Alternator Question

Alternator Question

Postby Chug » Mon Jan 13, 2014 10:07 pm

Ok, I have been noticing an issue with the Indy. It seems that when I have some accessories on in the car (headlight, heat and wipers) that when it gets to 900rpm/idle my voltage drops to 11v, according to the gauge. I believe the gauge because the headlights get dim when the gauge drops. When the rpms increase, by just a couple hundred, the voltage is back around 14v.

My question, is this typical in the 4cyl auto or is there a fix for this?
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Re: Alternator Question

Postby Trinten » Wed Jan 15, 2014 7:45 am

Hey Chug,

I think that might have to do more with the alternator and the voltage than the 4cyl itself - I thought that most alternators don't put out full voltage/amps until they get to like 1100 RPM or something, so what your describing sounds like correct (if a little annoying) behavior. Maybe stepping up the alternator would help, because at lower RPM it might still put out more juice than the stock one?
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Re: Alternator Question

Postby Chug » Wed Jan 15, 2014 11:11 pm

wonder if I can change the pulley to a smaller one to make the alt spin faster at lower RPM. (If there is a smaller one to be had)
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Re: Alternator Question

Postby Drew-py » Sat Jan 25, 2014 4:37 pm

Chug you know I have been chasing this in both my Super P and its twin forever now, its seems to be in your 2.5 both my 2.8 and 3800 and didn't Trinten have an Alt issue with his V8. Mine acts just like yours <900 RPM's low voltage >1000 RPM's good voltage. Is it an Alt problem or a command issueto the regulator, i shall follow and this for help also
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Re: Alternator Question

Postby Trinten » Sun Jan 26, 2014 3:43 pm

Yeah my alternator issue though was a combination of a bad alternator, and not enough tension (belt slipping around the alt pulley, hence lower RPM for the alt, and lower output). That was the drawback of the belt setup I used to have.
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Re: Alternator Question

Postby CowsPatoot » Tue Feb 11, 2014 11:32 pm

I know I am late to this...but...

I had the same issue in the vert...combined with excessive belt squeal regardless of how tight the belt was. I noticed it was at its worst when the HVAC fan was on. Then I found out the HVAC fan draws close to 20 amps by itself. I had an alternator from an 85 GT in mine...but found out it was still only a 74 amp alternator.

My solution was to do a CS130 upgrade. I installed a stock alternator out of an 88 GT. It was as simple as swapping the pulley and pigtail on the harness. With the auto, you will have to remove the upper alternator bracket...don't try to remove the lower, those bolts also hold the engine mounting bracket.

With the CS130 alternator, all my electrical issues are solved. I notice no drop in voltage at any RPM, and the belt squeal is completely resolved as long as I have the belt tightened properly.
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Re: Alternator Question

Postby Chug » Wed Feb 12, 2014 12:31 pm

So the answer is a 88 GT V6 CS130 Alt on my 4cyl should correct the issue? Just wanting to clarify.
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Re: Alternator Question

Postby CowsPatoot » Wed Feb 12, 2014 2:11 pm

Correct....don't forget to grab the pigtail for that while you are at the parts store.
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