I am having trouble with my batteries not charging. The car is great when it's running. But when I cut it off and try to start it the battery is dead. I jump it off and it goes again. Same thing when I cut it off. The alternator has to be charging enough to run the car but the battery is not charged. I have tried different batteries so that is not the problem. Any suggestions, idea's, are welcome.
1969 road runner 440
- Thread starter barf75
- Start date
Mike67
Well-Known Member
So with the car off, have you tried lifting the terminal off of the post to see if it has current on it? You would see an arc, or here it arcing...
Take the alt to a parts house that can test it...
Take the alt to a parts house that can test it...
PurpleBeeper
Well-Known Member
Mike is right. It's probably a bad alternator.
Your choices are:
a. battery
b. alternator
c. voltage regulator
d. under-hood wiring (e.g. the main power wire from alternator to battery or one of the field wires)
e. corroded battery terminals
f. poor ground to the block/chassis at the negative battery terminal
Your choices are:
a. battery
b. alternator
c. voltage regulator
d. under-hood wiring (e.g. the main power wire from alternator to battery or one of the field wires)
e. corroded battery terminals
f. poor ground to the block/chassis at the negative battery terminal
Mike67
Well-Known Member
It depends, if there is enough of a charge in the battery to supply the minimal voltage it needs it would run for a little while...before stalling....You never said how long it ran before you shut it off and tried to restart.
Personally I think you have a parasitic draw on your battery thats keeping it low enough to not start. But it could be a combination as well.
The arc test is the easiest thing to do...If it does show a draw pull the fuses one at a time until there is no draw, whatever that circuit feeds is where the problem likely is.
Personally I think you have a parasitic draw on your battery thats keeping it low enough to not start. But it could be a combination as well.
The arc test is the easiest thing to do...If it does show a draw pull the fuses one at a time until there is no draw, whatever that circuit feeds is where the problem likely is.
Let's do a simple check of the Electromotive Force that is very easy. Grab a DMM, or voltmeter. Jump the car and start it. Remove jumper cables.
Measure the battery voltage. At idle, optimum should read 13.8V, and can be as high as 15, or so. Let idle a few minutes. Turn on high beams, blower motor, hazard flashers and measure voltage. Still should be in the range of 13.8, or so.
Shut off car, and measure battery voltage. MUST be greater than 12V. If not, it could be the battery, or any of the other items mentioned above.
Measure the battery voltage. At idle, optimum should read 13.8V, and can be as high as 15, or so. Let idle a few minutes. Turn on high beams, blower motor, hazard flashers and measure voltage. Still should be in the range of 13.8, or so.
Shut off car, and measure battery voltage. MUST be greater than 12V. If not, it could be the battery, or any of the other items mentioned above.
Ranger16
Well-Known Member
Static battery voltage readings
I should also caution against the battery arc test in that a gassy battery could explode. I do not recommend this test. There is also the effect of 'load dump' (SAE term) when the battery disconnect test is performed on a running vehicle. In a nutshell, the feedback loop of the old style regulators could cause a 70V spike in the power rail with the battery disconnected during alternator charging operation. It is a 250 millisecond pulse that probably won't hurt older car systems, but the electronic ignition upgrades and the newer low cost stereos will surely be damaged.
Mike67
Well-Known Member
How many exploded batteries have you seen??? Anytime you disconnect a battery you could have an arc. I guess if you were to let it sit in an airtight box for a month the off gas could explode with an arc...but not likely.
I worked on UPS/ SEPPS at the plants that were all lead acid batteries in a 30x70 room filled with close to 500 batteries. We checked specific gravity and changed them all the time and never blew up. That was a caustic room! You would smell sulfur for 3 days after....
I worked on UPS/ SEPPS at the plants that were all lead acid batteries in a 30x70 room filled with close to 500 batteries. We checked specific gravity and changed them all the time and never blew up. That was a caustic room! You would smell sulfur for 3 days after....
Only one, and that was with a lit cigarette in my friends hand. I still think it's playing with fire, but to each his own.
PurpleBeeper
Well-Known Member
Yeah, but I've had it happen to me with ONE of TWO field wires being bad. It takes virtually no electricity to run your engine.....like you could run it off a flashlight battery almost.... but it DOES take a lot of electricity to turn the starter. I'd still check the alternator. I've also had one diode (of 3?) go bad in a Mustang alternator & the car all tested "good", but the battery would drain down when I drove it in the rain (headlights + defrost + wipers + cooling fans + brake lights in traffic) and not start the next day.
OK charger
Well-Known Member
PB is right. Mopar alternators from that year have the two fields. When you go to have your alternator tested make sure they test BOTH fields. Just simply reverse the wires being tested.
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Gee,
Just place a multi-meter on the battery terminals as car is running
Check for 13+ to 14.2 volts on the battery
This tells you if alternator is charging
Also: Is your battery "Holding" a Charge?
Just place a multi-meter on the battery terminals as car is running
Check for 13+ to 14.2 volts on the battery
This tells you if alternator is charging
Also: Is your battery "Holding" a Charge?
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