Voltage drop while driving
Thread Starter
Former Vendor
Joined: Jan 2008
Posts: 16,312
Likes: 0
From: Surprise Arizona
Voltage drop while driving
My car died out on me last night while driving. The car started with 13 plus volts and by the end of the night I noticed it was down to 11.5 and then it keep dropping and dropping till I lost all my accessories and the car died. I jump started the car and it ran for a second then lost voltage and died again.
What's really weird is that I noticed at one moment the volts were at 12 then a second later it went up to 13.5? If the alternator was dead wouldn't it just drop volts and not go up?
The car currently won't start due to the battery being drained. Do you guys think my alternator is dead or maybe even the battery. What's funny is that both the battery (Optima red top) and alternator (custom alternator from Race Proven) are only 2 months old.
My alternator is right next to my turbo manifolds (PTK turbo kit) so I'm wondering if the heat might of burnt it out.
What's really weird is that I noticed at one moment the volts were at 12 then a second later it went up to 13.5? If the alternator was dead wouldn't it just drop volts and not go up?
The car currently won't start due to the battery being drained. Do you guys think my alternator is dead or maybe even the battery. What's funny is that both the battery (Optima red top) and alternator (custom alternator from Race Proven) are only 2 months old.
My alternator is right next to my turbo manifolds (PTK turbo kit) so I'm wondering if the heat might of burnt it out.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Sounds more like a loose (intermittent open circuit) connection. Check them all, especially the one at the starter solenoid. Grounds too, but especially the "hot" (B+) connections.
If all is well there, then start looking elsewhere.
If all is well there, then start looking elsewhere.
Advanced
Joined: May 2007
Posts: 97
Likes: 0
From: Sterling VA
Some things to check
Check the battery terminals first. Remove them and inspect for signs of corrosion.
Recharge the battery to full capacity. Let it sit for about two hours. It should measure about 12.6 volts after charging with no connections, maybe a tad higher. Anything lower indicates you have a cell in the battery that is soft.
My own personal experience in the past with voltage going up and down tracked back to corroded battery terminals on one vehicle. It was so bad that the car would suddenly shut down and lights go off in the middle of the night. Very disconcerting on I-95 during rush hour in the winter.
The other reason for the voltage fluctuating on a second vehicle was a bad set of diodes in the alternator. Two of the six diodes had overheated at some point and mechanically separated. Under varying temperature conditions the diodes would make and then break. The alternator could not keep the battery properly charged and eventually the battery gave up.
Wish I could be more help.
Recharge the battery to full capacity. Let it sit for about two hours. It should measure about 12.6 volts after charging with no connections, maybe a tad higher. Anything lower indicates you have a cell in the battery that is soft.
My own personal experience in the past with voltage going up and down tracked back to corroded battery terminals on one vehicle. It was so bad that the car would suddenly shut down and lights go off in the middle of the night. Very disconcerting on I-95 during rush hour in the winter.
The other reason for the voltage fluctuating on a second vehicle was a bad set of diodes in the alternator. Two of the six diodes had overheated at some point and mechanically separated. Under varying temperature conditions the diodes would make and then break. The alternator could not keep the battery properly charged and eventually the battery gave up.
Wish I could be more help.
Thread Starter
Former Vendor
Joined: Jan 2008
Posts: 16,312
Likes: 0
From: Surprise Arizona
It looks like the problem is the alternator. I have a warranty on it so I will be sending it back to get repaired. Thanks for the help. 
Check the battery terminals first. Remove them and inspect for signs of corrosion.
Recharge the battery to full capacity. Let it sit for about two hours. It should measure about 12.6 volts after charging with no connections, maybe a tad higher. Anything lower indicates you have a cell in the battery that is soft.
My own personal experience in the past with voltage going up and down tracked back to corroded battery terminals on one vehicle. It was so bad that the car would suddenly shut down and lights go off in the middle of the night. Very disconcerting on I-95 during rush hour in the winter.
The other reason for the voltage fluctuating on a second vehicle was a bad set of diodes in the alternator. Two of the six diodes had overheated at some point and mechanically separated. Under varying temperature conditions the diodes would make and then break. The alternator could not keep the battery properly charged and eventually the battery gave up.
Wish I could be more help.
Recharge the battery to full capacity. Let it sit for about two hours. It should measure about 12.6 volts after charging with no connections, maybe a tad higher. Anything lower indicates you have a cell in the battery that is soft.
My own personal experience in the past with voltage going up and down tracked back to corroded battery terminals on one vehicle. It was so bad that the car would suddenly shut down and lights go off in the middle of the night. Very disconcerting on I-95 during rush hour in the winter.
The other reason for the voltage fluctuating on a second vehicle was a bad set of diodes in the alternator. Two of the six diodes had overheated at some point and mechanically separated. Under varying temperature conditions the diodes would make and then break. The alternator could not keep the battery properly charged and eventually the battery gave up.
Wish I could be more help.
Burning Brakes
Joined: Oct 2004
Posts: 925
Likes: 4
From: EXTON PA
My car died out on me last night while driving. The car started with 13 plus volts and by the end of the night I noticed it was down to 11.5 and then it keep dropping and dropping till I lost all my accessories and the car died. I jump started the car and it ran for a second then lost voltage and died again.
What's really weird is that I noticed at one moment the volts were at 12 then a second later it went up to 13.5? If the alternator was dead wouldn't it just drop volts and not go up?
The car currently won't start due to the battery being drained. Do you guys think my alternator is dead or maybe even the battery. What's funny is that both the battery (Optima red top) and alternator (custom alternator from Race Proven) are only 2 months old.
My alternator is right next to my turbo manifolds (PTK turbo kit) so I'm wondering if the heat might of burnt it out.
What's really weird is that I noticed at one moment the volts were at 12 then a second later it went up to 13.5? If the alternator was dead wouldn't it just drop volts and not go up?
The car currently won't start due to the battery being drained. Do you guys think my alternator is dead or maybe even the battery. What's funny is that both the battery (Optima red top) and alternator (custom alternator from Race Proven) are only 2 months old.
My alternator is right next to my turbo manifolds (PTK turbo kit) so I'm wondering if the heat might of burnt it out.
Thread Starter
Former Vendor
Joined: Jan 2008
Posts: 16,312
Likes: 0
From: Surprise Arizona
Your Red Top Battery does not like to be drained but a total drain to a dead battery does harm the battery and its recovery. Once you get the problem tracked down be sure that your battery is not damaged. Your custom alternator is designed to produce what output. The OEM output is Plus 105-110. Any thing less is not a match to the car's need
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Btw, an alternator will not put out more amps than what is demanded of it. It does not "hurt" a thing to have a high amp output alternator (other than maybe your wallet) and what it DOES do for you (mainly) is that it puts out more current AT IDLE than a low(er) amp output alternator and it of course provides the additional amperage for any add-on equipment; typically high powered stereos, etc.
Thread Starter
Former Vendor
Joined: Jan 2008
Posts: 16,312
Likes: 0
From: Surprise Arizona
Just get it load tested if you are uncertain about it.
Btw, an alternator will not put out more amps than what is demanded of it. It does not "hurt" a thing to have a high amp output alternator (other than maybe your wallet) and what it DOES do for you (mainly) is that it puts out more current AT IDLE than a low(er) amp output alternator and it of course provides the additional amperage for any add-on equipment; typically high powered stereos, etc.
Btw, an alternator will not put out more amps than what is demanded of it. It does not "hurt" a thing to have a high amp output alternator (other than maybe your wallet) and what it DOES do for you (mainly) is that it puts out more current AT IDLE than a low(er) amp output alternator and it of course provides the additional amperage for any add-on equipment; typically high powered stereos, etc.
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