is my battery just dead and won’t live again or is it the >alternator not charging?Any tips on how to check this stuff?Thanks
Response:
Your dash voltmeter will give you some idea of what is wrong. Not the most accurate diagnostic tool but will do in a pinch. 12 – 14 while running should be indicating the alt is basically ok. The next thing would be to see what the voltmeter reads after running the engine for a while , shutting the engine off , and then turning the key back to "on" without starting the engine. If it reads 12 then the battery may be ok. Less could indicate the battery won’t take a charge. Is this the original 1990 battery? If it is then the age plus the info you provided would make me think the battery has seen it’s last good day. While you are at it check to be sure the cable connections are bright and shiney and tight. The side post batteries can be pretty crappy and still look ok from the outside. or so rpm with no load on it. A good vehicle repair manual should have the exact numbers for your alternator. — Mike ( Anti Spam Address ) "Opportunites are spawned from crisis" I went to start my 90 gmc up and the battery was dead.There was not anything left on and it has never happened before.I jump started it and drove it around and while it was running the guage said 12-14 volts.I turned off the truck and tried to restart it and nothing.I did that twice.Is my battery just dead and won’t live again or is it the alternator not charging?Any tips on how to check this stuff?Thanks
Response:
Thanks guys for all the responces.I am going this evening to check the alt.Last night I jumped it off again and while running unhooked the battery.I have always heard that if you do this and it dies the alt i bad.If it runs it’s the battery.Is that true?It did keep running BTW.
Response:
That’s the sure way to kill off the electronics in a newer car+ACE- The Alternator puts out power, not volts or amps and when you released it’s big load handler (the battery) it jumped the voltage up until the power came back to equilibrium and then the regulator came into effect and dropped the voltage back down. That all happens in milliseconds but that’s all that’s needed for electronics. I worked for a company that deals in commercial vehicle applications of electonics and the spec we had to meet for our electronics was 144V for 150ms.+ACE- That’s not chickenfeed folks. That’s about a cubic foot of capicator bank and a good size power supply to charge it and a bunch of very low resistance wire to insure that everything is correct. Bob May
Response:
Sounds like the battery to me. A common problem is that the battery will not take a charge. It has just a bit of capacity. Do your headlights work? Do you have a small (5 to 10 amp) charger? When running the voltage regulator in the vehicle keeps the charge voltage below about 14.5 volts. If the headlights dim rapidly after turning the engine off it is the battery or a very poor connection. Put a charger on the battery and see if it pulls any current. A bad battery will read 14 to 15 volts with no charge current. Dick – Hide quoted text — Show quoted text – > Your dash voltmeter will give you some idea of what is wrong. Not the most > accurate diagnostic tool but will do in a pinch. 12 – 14 while running > should be indicating the alt is basically ok. The next thing would be to > see what the voltmeter reads after running the engine for a while , > shutting the engine off , and then turning the key back to "on" without > starting the engine. If it reads 12 then the battery may be ok. Less > could indicate the battery won’t take a charge. Is this the original 1990 > battery? If it is then the age plus the info you provided would make me > think the battery has seen it’s last good day. While you are at it check > to be sure the cable connections are bright and shiney and tight. The side > post batteries can be pretty crappy and still look ok from the outside. > or so rpm with no load on it. A good vehicle repair manual should have the > exact numbers for your alternator. > — > Mike ( Anti Spam Address ) > "Opportunites are spawned from crisis" > I went to start my 90 gmc up and the battery was dead.There was not > anything left on and it has never happened before.I jump started it and > drove it around and while it was running the guage said 12-14 volts.I > turned off the truck and tried to restart it and nothing.I did that > twice.Is my battery just dead and won’t live again or is it the > alternator not charging?Any tips on how to check this stuff?Thanks
Response:
I am reminded of another method of checking batteries. First you press the horn button. If instead of blowing it makes kind of a sucking sound, the battery is most likely bad. If you still are not convinced you turn on the headlights in bright sunlight. If they cast a shadow on the ground it must be the battery. Dick N0CK
Response:
> I am reminded of another method of checking batteries. > First you press the horn button. If instead of blowing it makes kind of > a sucking sound, the battery is most likely bad. > If you still are not convinced you turn on the headlights in bright > sunlight. If they cast a shadow on the ground it must be the battery. > Dick > N0CK
Or you can buy a cheap VOM for about $5 and end all this horn-sucking foolishness. — Joe
Response:
You did not take me seriously did you? Being a retired EE and a HAM, I have a half dozen meters. Digital and analog. Dick N0CK – Hide quoted text — Show quoted text -> I am reminded of another method of checking batteries. > First you press the horn button. If instead of blowing it makes kind of > a sucking sound, the battery is most likely bad. > If you still are not convinced you turn on the headlights in bright > sunlight. If they cast a shadow on the ground it must be the battery. > Dick > N0CK > Or you can buy a cheap VOM for about $5 and end all this horn-sucking > foolishness. > — > Joe
Response:
I thought the shadow part was pretty good<g>. – Hide quoted text — Show quoted text – >You did not take me seriously did you? Being a retired EE and a HAM, I >have a half dozen meters. Digital and analog. >Dick >N0CK > > I am reminded of another method of checking batteries. > > First you press the horn button. If instead of blowing it makes kind of > > a sucking sound, the battery is most likely bad. > > If you still are not convinced you turn on the headlights in bright > > sunlight. If they cast a shadow on the ground it must be the battery. > > Dick > > N0CK > Or you can buy a cheap VOM for about $5 and end all this horn-sucking > foolishness. > — > Joe
Response:
Thanks Bob but it has no electronics other than the guages.I got rid of it for a carb.
Response:
> I went to start my 90 gmc up and the battery was dead.There was not > anything left on and it has never happened before.I jump started it and > drove it around and while it was running the guage said 12-14 volts.I > turned off the truck and tried to restart it and nothing.I did that > twice.Is my battery just dead and won’t live again or is it the > alternator not charging?Any tips on how to check this stuff?Thanks
Clean the battery terminals and check belt tension. — Tekkie
Response:
– Hide quoted text — Show quoted text -> I went to start my 90 gmc up and the battery was dead.There was not > anything left on and it has never happened before.I jump started it and > drove it around and while it was running the guage said 12-14 volts.I > turned off the truck and tried to restart it and nothing.I did that > twice.Is my battery just dead and won’t live again or is it the > alternator not charging?Any tips on how to check this stuff?Thanks > Clean the battery terminals and check belt tension. > — > Tekkie > Begin by getting your battery charged up by using a battery charger.
If it won’t charge it is a dead give away the battery is shot. After getting the battery charged practically any place that sells batteries should be able to perform a load test on it, just take the battery to them they should be able to check it out probably won’t cost you anything to have load test ran on it it just takes about 15 seconds. If it tests Ok,you have a problem else where, make sure you have a dependable volt meter and hook it up to the battery terminals correctly check voltage then start engine check voltage again. Fully charged battery should read around 12 .5 volts with no load on it. With the engine running turn on all assesories check voltage with engine slightly speeded up it should read aprox. 13 – 14 .5 volts if it doesn’t improve when engine is running or if it shows less then 12 .5 volts you have a problem with your charging system. Shut off engine check connections from battery to alt. look over the belt make sure its Okay. If all looks Okay you should be able to take alt. in to most auto parts stores have them check it out.Shouldn’t cost anything to have it tested call ahead make sure they can test it. Share what you know. Learn what you don’t.
Response:
Actually the reverse is true. Hot weather causes more premature sealed batter failures than cold weather. If the charging system is putting out more than 15 VDC measure with an accurate digital voltmeter, then you should have it checked. The normal output at higher RPMs while the battery is charging is between 14.4 and 14.6 VDC depending on the temperature. It will tamper off to approximately 13.8 VDC when the battery is fully charged again at high RPM. Here are the major questions that are covered in my latest copy of the Car Battery FAQ: 1. WHAT IS THE BOTTOM LINE? 2. WHY BOTHER? 3. HOW DO I PERFORM PREVENTATIVE MAINTENANCE? 4. HOW DO I TEST A BATTERY? 5. HOW DO I KNOW IF THE CHARGING SYSTEM IS OK? 6. HOW DO I JUMP START MY CAR? 7. WHAT DO I LOOK FOR IN BUYING A NEW BATTERY? 8. HOW DO I INSTALL A NEW BATTERY? 9. HOW DO I RECHARGE MY BATTERY? 10. WHAT IS PARASITIC LOAD? 11. HOW CAN I INCREASE THE LIFE OF MY BATTERY? 12. WHAT ARE THE MOST COMMON CAUSES OF PREMATURE BATTERY FAILURES? 13. WHAT ARE THE MYTHS ABOUT BATTERIES? 14. WHERE CAN I FIND MORE INFO ON BATTERIES? If you (or anyone else) would like a copy of the latest version, Deep Cycle Battery FAQ 2.2 or Car Battery FAQ 2.2, they are on the nyquist.ee.ualberta.ca/~schmaus Web server or email me at Regards, BiLL……. – Hide quoted text — Show quoted text – >If the battery is low the alternator can put up to 18 volts while charging. >A good battery will tend to read close to 13 volts if charged 12 volts and >below and it likely suspect. I would guess from the behavior that this is a >Delco "no freedom" battery. The tend to go like this. Is it possible the >battery might have been subject to really cold weather in its lifetime. >This can drastically shorten the life of some of the no maintenance >batteries. >Your dash voltmeter will give you some idea of what is wrong. Not the most >accurate diagnostic tool but will do in a pinch. 12 – 14 while running >should be indicating the alt is basically ok. The next thing would be to >see what the voltmeter reads after running the engine for a while , >shutting the engine off , and then turning the key back to "on" without >starting the engine. If it reads 12 then the battery may be ok. Less >could indicate the battery won’t take a charge. Is this the original 1990 >battery? If it is then the age plus the info you provided would make me >think the battery has seen it’s last good day. While you are at it check >to be sure the cable connections are bright and shiney and tight. The side >post batteries can be pretty crappy and still look ok from the outside. >or so rpm with no load on it. A good vehicle repair manual should have the >exact numbers for your alternator. >– >Mike ( Anti Spam Address ) >"Opportunites are spawned from crisis" >I went to start my 90 gmc up and the battery was dead.There was not >anything left on and it has never happened before.I jump started it and >drove it around and while it was running the guage said 12-14 volts.I >turned off the truck and tried to restart it and nothing.I did that >twice.Is my battery just dead and won’t live again or is it the >alternator not charging?Any tips on how to check this stuff?Thanks
Response:
Dick, You are correct in that you need a digital voltmeter with .5% or better accuracy to measure the state-of-charge of a battery and the output of a charging system. Regards, BiLL….. – Hide quoted text — Show quoted text – >You did not take me seriously did you? Being a retired EE and a HAM, I >have a half dozen meters. Digital and analog. >Dick >N0CK > > I am reminded of another method of checking batteries. > > First you press the horn button. If instead of blowing it makes kind of > > a sucking sound, the battery is most likely bad. > > If you still are not convinced you turn on the headlights in bright > > sunlight. If they cast a shadow on the ground it must be the battery. > > Dick > > N0CK > Or you can buy a cheap VOM for about $5 and end all this horn-sucking > foolishness. > — > Joe
Response:
Great suggestion! Regards, BiLL….. – Hide quoted text — Show quoted text -> I went to start my 90 gmc up and the battery was dead.There was not > anything left on and it has never happened before.I jump started it and > drove it around and while it was running the guage said 12-14 volts.I > turned off the truck and tried to restart it and nothing.I did that > twice.Is my battery just dead and won’t live again or is it the > alternator not charging?Any tips on how to check this stuff?Thanks >Clean the battery terminals and check belt tension. >– >Tekkie
Response:
> I am reminded of another method of checking batteries. > First you press the horn button. If instead of blowing it makes kind of > a sucking sound, the battery is most likely bad. > If you still are not convinced you turn on the headlights in bright > sunlight. If they cast a shadow on the ground it must be the battery.
This phenomena was covered in detail by _POPULAR_ELECTRONICS_ magazine back in the late 50’s and was called CONTRAPOLAR ENERGY. Turn on the light and the room would get dark in addition to your electric oven get- ting cold and refrigerator getting hot. I wish auto makers would include both voltmeter AND ammeter – they’d tell more about battery/charging condition than a voltmeter alone or idiot light. Don Montgomery Poor auto mechanic, better EE.
Response:
– Hide quoted text — Show quoted text -> > I went to start my 90 gmc up and the battery was dead.There was not > > anything left on and it has never happened before.I jump started it > and > > drove it around and while it was running the guage said 12-14 > volts.I > > turned off the truck and tried to restart it and nothing.I did that > > twice.Is my battery just dead and won’t live again or is it the > > alternator not charging?Any tips on how to check this stuff?Thanks > Clean the battery terminals and check belt tension. > — > Tekkie > Begin by getting your battery charged up by using a battery charger. > If it won’t charge it is a dead give away the battery is shot. After > getting the battery charged practically any place that sells batteries > should be able to perform a load test on it, just take the battery to > them they should be able to check it out probably won’t cost you
I wouldn’t even trust the load tests as they, too, can sometimes lie. I had this problem with my vehicle. I used a load tester on it and it did show up ok. But it was clear to see that the battery was getting its power from the alternator, just that the battery didn’t seem to be taking it in. By using an ammeter, I checked for any current flow into the battery, and lo-and-behold, nothing. So IMHO, I strongly recommend using an voltmeter (and some mathematics) to check to see if the battery is accepting a charge at all. This doesn’t mean placing an ammeter in series with the positive line of the battery (only a true industrial meter could handle so much current in it), but actually checking for current flow between the battery’s negative terminal and chassis over a little piece of wire of known resistance (shunt). — Adios, LarZ Replace "nospam" with "larz" for email replies
Response:
IMHO, also check that the wire between the battery and car are still good. I had that problem. Poor grounding made me think the battery was down. You can jump start it, the alternator kept it going, but when trying to start on its own, the poor contact cause too much resistance. Hope it helps.
Response:
I’d charge the battery and then get the battery load tested. Gregg
