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Old 11-28-2017, 05:05 AM   #1
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battery draining when driving

new battery replaced the alternator for the fifth time looks to be charging above 13.0 amps then drops below 13.0 to around 12.5 drove to work with lights on down around 12.0 amps on the way home stopped to get gas click, click would not start took the battery home checked with amp probe only 11.5 amps put battery on charger for an hour 12.5 amps took battery back put into the car started right up drove home.Wish I could know were to look for what is draining the battery.On the way home no radio, no lights,wipers. any ideas?
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Old 11-28-2017, 05:09 AM   #2
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Re: battery draining when driving

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new battery replaced the alternator for the fifth time looks to be charging above 13.0 amps then drops below 13.0 to around 12.5 drove to work with lights on down around 12.0 amps on the way home stopped to get gas click, click would not start took the battery home checked with amp probe only 11.5 amps put battery on charger for an hour 12.5 amps took battery back put into the car started right up drove home.Wish I could know were to look for what is draining the battery.On the way home no radio, no lights,wipers. any ideas?
Yes I do have 12.+ volts on the brown wire on the alternator.
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Old 11-28-2017, 07:33 AM   #3
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Re: battery draining when driving

Its going to jump to the conclusion that when you said "amps" in your first post, you should have been saying "volts".

Those values look like they were measured at the battery posts. What is the voltage from the big terminal on the alt to the alt case?
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Old 12-01-2017, 07:56 AM   #4
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Re: battery draining when driving

took amps reading on the big wire on the back of the alternator and it was 12.1
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Old 12-01-2017, 08:18 AM   #5
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Re: battery draining when driving

OK, so how many volts?
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Old 12-02-2017, 06:42 AM   #6
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Re: battery draining when driving

I work with electric motors I was thinking amps , I meant 12.1 volts
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Old 12-02-2017, 09:56 AM   #7
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Re: battery draining when driving

Have you removed and had the battery and alternator tested independently? Have you made sure that the battery can hold a charge with nothing hooked up to it? I start with ruling out parasitic draw when working on loss of charge issues. It sounds like there is little chance of that being the cause but it's easy to rule out. From there ensure that the battery can be charged up and hold a charge and then test both independently and tell us what they are. Have you also followed the charging wire to ensure that it is not frayed or damaged? Have you made sure the the engine ground is good and the alternator is getting a solid grounding connection?
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Old 12-04-2017, 07:26 AM   #8
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Re: battery draining when driving

Update, after bring the battery home and charging it to 12.5 volts then taken it back and putting it back in drove the car home with the lights on shutoff wouldn't start click, click put the battery on charger again didn't get back to work on it anymore till Sunday. hooked up the battery started up fine 14.7 volts gauge stayed there drove around the block turned on the lights gauge dropped some looked like 13.0 shutoff restarted fine. don't know what the problem is with this car! checked the volts on the big wire on the back of the alternator had 14.7 volts.
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Old 12-04-2017, 09:29 AM   #9
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Re: battery draining when driving

If the big terminal on the alt has 14.7V, then it's working right.

There's a big fat wire connecting the alt to the batt. The voltage at the batt should normally be slightly lower than the voltage at the alt (emphasis on slightly: maybe .1 - .2V or so) because as the current flows out of the alt and toward the batt and the load of the car, which is in that wire, there will be some small voltage drop in the wire.

If the batt has some dramatically lower voltage than the alt, then the charging wire is broken. Pretty simple fix.

Just to help square away your mind, voltage in electricity is comparable to pressure in hydraulics, and current (amps) is comparable to flow. Just like you can have very high pressure in a system but very low flow (your brakes for example) or very high flow but very low pressure (the Mississippi River), you can have the same situations in electricity. You can even mentally relate the size of wire to the size of pipe or river channel.
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Old 12-04-2017, 09:33 AM   #10
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Re: battery draining when driving

Definitely sounds like you have a charging issue. Could be that the brown charging wire does not have constant voltage. It is supposed to be a switched 12V. May be possible that the wire is loose in the C100 connector or cut/frayed in the wire harness. If it's not that then you have a bad alternator.
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Old 12-04-2017, 10:22 AM   #11
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Re: battery draining when driving

Could also be if you had the sensing wire (not the 12V switched brown wire) sensing voltage inaccurately. IIRC the sensing wire should go to a post by the battery that a few accessories also go to. It's used to sense the load on the system. The way I was taught the alternator sensing wire is wired is to put it on a junction point separate from the battery because the battery is too large to measure instantaneous useage. It would be like if you only drank water from a single water cooler. One day you were feeling dehydrated and you went to the hospital. Rather then check you for dehydration we just checked the level of water in the cooler. The water cooler gives you an idea but it's not quite accurate.
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Old 12-04-2017, 09:20 PM   #12
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Re: battery draining when driving

I had a similar charging problem that turned out to be an intermittent connection on one of the wires that plugs into the side of the alternator. A replacement pigtail is inexpensive.
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Old 12-07-2017, 10:40 AM   #13
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Re: battery draining when driving

Update 14.7volts coming off the alternator big wire on the back 14.7 on the brown wire and 14.7 on the red wire the gauge looks like 14.7 also. turned on the lights backed out of the garage volts drop to 12.5 or so drove around the block with the lights on stayed around 12-12.5 volts turned off the lights volts climb to almost 13.0 volts turned off the car unhooked the battery ground cable left off over night hooked back up this morning started the car 14.7 volts. I thinking that it's charging okay there must be something drawing when the lights get turned on.
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