Hi everyone,

My car's a S4 FC, 67k miles, completely stock -- just a cone air filter installed.

Car runs perfect, idles solid at 750~800rpm, has no problem whatsoever except from aux ports that seem to get a bit stuck at times, and some bucking on decel.

Just performed a 60k tune-up... new oil filter, fuel filter, sparkplugs, ignition cables, thermostat, rad cap and belts.

Seems like I am having an electrical problem of some sort... my in-dash volt-meter reads like this when the car is running, with no electrical accesories on:



-- and idles perfectly:



The volt-meter I assume is lower than it should... I check with a multi-meter at the battery, with the engine running, and I get about 13.4volts

I have no problems when starting the car, starts right away.

Noooow... when I have the lights on (8000K Xenon), front wipers on, and the fans set to max (without the AC on, just the fan)... the in-dash volt-meter reads this:



-- and my idle goes down, and gets a little bit unstable:



To make maters worse, the moment I hit the brakes, the "Antilock" ABS light goes on in the idiot cluster...

Is this... normal? I don't like it at all... I mean, if this is what happens without the AC on, I cannot imagine how shitty things can be with the AC running...

What should I check? Maybe the alternator is about to die? Maybe the battery is on it's way out?

Help!

 

any thing under 12.5 volts and that means your alternator is not working or failing.

 

I'm getting 13.4v at the battery, with the engine running -- should I check somewhere else?

 

What makes you think that when the gauges show 4 volts less than that?

 

I don't know really

Just felt like asking, since several people told me not to trust the gauge much...

I assume my alternator is on it's way out then...

 

What do you get if you put the digital meters positive lead on the large B output terminal of the alternator and the meters negative meter lead held agains the alternators body? Idling. Write back. Should be 14vdc plus. Higher if the alternator is cold/cool. As mentioned, at least idling, but see what it is when the revs are at 2000 rpm.

I don't know why your gauge would read that much off the digital meter at the battery posts. Like I say, try the alternator output wire as described above.

 

With the B terminal disconnected?

 

Oh no. All plugs terminals on the alternator. You want to check the voltage output AT the alternator itself. Then comare that reading with the reading across the battery terminals. The voltage should be over 14vdc with the engine running. Might rev to 2 grand to confirm that.

I was just curious if there is a major voltage drop from the alternator output to the battery/engine bay fuse box.

Never run the alternator with the terminals not connected. Same with removing a batt terminal with the engine running.

If memory serves......the alternator puts out.......voltage goes from the alternator to the ignition key.........turn the key ON and the voltage goes from the key to feed IG1 and IG2 fuses in the engine bay fuse box..........the METER fuse is on one of those two busses and the METER fuse feeds the gauges/voltmeter in the gauges.

Or like the jpg out of the FSM, the power comes off the connector FE-01 at the top of the page..........goes to the ignition switch where they show (B).........turn the key ON and it leaves the ignition switch on the wire I colored in RED.....................to feed the fuses in the block off fuses named IG1.

Then, not shown, it leaves the METER fuse in IG1 and goes to feed the voltage gauge in the cluster. Why you have such a voltage drop from the alt to the cluster gauge is unknown to me.

 

I just checked, idling, with the engine hot, the alternator is puting out 13.4vdc

Also measured at the battery, 13.25vdc

I'm a retard, and forgot to check at 2000rpm...

 

Well rev it to two grand and see what it says. I really can't explain why the gauge shows so low. I'd expect maybe a half volt lower than the alternator output but not what your seeing.

When idling, have you looked at your WARNING light cluster to see if the CHARGE light is dimley lit?

 

I'll check again later today.

What worries me isn't what the gauge is showing... what worries me is that my car simply doesn't like having many electrical accesories on at the same time... I mean, my ABS light goes on with just a couple of things on, and not even the AC working...

 

Pull the gauge cluster, clean off the screws that hold the voltmeter in place on the back of the cluster and then add a little conductive grease to the tip if the screw and the washer on the screw. Then tighten the screws back into place.

You may have either a loose or corroded screw connection if the voltage is really 13.4 at the battery and the alt.

But even 13.4 is pretty low and only barely able to charge the battery. Too charge the battery correctly you need at least one volt more than the battery (or 13.6 volts).

 

Checked again yesterday, this is whay I got:

Idle
- 13.6v at the Alternator
- 13.45v at the Battery

2000rpm
- 14.2v at the Alternator
- 14.05v at the Battery

The dash gauge showed about 12v at 2000rpm, and slightly lower than 12v at idle.

Then again, I don't care much about the dash giving me a proper reading -- I am worried about not being able to use the AC or other accesories without ABS giving up on me ad stuff...

 

Go to the ABS control unit and pull its plug off and also the plug off the hydraulic unit.

Idle the engine.

Check the voltage at the B/Y input wire of the two units. If it's not the same as the battery voltage at idle (you say 13.5vdc approx) but looks more like the measley voltage at the volt gauge in the cluster, then you have a power feed problem.

The power flow is as described below:

Power goes from the alternator..............thru the key if ON.............to the interior fuse box to feed IG1 and IG2...............leaves the fuse box thru the fuses on those busses to the items the fuses are for.

Just in case: IG1 and IG2 are buss bars with fuses attached to them. The METER fuse that feeds the volt gauge is on IG1 and the ABS is on IG2 as shown in the dwg attached. We already know that IG1 is low feed to the guage, and I bet when you look at the B/Y wires at the hydraulic unit and ABS control unit they are also low.

Maybe check the fuses in interior fuse box at idle to see what the voltage is there. Check at the fuse I point to with the BLUE arrow.

It would be worth looking at the volt gauge after you have removed the plugs from the ABS units and see if it goes up or not.

Then again, I wonder if there is some aftermarket bs wired into the interior fuse box causing this problem. Got any aftermarket bs attached to the stock wiring?

 

Thanks for your time and help Hailers

I'll check voltage later today, with and without the ABS unit plugged.

Regarding aftermarket bs... the car has an aftermarket alarm system, which I didn't install myself, it was professionally done... so I wouldn't know.

What scares me here is the fact that I feel like the car is about to stall every time I hit on the brakes, with just a couple of accesories on (lights, front wipers, interior fans...) -- I can imagine it would stall immediatelly if I turned the AC on... or the rear defroster.

 

bump deleted... no bumps allowed here Mushiki.

And the low voltage on extra accessories on probably means either it really isn't low voltage (Hailers test will show you if this is the case) and you have corroded screws at the back of the cluster, or your BAC is bad, or your alt is bad (which we already kinda know since it is not putting out 14.4 volts at idle with nothing on).

 

Might be a bad ground. Check all your grounds. Start at the battery first. Follow the negative battery to the chassis ground. There's another ground underneath the trailing coils. Another behind the motor bolted to the top of the transmission. That ground is connected right next to windshield wiper motor. There's a write up on better grounding in the archive section.

 

Worked on some of the grounds... the main ground, one that's close to the main fuse... the one that goes from the tranny to the firewall... the one on the starter...

The one I didn't check is the one that's right on the engine, you know, close to the solenoid rack.

Stll... nothing changed.

I did notice something strange today... I was checking the manual for the NA S4, and noticed that the alternator is different to the one I have... I checked my alternator again, and it seems to be one of those N350 S5 80A alternators...

The thing is, that alternator is running on a belt for a S4 alternator... could this be the cause of all my problems?

 

nope not the problem. im running S5 alt with s4 belt

 

Yep, the two wires are reversed on the S5 alts over what the S4 alts use, but if you have blown the interior diode, the the alt will need to be wired to a 12v+ source like the battery.

The FAQ for FC sticky thread and 2nd gen archive both have a diagram on how to wire a S5 or S6 alt into a S4 car.

 

Well... my car came with this alternator from the factory...

It's a version sold in some regions... like the Middle East or New Zealand

S5 body, S4 engine, S3 ignition system, a unique ECU... and well, seems like it also has a S5 alternator.