Trueno102

iTrader: (1)

I have upgraded my s5 alternator to an FD alternator and wanted to make sure if about 19 volts is correct on Idle or is it possible that the regulator is not working properly.
Also 16 volts with headlights on.
I tested using the battery connections but at the moment cant find my new multimeter to be complete sure about my output

RotaryEvolution

iTrader: (30)

i think your voltmeter is broken, if it is putting out 19 volts then your battery is about ready to go chernobyl on your ***.

15 volts is high, 14.5 is high, 14 is kinda ok, 13.5 is about ideal under load, 19 is astronomical, i have never seen an alternator manage to put out that many volts even with a bad regulator and i don't even know that it is possible.

Trueno102

iTrader: (1)

Thanks, I thought it was high too gonna try it with a good multimeter, what's normal volts on a rd alternator?

RotaryEvolution

iTrader: (30)

13.5-14ish

TonyD89

iTrader: (10)

I had a battery go bad and it caused my alternator to overcharge. I found out because my stereo quit working, did have a voltmeter, and it was reading like 16 volts. I don't exactly remember as it was a long time ago. The radio quit working because it had a voltage protection circuit in it that wouldn't allow it to work. It had to be something like 11- 15.5 volts. I replaced the battery and it fixed everything. You should have heard that thing hissing and gassing, never had something like that happen with one before.

jetlude

iTrader: (9)

Yea, anything over 14V something not right.

jackhild59

iTrader: (7)

That is the full unregulated output voltage. Either your wiring is wrong, meaning the voltage sensing wire is not connected, OR the voltage regulator in the alternator is busted.

and yes, it will fry your battery.

Trueno102

iTrader: (1)

finally got a new multimeter and these are my readings
FD alternator
new battery cables installed
battery itself is = 12.5 volts
with car on by testing battery connection/ no accessories =14.40 volts

with car on by testing battery connection/ headlights,heater,stereo on= 13.75 volt at 1,000rpm
when i turn on the headlights, heater,stereo on the car slighty rises to 1,000 rpm on its own

but if I were to wait for a while the idle will go back to 800rpm and the voltage drops to =12.70 volts and it will continue to drop slowly, does this indicate too much load for the FD Alternator or is this normal


voltage drop test done as well

alternator output with positive lead (+) and
negative lead to positive battery post = -0.05 at 800rpm no accesories
with radio/headlights/heater on = -0.06 to -0.07 at 800rpm

battery ground with negative lead (-) to
alternator case with positive lead= -0.01 to -0.02 at 800rpm no accesories
with radio/headlights/heater on = -0.05 at 800rpm and -0.07 at 1500rpm

hope this is not too confusing

satch

iTrader: (1)

You might want to clean the grounding of the negative battery cable that is at the driver's side fender.

DaBrkddy

Are you running the correct size pulleys for that alternator? That idle voltage with accessories on sounds a bit low. If you are underdriving the alt that would probably explain it. I doubt you're going to over load the FD alternator with the basic factory accessories; it should still be able to charge at idle with accessories on.

Not to say you are underdriving your alt but feel I must say that nobody will ever justify for me the gains from underdriving the stock alternator on any street driven car. Any of the gains are immediately negated by the drawback of not having enough charge at idle/low rpm.

Trueno102

iTrader: (1)

Thanks for the comments guys

@DaBrkddy
I am running Japan2LA's fd pulley which i purchased on the forum but i dont have a pic
I also have the stock size belt on
I have checked all the main grounds aaroncake mentions on his page
Proper RX-7 Grounding Procedures

im going to check the driver side ground like @satch mentioned
also going to check the healdight grounds which i never checked

from what i understand is that its odd that it goes that low with the accessories i had on
maybe bad ground somewhere

ill give you guys an update

RotaryEvolution

iTrader: (30)

usually its the post off the alternator itself, theres another stud from there that goes into the alternator. if loose that connection gets burned and you lose voltage as it warms up.

Trueno102

iTrader: (1)

Got time today to clean all the grounds i thought might be giving me trouble.
I cleaned
1. shocked tower ground
2. rear brake light grounds
3. Rear Defroster ground
4. Front headlight relay ground
tested all these grounds with accessory load and all seem to be getting the correct output

no load voltage readings from these grounds
14.23 Alternator
14.06 battery post
14.06 rear left and rear right ground
14.04 defroster ground


readings with load at about 800rpm

headlights and defroster on only= Alternator reading is 13.82 volts and holds that voltage
headlights and stereo on only= Alternator reading is 13.80 volts and holds that voltage
headlights and blower motor on only= Alternator 12.80 volts and continues to slowly drop

It seems that my Blower Motor might be the problem. When i run the car on idle and have
the headlights, stereo, and defroster the voltage does not keep dropping but when i turn on the blower motor it will continue to drop voltage

Does anyone know where the blower motor ground is. Since the blower motor has high amp load i believe that might be a reason why the voltage keeps dropping.
Maybe cleaning that ground will help.
Maybe fan amp
maybe fan relay
not sure

Trueno102

iTrader: (1)

This is the only ground i found by the blower motor. This ground leads to the blower motor. I cleaned the ground. I would get 14.20 volts on this ground when blower is off.
This is the connector to the blower motor. I tested the voltage from this ground while it was connected to the blower. I would get 14.14 volts with motor off. Then i would get 13.30volts when i start the blower motor to high speed. Seems like a big drop and also continue to drop slowly again up to 13.18 volts.
There is a relay before it reaches the blower motor which I need to make sure works properly.
I need to check fan amp as well. I hear logicons do fails with the age of these cars. Bad solder joints could be a problem.

DankestKush

iTrader: (4)

Im currently trying to figure out my voltage problem. I have an s4 with s4 TII swap. S4 alt and S4 NA harness. i put a volt meter to the battery with the key set in the OFF position- 12.5V. When i start the vehicle my volt meter is showing in upwards of 22-24.5V. Alt then gets very hot, so then I shut it off. Voltage regulator perhaps? or maybe the wiring on the TEE shaped alt connector is bad? i remember reading about that somewhere.

barkz

iTrader: (1)

good lord change that alternator. That battery is going to explode