Battery not charging
Thread Starter
5th Gear Member
Joined: Jan 2007
Posts: 2,166
From: Oregon
Battery not charging
So over the past couple weeks the 65 has had some problems charging the battery. It has a new battery, I replaced the voltage regulator and I replaced the alternator, which seemed to have fixed the problem until today. I tried starting it up after class and the battery was dead, so I push started it and drove it home, but I noticed it wasn't charging. What do you guys think might be wrong with it? Thanks in advance.
4th Gear Member
Joined: Sep 2006
Posts: 1,188
From: 1984
3rd Gear Member
Joined: Aug 2006
Posts: 886
From: North East Texas on the Red River
Okay guys, let's be more scientific than just "checkiing the alternator."
If you don't have one, you can get a Digital Multimeter for $15 or $20 that is plenty good enough for troubleshooting anything in your car.
Set the DMM on DC volts and start the car even if you have to jump it. With the engine revved up just a little, you should read something like 13.5 to 14 Volts DC with the leads across the battery. If you do have this voltage, the charging system is working. If you don't it's not.
If you had only about 12 Volts when checking the charging system, then having the alternator checked is a legitimate step. If it is good, then do a voltage drop test, by using your meter in DC mode putting the leads across each link of the circuit until you get a Voltage more than about a Volt or a little less. Wherever you have a high voltage drop, that is the weak link in the circuit. The only single component that should give a high voltage drop is across the alternator itself.
If it's charging, then you have a bad battery or a battery drain. Using your DMM as an ammeter in series with one of the battery cables and the battery post AND EVERYTHING TURNED OFF, you should read only a small fraction of an Amp. If you read any more than this you have a drain on the battery. Start removing fuses one at a time while watching the ammeter. When you disconnect the circuit that is draining, the ammeter reading will fall.
Hope this helps.
If you don't have one, you can get a Digital Multimeter for $15 or $20 that is plenty good enough for troubleshooting anything in your car.
Set the DMM on DC volts and start the car even if you have to jump it. With the engine revved up just a little, you should read something like 13.5 to 14 Volts DC with the leads across the battery. If you do have this voltage, the charging system is working. If you don't it's not.
If you had only about 12 Volts when checking the charging system, then having the alternator checked is a legitimate step. If it is good, then do a voltage drop test, by using your meter in DC mode putting the leads across each link of the circuit until you get a Voltage more than about a Volt or a little less. Wherever you have a high voltage drop, that is the weak link in the circuit. The only single component that should give a high voltage drop is across the alternator itself.
If it's charging, then you have a bad battery or a battery drain. Using your DMM as an ammeter in series with one of the battery cables and the battery post AND EVERYTHING TURNED OFF, you should read only a small fraction of an Amp. If you read any more than this you have a drain on the battery. Start removing fuses one at a time while watching the ammeter. When you disconnect the circuit that is draining, the ammeter reading will fall.
Hope this helps.
Thread Starter
5th Gear Member
Joined: Jan 2007
Posts: 2,166
From: Oregon
Okay guys, let's be more scientific than just "checkiing the alternator."
If you don't have one, you can get a Digital Multimeter for $15 or $20 that is plenty good enough for troubleshooting anything in your car.
Set the DMM on DC volts and start the car even if you have to jump it. With the engine revved up just a little, you should read something like 13.5 to 14 Volts DC with the leads across the battery. If you do have this voltage, the charging system is working. If you don't it's not.
If you had only about 12 Volts when checking the charging system, then having the alternator checked is a legitimate step. If it is good, then do a voltage drop test, by using your meter in DC mode putting the leads across each link of the circuit until you get a Voltage more than about a Volt or a little less. Wherever you have a high voltage drop, that is the weak link in the circuit. The only single component that should give a high voltage drop is across the alternator itself.
If it's charging, then you have a bad battery or a battery drain. Using your DMM as an ammeter in series with one of the battery cables and the battery post AND EVERYTHING TURNED OFF, you should read only a small fraction of an Amp. If you read any more than this you have a drain on the battery. Start removing fuses one at a time while watching the ammeter. When you disconnect the circuit that is draining, the ammeter reading will fall.
Hope this helps.
If you don't have one, you can get a Digital Multimeter for $15 or $20 that is plenty good enough for troubleshooting anything in your car.
Set the DMM on DC volts and start the car even if you have to jump it. With the engine revved up just a little, you should read something like 13.5 to 14 Volts DC with the leads across the battery. If you do have this voltage, the charging system is working. If you don't it's not.
If you had only about 12 Volts when checking the charging system, then having the alternator checked is a legitimate step. If it is good, then do a voltage drop test, by using your meter in DC mode putting the leads across each link of the circuit until you get a Voltage more than about a Volt or a little less. Wherever you have a high voltage drop, that is the weak link in the circuit. The only single component that should give a high voltage drop is across the alternator itself.
If it's charging, then you have a bad battery or a battery drain. Using your DMM as an ammeter in series with one of the battery cables and the battery post AND EVERYTHING TURNED OFF, you should read only a small fraction of an Amp. If you read any more than this you have a drain on the battery. Start removing fuses one at a time while watching the ammeter. When you disconnect the circuit that is draining, the ammeter reading will fall.
Hope this helps.
That's what's happening, it's on the left.
3rd Gear Member
Joined: Aug 2006
Posts: 886
From: North East Texas on the Red River
Okay, so it's discharging. That only tells you one thing, that the charging SYSTEM is not charging. It could indeed be and most likely IS the alternator, but it could very easily be a be connection or some other malady. A Voltmeter and a quick Voltage Drop Check can tell you for sure before you waste the time removing the alternator.
1st Gear Member
Joined: Oct 2007
Posts: 106
From: FTW, TX
My old school test: With the car running, disconnect the batt leads. If it quits, its the alternator.
If it keeps running then you have a drain/short, so do as suggested and test one circuit at a time to narrow down where to look for bad wires or bad grounds.
Better yet. Ditch the volt reg and go with a one wire setup with stronger alt. Fixes a lot of problems, especially if you're running extra loads on the system.
If it keeps running then you have a drain/short, so do as suggested and test one circuit at a time to narrow down where to look for bad wires or bad grounds.
Better yet. Ditch the volt reg and go with a one wire setup with stronger alt. Fixes a lot of problems, especially if you're running extra loads on the system.