1990 Mustang 5.0 lx.. 3G alternator install help. - Ford Mustang Forum
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post #1 of 20 (permalink) Old 05-25-2007 Thread Starter
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Thumbs down 1990 Mustang 5.0 lx.. 3G alternator install help.

I did a 3G 130 amp alternator install today, followed the instructions to a "T", it all went smooth, even the "work" on the bracket.. Problem is, it behaves just like the 2g, for the most part anyhoo, it seems to get to a normal charge level quicker, but at idle, 650 rpm or so, it still goes below 12v, with NO accessories running. I really want to get this to working properly, as I am gonna put an electric fan in.


What could this be? I doubt it's the alt, b/c it does well at 1300rpm and up.

My underdrive crank pulley is tiny.. I have had a few people look at it in disbelief when they see its size, it was on when I bought the car..Does the underdrive pulley really do all that much?

Will I have to change a pulley on the alt, or maybe acquire a larger crank pulley? If that is the case, does anyone have one they are willing to sell?

thanks for the read, and any advice...

Grover
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post #2 of 20 (permalink) Old 05-25-2007
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Maybe u have a pretty hardcore race pully on your crank, that would slow it down. Try getting a street pulley set from BBK or March. Is it a new alternator, some times the regulator bites it..

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post #3 of 20 (permalink) Old 05-25-2007 Thread Starter
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Brand new alt.. Decided to go that route, for the warranty.. I'll have to do a little lookin to find out exactly what pulley it has.. i can take a photo of it tomorrow, when theres some light...

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post #4 of 20 (permalink) Old 05-25-2007
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My 3g at 850rpm puts out 14.5volts and 62amps at idle and that is using a normal size under drive pulley.

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post #5 of 20 (permalink) Old 05-25-2007 Thread Starter
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thats the kind of output I am expecting... It gets frustrating sittin in a drive thru or in traffic, and the battery gettin drained...

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post #6 of 20 (permalink) Old 05-25-2007
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95-02 FORD LINCOLN 200 AMP HIGH OUTPUT ALTERNATOR 7773: 7773-200 AMP DB Electrical Starter-Alternator?

HINT>
For safety, we recommend replacing your main charging wire to a
4 gauge cable to allow maximum charging current.

:eyepoppin
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post #7 of 20 (permalink) Old 05-26-2007
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also what pulley are you using on the alternator itself. im using a pulley from a 94 GT and its pretty small, maybe about 2.5 od. the V6 pulleys are a bit larger.

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post #8 of 20 (permalink) Old 05-26-2007
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That alternator probably has a 1 wire hook up, or at least can be done with the 1 wire. If that's the way it was connected, it won't kick in until the charging system needs it, which is not something I like to do. I had that problem and re-did the wiring to retain the factory style 2 harness connections. Do you have that? If not, try it and see if that helps.

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post #9 of 20 (permalink) Old 05-27-2007 Thread Starter
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Quote:
Originally Posted by mustanghelper View Post
HINT>
For safety, we recommend replacing your main charging wire to a
4 gauge cable to allow maximum charging current.

How would one do this? Do I just run a cable from the post on the alt to the positive terminal?


Quote:
Originally Posted by lxarlo View Post
also what pulley are you using on the alternator itself. im using a pulley from a 94 GT and its pretty small, maybe about 2.5 od. the V6 pulleys are a bit larger.
It has the pulley that comes stock on the alternator, I bought one designated for a 95 GT.

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Originally Posted by EagleAutosports View Post
That alternator probably has a 1 wire hook up, or at least can be done with the 1 wire. If that's the way it was connected, it won't kick in until the charging system needs it, which is not something I like to do. I had that problem and re-did the wiring to retain the factory style 2 harness connections. Do you have that? If not, try it and see if that helps.
Yes, it is a single output post on the back of the alt. I still have the 2 wire harness in my trunk, I cut it off like the instructions said to, How would I go about doing that..


Oh yeh, here are the pics of my crank pulley.
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ya thats way to small for a street car. Thats for a track only car.

Id swap it out with a venders streat version.

j

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Quote:
Originally Posted by grover175
at idle, 650 rpm or so, it still goes below 12v
It should be no wonder why voltage is dipping that low at that RPM. Idle RPM should not be that low.
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A SMALL crank pulley will turn all the other pulleys FASTER, unless those pulleys are larger, in which case it evens out.

LARGE pulley = underdrive
SMALL pulley = overdrive
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Wow, that's a tiny crank pulley, I'd say that's your problem right there.

The easiest way to run a one wire hookup is to get a good size wire, and solder ring terminals on both ends, and run it from your alternator to the hot side of the solenoid. I recently put in a new power master 100 amp alternator, and that's how i did it. I think 4 gauge wire may be a little bit of overkill. The instructions for my alternator called for a minimum of 10 gauge, I used some 8 gauge that I bought at Lowes.

The one wire hook up alternators won't switch on till the engine reaches 1500 rpm or so when the engine is first started, but will remain "on" after that till the engine is shut down. I am using the one wire hook up with no problem, and can see no reason to go back to the three wire hook up.

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Quote:
Originally Posted by FoxChassis View Post
A SMALL crank pulley will turn all the other pulleys FASTER, unless those pulleys are larger, in which case it evens out.

LARGE pulley = underdrive
SMALL pulley = overdrive
Hate to disagree with the master, but in this case I think you're wrong.
A small crank pulley has to turn everything else slower, think about it.

A small pulley on the alternator will drive the alternator faster, because it's the driven pulley, but it works the opposite on the crank pulley which is the drive pulley.

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Yeah, you're right. Don't know what I was thinking there. Got ahead of myself and just blurted it out.
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