fcdin

iTrader: (1)

To start off. I had two alternators that went out on me. Third one I got from autozone. Now what I'm wondering is that. Could they have given me the wrong alternator?! I mean, when I went to go get a stereo harness for my 89 gxl at a car shop (also at Best Buy). They came out with a harness that didnt fit mine. It was a S4 harness. Now I was reading about how the 2 different alternators are wired differently. Could that be what's going wrong with my car?

mort2002

iTrader: (1)

IIRC the plugs are differnt from S4 to S5. so you couldnt have mixed them up...

Digi7ech

iTrader: (1)

Different voltage output and schematic.

S4 has 2 plugs on the back while S5 has a 2 pin plug on the side which also needs a constant 12v source or it'll drain your battery.

Search for FD alt swap and you'll find a picture with all 3 alternators on there and how to wire them.

mort2002

iTrader: (1)

ive noticed taht when my car runs at idle my voltage is low but when i start going ti jumps up. at idle ill see like 12.5v and driving i get like 13.8... wonder if my alt is going bad...hmmm

fcdin

iTrader: (1)

Mines almost the opposite. When I start it. It reads 14. Then when I start driving it drops down slowly and then dies. lol..

mort2002

iTrader: (1)

if i have my head lights on and my rear defroster my voltage is way low like 12.2....

Digi7ech

iTrader: (1)

^i get the low voltage at idle as well. Do you have a dual pulley on?
If so, I bet it's not the sam esize as the stock one which woudl make me think it's underdriving it a bit at lower rpm's.

mort2002

iTrader: (1)

actually i have the stock pully on still.. i knwo its a no no but i havet bought the dual yet..


OH YEA MY POST #600 w00t w00t

JayDMfanatic

so is there a diffrence in the wire haness from s4 to s5? so an s5 inake manifold with sensors wont plug and play with n s4 engine harness? its diffrent?

Digi7ech

iTrader: (1)

electronics between s4 and S5 are very different.

Back on topic.
adding an additional power wire from the main fuse block to the B post on the alternator may help kick up initial voltage if the stock wires are getting old and cranky.

bradenscreed

what about those voltage "caps" people use for their stereos? would one of those help out?

Icemark

Auto zone alternators are typically very questionable as they are usually are just rebuilt alternators. I can not ever recommend Autozone alts.

Rebuilt alternators only have the part that is bad fixed, then they clean them and sell them. The almost always do not have all the parts needed to be replaced, actually replaced, but just enough to pass a bench test.

The S4 alternator could not be swapped with a S5 without changing plugs and wiring (although the comments about needing battery voltage for the refernece is wrong- but because too many people don't understand alt wiring I am not going to go into it right now).

A cap (or more correct, a Capacitor) is used to provide surge voltage in high demand situation. It is really just a band aid for a weak supply system, and will not come close to solving the problem unless your problem is being caused by too big of an amplifier for your sound system (and even then, it doesn't solve the problem, it just masks the voltage to the amp.

And once again, proper voltage with the engine running is 14.4 volts. If you are less or more than that, there is a problem.

fcdin

iTrader: (1)

When I started the car. It went great. It was around 14 or so. Then I let it sit to warm up and it slowly drops to 8-10 volts. Warning lights arent all on to tell me that the alternator is not working. Connection somewhere maybe?! The alternator I got from the junkyard was giving me 16 volts and that one went out on me too. Could that have fried my cpu and/or other wires?! I do have two 12 inch kickers in the back with no amp, but it worked out fine when I had the original alternator in (that was about for three months). Also got a new battery about a week ago.

Digi7ech

iTrader: (1)

Are you referring to my post about the S5 needing a 12v constant like the FD alt?
I said that because of this


Correct me if I'm wrong.

Icemark

I know that drawing, and yes it is correct for the S6. But the S5 alt can be wired to the ignition and not have battery draw issues if the installer didn't mix up the two wires and blow out the diode in the alt when hooking it up.

But since the vast majority of people working on their 7's don't meter their wires before hooking anything up, and just guess... well then that drawing just just perfect for them.

My5ABaby

iTrader: (7)

So the S5 "S" terminal can be wired to the ignition? If so, what's the advantages to doing so? And... by mix up the wires you mean (S5) "L" terminal to ignition instead of "S"?