Charging problem, Alternator, Battery, or what? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 9 Old 09-30-2002, 01:11 AM Thread Starter
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Charging problem, Alternator, Battery, or what?

Today after church, I noticed my volt meter gauge was low(on the "n" and "o") and then halfway to the gas station it poped back up to normal(at the "m" and "a").
I checked the battery and it had 12 volts when off, The alternator had 12 volts when it was off, When I turned it on the alternator had 11.6 volts, reved it up and it stayed at 11.6 volts. Think its the voltage regulator on the Alternator? NOBODY MAKES GOOD RELIABLE ALTERNATORS!!!!!!!!!!! This is my 3rd!

Thanks for your help


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post #2 of 9 Old 09-30-2002, 12:57 PM
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I'd say it's the alternator. When the car is on you should be getting around 14 to 14.5 volts at the battery. My guage did the same thing when the alternator went bad.
As far as getting a replacement from the local auto part stores, it's hit and miss.
If you don't want to waste your time, I'd purchase a new one, not a rebuilt one. While your at it, get a larger one than stock. A 130amp one will work fine with minor modification to the bracket, and wiring. Check the tech section under mantainence, 130A 3G alternator upgrade.

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post #3 of 9 Old 09-30-2002, 02:33 PM Thread Starter
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Thats what comes on a 1994 Mustang Cobra Stock.

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post #4 of 9 Old 09-30-2002, 08:34 PM
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Before you go out and get a 4th alternator, make sure all your connections are clean and tight: the battery connections and the lug that connects to the alternator stud and all the connections at the starter relay. A poor connection can cause the same symptoms. Test all your voltages with the engine running and with as many electrical items ON as possible. This puts a load on the alternator and any bad connections will show up as a voltage drop. You should see no difference in voltage from negative (battery post or vehicle body) to positive (all those listed above).

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post #5 of 9 Old 10-02-2002, 05:20 PM
 
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My voltage gauge reads lower as the engine bay heats up. When I start off the gauge reads "R". After a while of stop and go driving the gauge drops to the "O-N". I've tested the before and after with a volt meter and I'm getting 14.6vdc cold and 12.4vdc hot. I've so far replaced the damn regulator, AND alternator. What the hell could this be??? The battery? I know my computer is bad, would that have anything to do with it????? HHEELLPPP!!!!!!!!!
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post #6 of 9 Old 10-02-2002, 08:58 PM
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The regulated voltage DOES decrease with increase in temperature, this is normal. If the alternator gets too hot, for whatever reason, it won't destroy itself.. It shouldn't drop below 13V. If you have a '94, it's a 3G; you didn't say where you got your replacement. There's a lot of junk automotive electrical and hard to tell what's good and what isn't. I couldn't tell by looking at it and I'm an electrical engineer.

It could be your computer; if you could measure the current draw from the alternator (a DC clamp meter will do the job, if you can borrow one), you would know right away what's happening. No alternator can put out full load current for very long. The higher the load, and the longer it runs, the hotter it will get, so maybe the regulator and alternator are fine and trying to tell you something. A 130A 3G has a continuous rating of 80-100A. The lower end in the summer and the higher end in the winter.

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ProCharger P600B, FRPP Headers, Flowmaster F2, 3G Alt, Mk8 Fan/DCC, 3.55's, Prog Springs, ST Brace, G/Trac Bar, Subfrms, UCA, LCA, FCA, Tokico 5-ways, C/C Plates, CSA 16x8, Bridgestone RE760 Sport 225/50R16, Megasquirt DIYPNPF60, LC2 WBO2, C&L76mm MAF w/LU47's
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post #7 of 9 Old 10-04-2002, 01:54 PM
 
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Quote:
Originally posted by Blown88GT
The regulated voltage DOES decrease with increase in temperature, this is normal. If the alternator gets too hot, for whatever reason, it won't destroy itself.. It shouldn't drop below 13V. If you have a '94, it's a 3G; you didn't say where you got your replacement. There's a lot of junk automotive electrical and hard to tell what's good and what isn't. I couldn't tell by looking at it and I'm an electrical engineer.

It could be your computer; if you could measure the current draw from the alternator (a DC clamp meter will do the job, if you can borrow one), you would know right away what's happening. No alternator can put out full load current for very long. The higher the load, and the longer it runs, the hotter it will get, so maybe the regulator and alternator are fine and trying to tell you something. A 130A 3G has a continuous rating of 80-100A. The lower end in the summer and the higher end in the winter.
The alt I bought was a rebuild unit from my local parts store. I know that there is junk out there but this one came with a 1 year warrantee, had a "spec" sticker from a tech inspection on it also. I would think that if it was garbage then it would atleast work great the very FIRST time I installed it. I know that the alt will "protect" itself when it gets too hot, but the computer is pulling a code "511" which means the EEC is bad, replace. Your saying that the computer could be causing this? I hope so since I have to replace it anyway!
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post #8 of 9 Old 10-04-2002, 02:20 PM
 
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double check ur wires at the selinode (sp?) when my alt went bad it burned one of the wires (a fuse wire) & didnt know it; replaced 2 alts before checking the wires
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post #9 of 9 Old 10-05-2002, 12:22 AM
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check your alternator energizing wire it is the one wire white plug at the back of the alternator. if this wire is giving the alternator the proper voltage the alternator can have your symtoms. check the resitance of that wire, it could be coroded internally as i have seen this happen on my buddies car.
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