I'm sure this has been asked before, but the search function isn't working for me. I have an '88 non-turbo, and after having low voltage trouble with 3 rebuilt Mazda alternators, I am wondering if an S5 alternator (with 80amps instead of the 70 in an S4) is a direct plug-and-play for an S4 car. By that I mean, will it plug in directly with no modification.
Thanks!

 

idon't think that it will be a direct swap. you should just go with the fd alt. i don't know where to get one cause higgi quit selling them but i know he sales the pullies though. also have you tested to see if you had a short in the wires and also do you have a stereo system?

 

Nothing was changed except the alternator since the original gave out at 170000km.
So is the final word that they are not a direct swap?

 

no. but i think that it is just minor modifications. also if you could get the plug for the s5 alt then all you would have to do is just cut the harness and then solder the new wires together.

 

Not interested in performing modifications. Mazda is ordering a new rebuilt alternator tomorrow morning, and I'm supposed to let the parts guy know by then if I want to go for the S5 alternator instead. If it's not a direct swap, forget it.
Thanks for the info.

 

Should be a direct plug in since the S5 alt sitting in my garage looks exactly the same as my S4.

BTW why go through Mazda? You like to over pay?

Go to Checker and get one with a lifetime warranty.

 

Yes, I like to overpay. I bought a rebuilt one back in September, and it's covered by 1 year warranty, so until that year is up I will be dealing with Mazda, since it now costs me nothing. I have a good relationship with the local Mazda dealer; their prices are decent, and the service is excellent.
I guess I'm mainly trying to find out if the electrical socket on the S5 alternator will fit the S4 plug, and if the alternator will mount properly in the S4 bracket.

 

The plug is the same but I don't know about the bracket point. I assume it's the same since I have a mixed S4/S5 engine and the S4 goes on fine.

 

Thanks. I'll give it a try.

 

My S5 altenator had a bigger plug then my s4. I dont think they are the same.

 

plugs are different between series, but the S5 alt does bolt in.

 

^MISINFORMATION...Try again.

The S4 and S5 alternators are physically the same and they have the same pulley. There are however two differences that need to be addressed. First, the plug that connects to the back of the alternator is different. Second, the S4 alternator has an internal relay that disconnects the internal diodes from the battery when the engine is shut off. The S5 alternator does not have this internal feature. So you must install an external relay so that your battery does not go dead. If you don't install the relay, the battery will slowly go dead in approximately 5-7 days.

 

hmm didn't know that. The plugs looked the same to me. Good thing I dodn't sodler the S5 plug on there then from the Jspec.

 

Could you give more info on this ?? please.

Looking at the s4 alt diagram in FSM, it seems that the only way the battery could get drained when ignition is off is through the bank of 'output diodes', so unless they are leaking, I doubt current can go through.

Note that path to ground from terminal L and R are cut off when ignition is off.

There is no sign of a relay on that diagram on the path from terminal B to ground going through the output diodes, but that does not mean, there is not one.

so if you could elaborate, that would be great.

thanks,
Hugues -

 

Whoops PARTIAL MISINFORMATION... try again...

The relay myth was created by bozos that didn't know how to wire the alternator correctly and had the run and refereance leads of the alt backwards.

Indeed if the run and referance leads are reversed, the battery will drain is about a week (and often the protection diode internal on the alt also smokes).

But wired correctly you will never ever need a relay, as there is not one on the series 5 alterntors or even the FD alts.

This has been covered in great depth on teamFc3s.org in the turbo section as well as posted here several times.

So for both Digi7ech and wozzoom please do not post what you don't know and are guessing on. it only screws people up, or makes them believe dumb things like an alternator having a relay.

Here's a picture of the S5 alt internals as well as wiring...

The run lead is the white/black (W/B), while the referance lead is white/blue (W/L). The black/white is ofcourse the feed to the fuse box/battery.

Of course you can clearly also see the difference in the plugs for the S5 alt. Note that the FD alt uses the same plug as the S5 non turbo alt.

Now here is the S4 alt (and starting/charging system) (and plug!)


You can clearly see that the alt is near identical internally... infact if anything has a relay it is the CPU! Of course this same run feature is found moved into the Clock/warning panel on the S5 cars since there was no longer room for a alternator run relay in the CPU.

Now, what really confuses people... is that Mazda switched wire colors for the S5 car over the S4... so that is why so many shade tree mechanics mix up wiring of a FD or S5 alt into a S4 alt. Note how the White/Black is still the same, but the referance lead is black/white on the S4, while it is White/blue on the S5...

So where does the battery drain come from that wozzoom was talking about???

It comes from if you mixed up the (S4 colors now) Black/white and White/black wires. This allows the 12volt feed from the battery to always feed back into the alt (regardless of what series alt the car is using). This then would power the regulator circuit in the alt and drain your battery. Of course this also backfeeds the alt warning relay in the CPU... and if toomuch current is run, smokes the referance diode. Again the typical shade tree mechanic, will figure, "White/black... hmmm that should go where the white/blue is... right???"

WRONG.

So you can see that there is no relay needed (in fact there is already a relay on the S4 car- so there is really no need for a relay). This same info works for the FD alt installed into the FC as well.

 

He was feeding you bogus info... the only way the alt can drain the battery is if the run lead and referance lead are mixed up (of course that tends to blow the alts internal referance diode (the white/blue wire's feed on the S5 alts, and the Black/white wire's feed on the S4 cars).

 

Well there you go! For some reason I knew Icemark would set me strait... Thanks for the schooling. My elec. engineering skills (lack of) bow to your superior knowledge.

*STICKY PLEASE!*

 

If you take off the small two wire connector on the alternator...and with a meter, see 12v on the blade in the alternator that feeds the idiot light relay in the CPU....that would mean a diode is busted in the alternator.

But all you would have to do to remedy that is to buy a diode like a 1N914 from RadioShack for a buck or so...and splice it in the small black/white wire that connects to the alternator. Then no more backfeeding. Back to normal.

 

Hey this is kind of on topic. I disconnected the plug behind my alt since it was backfeeding my EFI and kept the car running. SO far I have run the car with the plug disconnected and no idiot lights went off. Any idea why?

I thought they would go off if the car was running and it didn't detect the back plug?

 

On a series four, the alternator puts a ground on the white/black wire when the alternator is not putting out. That ground is put on a relay in the CPU. When the relay pulls in, the contacts on the relay close and send 12v to the idiot light cluster and turns the idiot lights on. When the engine starts and the alternator puts out, the ground is taken off the white/black wire and the relay in the CPU closes and the idjut lights go out.

If you have a series five alt in a series four, the black/white wire goes to your left if your looking at the alt from the front. And the white/black wire goes......yes.

If you have a series four alt in a series four car, and the idiot lights don't go out or the car keeps running, the plug must be broken and you have had the two wires in the wrong places. My best guess.

By the way, I ran one of my cars with the small two wire plug off for months without knowing it. I just thought the idiot light cluster was bad. Oh well.

On a series four alt, the black/white wire goes ABOVE the white/black wire.....just like the pictures above.

 

hmm odd.

The whole guage works on my S4 NA cluster in my conversion.

The idiot cluster didn't light up though. Then again it never did when my alt actually crapped out. I found out it wasn't working by the stereo and battery dying while driving.

I'm going to cut and reverse those wires soon and I'll plug it back in and see if it still backfeeds the EFI or not. If so then I might have wirednit wrong. Everythig works fine with it out though.

 

You got a 88 model that was a non turbo.......and you put a turbo engine in it.......so the question is.....what alternator is in that car right now....and do you have the original harnesses in the car .......and if it's the original harness.....did the plug get screwed up and you at some time just took a fifty fifty chance and put the two wires on the alternator?????

And if you go out to your car, and turn the key to OFF, and put your mieter neg on the battery and the positive lead on either of the blades that are a part of the jack on the alternator, does either blade show battery voltage?????

And you know on a series four car the black/white goes above the white/black. And that by some chance you have a series five alternator in the car...that the black/white wire goes to your left as you stand in front of the alternator and the white/black goes to the right and that the above is true IF you still have your stock series four harness in the car.........but is not true if you have a series five harness in the car ?

And why did the Iceman try to fool us into looking at this post by making another thread? Mystery there.

 

OK well it's a Series 4 Turbo EFI harness. Also a S4 Alternator I took off my S4 NA before it blew the engine.

When I did the wiring I toned out the alternator plug on the NA S4 harness. Those pin outs on the TII harness were just Y'd into other lines line ground and power or something. So I cut those and closed off the extra Y line and ran 2 new wires up to the Alt.

Since the car constantly ran with it plugged in I assume I reversed those wires.

------------------------
The test you mentioned above.
So I should hook up to a ground (Does it have to be neg term or any ground will do?) Then I need to check for voltage from either of the pins when the car is in off position(keys on in right?)

Now if it does have voltage it's a bad alt???thx.

Should I test the plug wires for voltage as well just in case?

 

Nothing on a alternator should be grounded.

Take your keys....and place them in the backyard, then go to the car.

Assuming that you have a meter.....put its negative lead on the battery ground ..oh heck any ground will do. Then take the positive lead and touch it to one of the blades in the alternator jack...then the other. The meter should be on DC volts. There should not be any voltage reading.

Now go out to the backyard and get your keys. Put the key to ON. Now go to those two wires that should go to the alternator. The black/white wire should have 12v on it....but to tell you the truth the white/black will have voltage also, but it will be a touch lower. As much as a volt lower.

Anyway, connect the black/white to the upper blade on the alternator and the white/black to the lower.

Start the car. The alternator should work and you should see 13 something volts. Turn the key to OFF. The car should stop running. IT WILL stop running.

If when you touched the alternator blades one at a time....and one or the other had battery voltage.....I think there is a diode busted. That can be overcome by putting a cheap buck fifty diode in the wire that connects to that blade.

Nah, never ground squat on a alternator. Ain't no need. Don't need to ground ignitor assy's either since they're bolted to the darn chassis. And you don't need to ground..........

 

OK well I tested it.

It had no voltage on one of the prongs and had like .001 on the other.

I then put the key in and tested the 2 wires.
They had similar voltage of around 12.
Key out they had nothing.

My battery voltage is pretty low but I'm guessing it's due to an old one which sat for 6 months. I have also tested voltage of the car running with the plugs out of the back and it was showing 11.9 so I'm guessing the Alt is fried anyways.

I have a newer one sitting in my parts car so I'll swap that in soon.