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Old 07-22-2014, 12:31 AM   #1
68coupeWA
 
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Default 68 Mustang Charging Problems

Hi there,

I am having issues with the charging system on my 68. I have replaced the alternator (which I have had tested), I have replaced the external regulator with 2 different new ones, and I have had the battery tested. The battery seems to hold a charge overnight but when I run the car and rev the engine, it is only producing 12.2 volts.

Any ideas out there? The only thing I can think of is to replace the wiring harness on the alternator.
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Old 07-22-2014, 01:00 AM   #2
67mustang302
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Sounds like wiring.
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Old 07-22-2014, 08:10 AM   #3
Mach428
 
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Default You didn't say how many amps the alternator is putting out

or what electrical devices are on when you're running the engine. It could be that your good alternator is putting out as much as it can but cannot keep up with the demand.

I had this problem with my 428CJ and finally replaced the alternator with a one-wire Powermaster. No more problems.
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Old 07-22-2014, 11:24 AM   #4
bop11
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Do you have a black ground lead going from the alternator to the block, and to the regulator attachment bolt? Is that wire broken? You need to ground the regulator and not rely on the sheet metal.
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Old 07-31-2014, 09:02 PM   #5
billyg37s@me.com
 
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[QUOTE=68coupeWA;8410839]Hi there,

I am having issues with the charging system on my 68. I have replaced the alternator (which I have had tested), I have replaced the external regulator with 2 different new ones, and I have had the battery tested. The battery seems to hold a charge overnight but when I run the car and rev the engine, it is only producing 12.2 volts.

Any ideas out there? The only thing I can think of is to replace the wiring harness on the alternator.[/QUOTE

I went with the power master 100 amp one wire ran 10 gauge from alternator straight to the positive side of the battery even with coated march performance pulleys it didn't need a ground she is charging at 14 and change and I couldn't be happier loosing the voltage regulator as it is integral in the alternator now think I paid around 180 and the optima red battery makes a nice addition as well
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Old 08-01-2014, 08:48 AM   #6
bop11
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Insure you do the resistance check as in the instructions between the alternator case and the negative battery terminal.
With your installation, what engine speed do you need to turn the alternator on? Typically it is 1200 alternator RPM, which, with a 3:2 diameter crank to alt. pulley ratio, would be about 800 engine rpm.
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Old 08-01-2014, 09:27 AM   #7
Chromeshadow
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Quote:
Insure you do the resistance check as in the instructions between the alternator case and the negative battery terminal.
Just saw your location, dampness on an older car over time causes a lot of corrosion. The resistance check may find your problem. Most hand held meters are not very good at measuring low resistance, if you touch the meter leads together when you turn it on it should calibrate to take out the resistance of your meter leads.
It's possible to measure voltage from the alternator case to the output lead on the alternator when running, make sure to use jumper clips-don't hold your hand in there when the engine is running. If this reading is about 14V, your alternator is fine, you have a poor connection somewhere. Don't assume that metal to metal connections are good. The ground post on the battery has to have a really good path to the case of the alternator.
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Old 08-01-2014, 03:58 PM   #8
barnett468
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hello

pull the plug off the alternater.

connect volt meter to battery

start car.

connect the A and F posts/wires on the plug with a paper clip or wire and check voltage.

if there is no change then rev the engine.

if there is no change the alt or wire harness is bad or the alt is incorrectly connected.
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Old 08-01-2014, 03:58 PM
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