Question about 1985 Ford Mustang

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I have a 85 mustang gt and the battery will over charge when i drive it .put in a new bat,voltage reg,alt,bat cables .need help!

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They sell stabalizers around 30.00 it should drop voltage to 14.5 can find on ebay

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You would think that the problem would be solved after changing all of those parts!

The voltage regulator should keep the voltage below a certain level. Even though you changed that, I would be suspicious about the quality of the part.

I would try another brand of voltage regulator.

Have the starting and charging system analyzed at Walmart or your local parts store to see what it charges at under load.

Good luck to you.

Posted on Jul 04, 2010


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Does the ECM control the alternator charging amperage/voltage on a 2004 Suzuki aerio? New alternator only charges @12.5. Won't charge enough to keep ahead of necessary power draw.

Some vehicles are fitted with a smart charging system that is designed to prevent the alternator charging during acceleration to free a few horsepower to help.

My experience of these is very limited but there is an ECU that controls them and the battery, charging or ignition light using information from the engine management system.
The alternator generally has an extra plug with about four or five wires which when disconnected render the alternator a standard machine sensed type.

Japanese vehicles used separate voltage regulators longer than most types. You either need experience or a wiring diagram for good fault diagnosis but mostly it is unnecessary to check the charging current of an alternator which bears little significance unless being tested with a graduated load or adjustable carbon pile.

The current output of a healthy alternator is dependent on the terminal voltage of the battery which in turn is dependent on the electrical load placed upon it. Switching on the lights should lower the voltage and increase the alternator output. If the battery is particularly good the voltage won't fall very much and the current won't increase as much as expected...

Measuring the battery voltage with the engine running at about 2000/2500 rpm is sufficient for most purposes. With nothing switched on and a fully charged battery it should be around 14.5 volts and with everything switched on (lights, HRW, heater fan, etc.) a healthy alternator should continue to maintain a voltage above that of a healthy fully charged battery (13.2 volts).

If the voltage isn't maintained on load the charging system, probably the alternator, is faulty and should be independently tested.

Jan 25, 2017 | Suzuki Cars & Trucks

2 Answers

Put a new alternator and battery on the truck but still does not charge

Hi George,
I need year--make--model--engine size.
Usually the alternator needs excite voltage or no charge. The alternator bat terminal should be hot all the time, even with key off, if it isn't, something wrong with that wire circuit.

Mar 04, 2016 | Cars & Trucks

1 Answer

Bad eld wire or ecu?

Sounds like the alternator is charging, but the extra voltage is not reaching the battery. You should have battery voltage on the large wire at the alternator with the engine off.
If not, that wire is fried or a fuse is blown.

Jul 07, 2013 | Cars & Trucks

1 Answer

1983 ranger voltage regulatar problems, when mount amp light comes on when not mounted amp light stays off. new alt.-v reg, bat., .evrything tested good. Bat. dies if truck sits for about four days

You have a short someware . Try this test disconnect the negitive cable from the battery. Take a multi meter set to 20 volts DC .Go from the positive termenial on the battery red to the engine block or a known good ground point. See what you are reading for voltage it should be zero or vary low do to static electricty if its 1or2 volts then it could be a light or a hot wire touching the body you can see what you are haveing any kind of problems with electrical also check your main ground cables they tend to rot out on this vehicle i know i have on 85 ranger the jacket will look fine but the wire inside it rots out and leeds to all kinds of problems . If the voltage is higher around 5 volts or so then its a motor but it would likely kill the battery in a day or less not 4 days . You can start pulling fuses one at a time to see if the short goes away to pin point witch curicut the problem is on

Jun 28, 2011 | 1983 Ford Ranger

1 Answer

Alternator wiring im trying to by pas a volt. reg. to charge a bat. witch wire do i splise strait to the bat. for charge

you dont slice any wire to the battery. the alt is turned on by grounding the green field wire on the back of the alt.THIS IS FOR TEST ONLY if you leave it grouned and drive it you will blow up the battery from all the hydrogen gas created by the massive overcharge. you also will damage every computer in the car from the overvoltage they will recieve.
the engine computer is the regulator for the alt.

Mar 20, 2010 | 1996 Plymouth Voyager

2 Answers

Not charging 1980 ford truck not charging drains batterie in 10 min.has new bat,new voltage reg

If you had the battery cables on the battery and plugged the regulator in before you bolted it to the truck then i can guarantee that the voltage regulator is ruined.If this is not the case then you need to check for a drain,put a test light on the battery negative[with the cable off of the battery] and then put the tip of the test light on the negative post.If it lights up you have a drain.Start unplugging stuff,start with the regulator and the alternator,if the light does not go out then start pulling out fuses until the light goes out,that will be the circuit you need to look at.Let me know how you make out.What ever puts the light out is the circuit or the component with the problem.

Jan 08, 2010 | 1982 Ford F 250

2 Answers

What will cause a 1999 dodge diesel not to charge?? I have put new alt. on it and checked everything i know to check

How old are your batteries ? Diesels take a lot of juice to turn them over, I had a similar problem once, turned out to be the positive cable leading between the batteries.I would get a diagnostic on it to confirm your problem, could just be something simple.

Sep 01, 2009 | 1998 Dodge Ram 3500 2WD

3 Answers

81 bronco, 351w. alternator is creating charge, but not sending it to the battery, after new voltage regulator.

if you have charge out put at the alt but none at the batt. then your problem is in the wiring

Aug 19, 2009 | 1981 Ford Bronco

2 Answers

Need help with 1994 Dodge Ram Charging system Repair

FULLY CHARGE BATTERY BEFORE USING.If you dont you will burn out the alt. within minutes.
Does the new alt have all the same connections as old one?
After charging bat and installing new alt. typical battery load test and alt. output test should tell if there may be other problems.

Jun 23, 2009 | 1994 Dodge Ram

4 Answers

Put a new alternator in 2000 Jeep Grand Cherokee engine light on

well , the ECU runs the alternator. (DG wire "dark green")
the alternator field is controlled 100% by PCM reg , inside PCM.
so..... if the running engine has 13.3, to 15vdc the alt is working
if lower, its not. (rpm on engine 800 or more)

not scanning the PCM a the CEL glow, you missed the boat.
why not scan it. see why the PCM is upset (DTC errors stored)

see the 2 lower pins below , those go to PCM.
in theory if the field in the old BAD ALT, was shorted.
that could in fact, burn up the PCM regulator.
shorting outputs of PCM , does that in most cases.
im the poor sod that fixes PCM'


Apr 07, 2009 | 2000 Jeep Grand Cherokee

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