Funny Alt problems.

[Legendary]

I think my car has been running on the battery for the past couple of days. The Alt gauge is low and the needle doesn't move when I rev the car up. I also notice the electric fan isn't spinning full speed either. Well today I got in the car and the alt seemed to be charging just fine. The needle was responsive and showing a charge. After driving for about 10 mins the needle dropped back down and started to not charge again. I checked for loose wiring and everything.

I never had an alt to go out and then come back when it was cold. Is this an alt problem or more of a wire shortage? I have the 3g up grade and the 4 guage wire looks fine. I have noticed that when I turn the ignition on (without starting the car) I don't get the usual battery light that is displayed just before cranking over.

 

[STINGREY]

sounds like the alt may need replacement,the diode pack could be kicking in and out.

 

[5spd GT]

Well I'm killing myself right now trying to figure out what the wire is called because I had a similar problem and had a mechanic mess with it after I replaced the alternator (3g) and it didn't do anything...

Well anyways...my battery light came on one night and I didn't think nothing of it...and well the battery guage "bar" kept getting lower and finally it got so low that my car had absolutley no power (I went to pass a vehicle on the way to school) and I couldn't get around them...it started popping...and the car finally died on me so I literally rolled into an Animal Hospital and walked to college (it was only 1/5 of a mile probably)...I put in a new battery to get home and took it to a mechanic after I put in the new 3g alternator and found out it was still running off the battery...the mechanic replaced some wire (I guess because of a shortage)...and all is well

I was thinking it started with an "A" and no it's not alternator wire ...

 

[Legendary]

Was this wire inside the alternator?

 

[jrichker]

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-90 wiring

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

 

[afast93stang]

Im actually having what sounds like a similar prob, only when my needle droped it didnt go back up at any time when I was driving...

 

[5spd GT]

Was this wire inside the alternator?

I don't know man...the mechanic gave me the below description...I can almost guarantee you it wasn't "in" the alternator...

Here is the description the mechanic gave...He said that "it is the wire that tells the battery that the alternator is going to take over control now" so whatever that is?

 

[bgjohnson]

okay here's somthing to consider, that when you have heat go up, so does resistance in the wire, and they have somthing that regulates the amount of voltage that is sent to the alternator to create the magnetic field, yes your alternator uses a current to produce one. so if after heating up maybe this regulator isn't telling it to turn the alternator on, ooor the brushes or commutator are bad an not getting a good connection to produce a current.

 

[jrichker]

See http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif -look at the alternator low battery light in the lower RH corner of the diagram. If this wire gets broken, the alternator will not charge properly.

 

[mustangsquared]

I had similar problems with my 3G...I then started killing Starter relays because the low voltage was causing the contacts to weld together during starting (took a couple days each time)...I replace the battery to starter relay with a 2 gauge, the negative battery post to block with a new 4 gauge. Double check your alt to starter relay cable (MUST be al least a 4 gauge) for good connections. Once I replaced those cables and the starter relay....16 volts at battery (just above the middle of the gauge...never drops below that middle mark on gauge by more then a mm or 2, even with the elect fan, AC, lights, and radio on at once sitting a light). Try it. Your wires are probably original and could use being replaced anyway and may save you time and fustration.

 

[Legendary]

Well all my power cables should be fine. 4g for the alt and 2g for the battery that goes in the back. It's all new cables. I'm going to take the alt off and get it tested today. I'm sort of hoping that it's the alt. I hate to have to track down a wire gremlin. I will test the 'alt light' wire too while I'm at it.