Underdrive pulley gimmick!
 

I searched the archived threads and couldn't really find an answer to my secific question. I've got March U/D pulleys and my battery is constantly dead when the car isn't started for 3+ days......the lights dimming at idle (@ night) is also a pain in the arse. I'm planning on getting a Optima red battery soon......and thinking about putting the stock pulleys back in.

Do you think I'll be OK w/ just the Optima w/ the UD pulleys, or do I REALLY need to step up to a 130-140 amp alternator if I keep them in (I'm not into stereos either). I'm thinking that losing possibly 5hp might not be as bad as spending the $200 on a new alternator.

I've only read about the 5+hp gains in the mags......and I've honestly never witnessed that gain in person at the dyno. I have seen a 2rwhp gain on a moderately modified stang (heads, intake, cam, etc etc), but that's not really noticeable at all.

Any thoughts?

check for any battery drains while the car is off. If I remember this correctly you can do it by disconnecting your negative battery cable, then using a test light hook the test light wire to ground and touch the test light to the negative battery terminal. If it lights up something is draining the battery. I had this problem and it turned out to be my alternator regulator.

i dont know why everybody thinks the 130 amp alts. are 200 bucks. go to autozone and pick up an alt from a 94 GT. they are only $90. and a peice of wire is maybe $15. and a fuse for $10 with a holder. so for maybe 125 or less you can get the alt and everything you need for the swap.
you can run the alt without using a fuse for a while if want, i have but i dont recomend it.

that is all you need, you wont need a battery (if you know yours is good).

take care,
adam

OK, I'll do a test to see if there's a drain from somewhere. I'll probably need a new battery because mine has died and been recharged coutless times. So, are the u/d pulleys really worth keeping anyway?

i personally dont have them but i have heard some great things as well as some terrible things about them. i have heard 4 tenths off an E/T (which makes me want to get them) and stuff like they cant keep a charge at all and overheating.

i think if you get an alt (if you dont have a currant draw somewhere else thats draining it) you will be more than satisfied.

take care,
adam

Let me play Devil's advocate.....

Get your battery checked. Otherwise with no shorts, good battery and alternator/regulator etc.....

Why would you need a higher output alternator, unless you're really pulling a lot of juice to operate additional equipment? It's working fine, except at idle, correct?

Your problem seems to be at the low end of the RPM range, (dimming lights). An alternator has to get up to a certain speed to maintain a given charge to overcome the load, doesn't it? The original pulley size is designed to give you that alternator speed at idle. Once you change the pulleys, you've automatically reduced the low end (idle) charge rate.

A higher amp battery may help with the head light situation for a while, but at extended idle, the same dimming will occur, won't it?

I'm gonna have to say that you have a drain somewhere. Either that or your battery is no good. I would recommend keeping the pulleys because thats not your problem. Most of the people on this board have pulleys, and it is true that some can slow your alt down enought to make the car not charge at idle, but you should have plenty of juice left over from acctually driving the car around. Check for a drain and go have the battery tested... keep the pulleys thouhg.

RE: Devil's Advocate
 

While you're kinda correct, you're assuming that both the 65amp and the 130amp are at least linear in their power production at idle. The stock 65amp alternator could be putting out as little as 15amps at idle, where the 130amp can make 60. The G3 alternator also uses a larger diameter pulley than stock 65amp alternators. If you were to take a used alternator from a 94-95GT and put it onto an 86-93 GT, you'd have a slight underdrive effect right there. I see no logical reason to run a fuse on the alternator if you wire it properly. The 94-95GTs use the 130amp without a fuse, why would you have to put one on a fox?

By the way, I have a 130amp alternator, and it charges with the rear defrost, max A/C on high, headlights and foglights on at idle. About 14.0 volts last I checked.

change the alt. pulley back to stock
 

I had the same prob. I just changed the alt. pulley back to the stock one and the problem went away.I called march and they said with a auto tranny I needed to run the pwermaster pullies(aka the ones for the stereo crowd.They said some 5 spd cars also have this problem .Good luck!

I was always having charging problems with my car. It would be fine driving but when id stop at lights with everything going the volt gauge would start to drop. I just bought a powermaster 1 wire 100 amp alt and i havent had the problem since. The alt was 250 cdn and i had to do a little customizing to get it to fit properly(i got the chevy alternator) and i had to run a power wire since its the 1 wire. And if i had to do it again id do it in a sec.

Thank you all. I'll let you know what happens.

avbcon12.......what autoparts store did yu see the 130amp alt for the 94gt at for $90??? I jus called my local carquest and they told me it was $176 and I'd have to go to Ford for the wiring harness. Would I even need a new wiring harness?

autozone, i just boght one a month ago. it was $90. you dont have to get any new wiring harness for anything. do a search on the internet and you will find many "install" write-ups. heres one: http://www.mustangcentral.net/tech/alternator.html

take care,
adam

Thanks Adam.

sure thing, take care.

adam