nismorx7

I just installed an fd alternator into my s5 fc and im running into a problem. It seems to work great above abour 1200rpm, showing 13.5+, but below 1200rpm it drops off to 12.5 or 12.1 with lights and brakes applied. I have the atkins dual pulley installed.
The only conclusions I can draw are that I may have incorrectly wired it ( I didn't wire a thing, just plugged it in because its LS to LS), I have a wonky regulator, or the pulley is too small.
I need advice though, any thoughts? Was I supposed to wire it a different way?

nismorx7

I read up on the wiring and there were no mods to be done, so that cancels that.
I have a power fc, and a large efan as my only load sources, no stereo. I'm wondering if the fan alone could be the culprit, but I assumed the fd's output would handle it.

1SxyRXy

bad alternator?

misterstyx69

iTrader: (142)

Mine does the same thing.it is on my S4..Parked or stopped at idle my lights are Dim,but touch the gas,they get brighter.I can cruise at 14.5 volts,no problem.
I am thinking Regulator.I am close to an alternator rebuild place to I may take it there.

nycgps

iTrader: (4)

So does that mean FD's Alternator is direct drop in to S5 with no modification at all ?

cuz I think my S5 Alternator is dying, charging only 13.6-13.8 with headlights on.

sharingan 19

iTrader: (16)

yea, its drop in for S5.

The FD alt doesn't charge too well at idle, but it should still put out close to 13V over about 900-1000rpm (where the vast majorityof driving is done) it should be putting out 13.5 easily, I get 14+ at pretty much anything past 1200-1500rpm

nycgps

iTrader: (4)

well, stock FC NA S5 @ idle is like what, 650 or 700 something RPM? thats kinda low IMO

I can go for other ones but for me, FD Alternators are easy to get

Thx

jackhild59

iTrader: (7)

Is that Atkins pulley an underdrive pulley?

farberio

iTrader: (7)

+1. I was thinking the same thing.

atsugiT2

iTrader: (1)

sorry to revive a thread from so long ago, and i know its been said that its a drop in install on the s5, but does that also mean no belts, pulleys, etc are needed? if i bought just a fd alternator would i have everything i needed for the swap? and if so, im in the mnarket for one.
thanks in advance,
carrington

misterstyx69

iTrader: (142)

since the FD pulley is a serpentine design you need to change it to a V groove belt pulley.
The bore is 17mm.(shaft size)

atsugiT2

iTrader: (1)

thanks boss