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Author
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Topic: engine dies
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GRLPNY
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Member # 2626
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posted
 
 
Lately any time I have my air conditoner on or my defroster on full blast and come to a stop at a light the car dies and the battery voltage drops into the red. I was wondering if my battery isn't strong enough to run the AC or if its something else?
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1989 Mustang 5.0 GT
Cold air kit, throttle body, maf sensor,exhaust, and 3.73s
Posts: 39 | From: East Bay | Registered: Mar 2003
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94gt
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Member # 3060
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posted
your altenator could not be charging it correctly. take a trip to kragens and they will run a test on the electrical system for free. ![[patriot]](graemlins/patriot.gif)
or you could just pull off the positive cable off your batt while its running and see if it dies.
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2020 Explorer ST
2011 Silver Raptor 'Screw
Posts: 5777 | From: Beavercreek, OH | Registered: Jul 2003
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GRLPNY
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Member # 2626
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posted
does that mean the alternator is going bad... i replaced it when I first got the car about 9 months ago
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1989 Mustang 5.0 GT
Cold air kit, throttle body, maf sensor,exhaust, and 3.73s
Posts: 39 | From: East Bay | Registered: Mar 2003
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wilit
Mustang Messiah
Member # 3367
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posted
quote:
Originally posted by 94gt:
or you could just pull off the positive cable off your batt while its running and see if it dies.
DO NOT DO THIS!!! It was an old school trick for old school cars. If you try this, you run the risk of frying the ECU. Not a good idea.
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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94gt
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Member # 3060
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posted
how?
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2020 Explorer ST
2011 Silver Raptor 'Screw
Posts: 5777 | From: Beavercreek, OH | Registered: Jul 2003
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wilit
Mustang Messiah
Member # 3367
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posted
quote:
Originally posted by 94gt:
how?
The voltage regulator sees a massive drop in voltage, so it compensates for it by supplying more voltage to the system, but since there's no battery to absorb the extra power, the entire electrial system gets a big fat voltage spike. Granted, you're not necessarily going to fry the computer every time you do it, but you do run the risk of it happening.
In old cars, it's not a real problem since there aren't any electronics on board.
[ March 22, 2004, 03:48 PM: Message edited by: wilit ]
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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94gt
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Member # 3060
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posted
quote:
Originally posted by wilit:
quote:
Originally posted by 94gt:
how?
The voltage regulator sees a massive drop in voltage, so it compensates for it by supplying more voltage to the system, but since there's no battery to absorb the extra power, the entire electrial system gets a big fat voltage spike. Granted, you're not necessarily going to fry the computer every time you do it, but you do run the risk of it happening.
In old cars, it's not a real problem since there aren't any electronics on board.
not to argue but a cars typical voltage range is usually on or around 12vdc. The voltage regulator's job is to reduce a higher than expected voltage signal to the required voltage for the car (12)
The altenator and battery work in tandem to make sure enough amperage gets to the needed components. If suddenly high current demand presents itself and there's not enough amperage to go to the needed system, the battery pics up the slack, and then is recharged by the alt.
Im assuming that you are talking about a load spike destroying the ecu, I would see that happening more from an altenator over-charging (supplying too much load) rather than not enough.
a similair thing happened to me when my serpentine belt broke, with the alt no longer supplying electrical current, the car ran like sh*t because it was drawing an large electrical load from the battery.
easy way to troubleshoot, let kragen do it for you
or the harder way, bust out a mulimeter ![[Razz]](tongue.gif)
[ March 22, 2004, 04:04 PM: Message edited by: 94gt ]
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2020 Explorer ST
2011 Silver Raptor 'Screw
Posts: 5777 | From: Beavercreek, OH | Registered: Jul 2003
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BlackNGold
CaliforniaFords.com
Moderator
Member # 655
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posted
quote:
Originally posted by GRLPNY:
does that mean the alternator is going bad... i replaced it when I first got the car about 9 months ago
Make sure you get the battery tested as well as the alternator...If you replaced the alternator while keeping a half ass working battery, it could be working your alternator too hard and causing it to prematurely brake....
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-SLOWER TRAFFIC KEEP RIGHT-
Posts: 5132 | From: Bay Area, CA | Registered: Dec 2001
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wilit
Mustang Messiah
Member # 3367
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posted
Sorry, I re-read my statement, and it is a little unclear. When you disconnect the battery on a running car, the voltage regulator sees the drop. All of those points you brought up are 100% true, and I'm not going to disagree, but when the alternator increases it's output due to the sudden loss of the battery, that's when it spikes it's output, and since the battery is not connected to absorb both the voltage and amperage spike, the rest of the system has to absorb it.
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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