Battery Voltage Problem
Thread Starter
Instructor
Joined: Jan 2009
Posts: 106
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From: Marietta GA
Battery Voltage Problem
Car got all new wiring harness (engine & cabin) along with new battery cables and battery around 5 months ago.
Well...went to go for a ride on Saturday and car did not turn over at all. Car was cranking right up and no problems for the last 5 months. It had been one week since I had driven her.
So I did some testing today and when trying to jump the car the starter would not engage strong enough. (both with key and trigger starter direct to the starter) I then decided to do some voltage tests on the battery.
Battery is registering 14 volts at the battery, horn relay & alternator. When I push the horn button....the voltage drops to around 8 volts and slowly works it way up to 14 again.
Is this a sign of a bad battery not being able to handle load? Or do I possibly have other electric gremlins?
Well...went to go for a ride on Saturday and car did not turn over at all. Car was cranking right up and no problems for the last 5 months. It had been one week since I had driven her.
So I did some testing today and when trying to jump the car the starter would not engage strong enough. (both with key and trigger starter direct to the starter) I then decided to do some voltage tests on the battery.
Battery is registering 14 volts at the battery, horn relay & alternator. When I push the horn button....the voltage drops to around 8 volts and slowly works it way up to 14 again.
Is this a sign of a bad battery not being able to handle load? Or do I possibly have other electric gremlins?
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Did you charge the battery before you took a voltage reading? A fully charged battery without a surface charge should be 12.66V.
If your battey starts out at 14V then goes to 8V when a load is applied, and then back to 14V, I would take a guess and say that you have a bad battery. But I would also check all battery connections first and then before I condem the battery I would take to a good parts store and have them test it.
Joe
If your battey starts out at 14V then goes to 8V when a load is applied, and then back to 14V, I would take a guess and say that you have a bad battery. But I would also check all battery connections first and then before I condem the battery I would take to a good parts store and have them test it.
Joe
Instructor
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Joe, a quick test to see if your battery is good is to put jumper cables on the + and - terminals of the battery and then touch the other end together and see how big of a spark you get. If it is a wimpy spark then your battery is no good, if its a big spark your battery has good amperage. Then look elswhere for bad connections. Make sure you do this with out the battery terminal connected to car just in case the connection on the battery cables is bad. Thats how Ive been checking them. Kc
Le Mans Master
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From: Limerick Pa
Dont do that, a bad battery that is sulfated or has a bad cell produces gas and it can blow up in your face. I think you have a shorted cell in the battery or a bad connection causing the drop. Yank the battery, take it to advanced auto and let them do a load test on it.
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Some of these 'old school' troubleshooting methods are dangerous, hard on the equipment, and often don't tell you anything you don't know already. Disconnecting the battery to see if the car will run on just the alternator is another bad idea....the battery is the 'ballast' for the voltage/current regulation system. A 2-second multimeter test across the battery for 13.8-14.2 V tells you all you need to know.
Instructor
Joined: Feb 2010
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Dont do that, a bad battery that is sulfated or has a bad cell produces gas and it can blow up in your face. I think you have a shorted cell in the battery or a bad connection causing the drop. Yank the battery, take it to advanced auto and let them do a load test on it.
Thread Starter
Instructor
Joined: Jan 2009
Posts: 106
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From: Marietta GA
Fixed!!
Well it turned out to be a bad battery. So I went with the red top. Boy she cranks right up...800 cranking amps.
I think the culprit was a bad voltage regulator. I tested the old voltage regulator and it was allowing 18volts to the battery when the car was around 1200 rpm
.
So I replaced it with the VR715 from autozone and she put around 13.5 volts at 1200 rpm.
SO on I drive until the next lesson is learned. Got to love it!
I think the culprit was a bad voltage regulator. I tested the old voltage regulator and it was allowing 18volts to the battery when the car was around 1200 rpm
.So I replaced it with the VR715 from autozone and she put around 13.5 volts at 1200 rpm.
SO on I drive until the next lesson is learned. Got to love it!
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Joe, a quick test to see if your battery is good is to put jumper cables on the + and - terminals of the battery and then touch the other end together and see how big of a spark you get. If it is a wimpy spark then your battery is no good, if its a big spark your battery has good amperage. Then look elswhere for bad connections. Make sure you do this with out the battery terminal connected to car just in case the connection on the battery cables is bad. Thats how Ive been checking them. Kc
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Last edited by babbah; Jul 15, 2010 at 08:08 PM.
