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-   -   91 FC Voltage? (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/91-fc-voltage-710732/)

Mushiki 12-06-07 02:43 AM

91 FC Voltage?
 
I have a 91 FC, it's the weird NZ/Middle East spec one --

I was just reading the FC FAQ, and noticed this:



The voltage in my car is Low or High
Normal operating voltage for cars is 14.4 volts. This is where the voltage should be when the engine is running. If it is not at this voltage, there is something wrong with the alternator or charging system or wiring.

13.5 volts is the bare minimum to charge the battery. Anything less than 13.5 volts while the engine is running is bad and indicates that the alternator is failing or mis-wired.

12.6 volts is battery voltage. If the car is at 12.6 volts or lower while the engine is running, then the charging system is not sufficent to even keep the car running and the car is running on the battery. This indicates that the alt has failed, or is disconnected.
I also noticed that my car's voltage reads the following:

http://i26.photobucket.com/albums/c1...i/DSC02562.jpg

Does this mean that there's something wrong with my alternator or something? :(

cmanns 12-06-07 02:46 AM

Mine runs fine, when I turn the key to acc (or w/e makes cluster lights go on) its about the line above the 8, when i turn her over it goes slightly lower, then once she starts and idles at 3k rpm its about before the line above the 12.

When its idle/lights and brakes it is at where yours is, I have no problems occasional stalling (Auto tranny is fucking up now) so I'd say your fine\ aslong as it goes up when you rev it past 1k rpm a new alternator and battery wouldn't hurt though ;)

ivegonemad 12-06-07 02:47 AM

you didnt clarify if your engine is running in the pic?? your alternator might be going bad....or is starting to fail...as it stated....

cmanns 12-06-07 02:47 AM

His engine is on man, look at the oil pressure gauge.

ivegonemad 12-06-07 02:49 AM

i did not even see that...lol...

cmanns 12-06-07 02:50 AM

Go to bed x]

ivegonemad 12-06-07 02:51 AM

best advice ive gotten today...

getbent69 12-06-07 04:51 AM

Run a multimeter on the battery to confirm the reading you getting on the dash is accurate.

Mushiki 12-06-07 09:49 AM


Originally Posted by cmanns (Post 7591761)
Mine runs fine, when I turn the key to acc (or w/e makes cluster lights go on) its about the line above the 8, when i turn her over it goes slightly lower, then once she starts and idles at 3k rpm its about before the line above the 12.

When its idle/lights and brakes it is at where yours is, I have no problems occasional stalling (Auto tranny is fucking up now) so I'd say your fine\ aslong as it goes up when you rev it past 1k rpm a new alternator and battery wouldn't hurt though ;)

Thanks for your advice.

My battery is basically new though.

So I guess the alternator is going bad.

siguy2k 12-06-07 03:27 PM

Thats down where mine was getting before I parked it for the winter. Mine was so bad that when id push the brakes it would shut my radio off for a sec. I would like to know if there is some sort of high output alternator for the FC? I believe if you have a s5 the FD alternator will drop in with a pulley change, but not 100% sure.

classicauto 12-06-07 04:22 PM


Originally Posted by siguy2k (Post 7593667)
Thats down where mine was getting before I parked it for the winter. Mine was so bad that when id push the brakes it would shut my radio off for a sec. I would like to know if there is some sort of high output alternator for the FC? I believe if you have a s5 the FD alternator will drop in with a pulley change, but not 100% sure.

Yep the FD alt will work perfectly with a pulley change.

The S4 guys need to do a little wiring, but S5 guys can simply just swap the plug (or wire the alt directly) and utilize the FD alt's additional amperage.

To the OP - I would second the "check the battery wil a multimeter" notion. If you're getting 14ish volts at the terminals, all is well. Anything approaching 12.5 is bad, means you're running on pure battery power.

cmanns 12-06-07 07:55 PM

When you turn on the lights does it just dim alil bit and when you apply the brakes alil more?

I don't think I'm running on battery lol, once I turn off the car after driving it around the needle does go up a mark but its whenever the cars idle when the dash is slightly more dim, when I rev it up the lights get brighter just a TAD like you'd have to be crazy to notice it.

My dad did have the alternator rebuilt before giving it to me since the battery was always dying, but the battery was actually 8-9 years old, replaced it and the cars started fine since.

Then again my battery is really cheap and looks small and dinky, would that make a difference?

ericgrau 12-06-07 08:33 PM

mushiki: Verify the numbers with a multimeter on your battery while the car is running. If they are correct, your alternator is totally gone. It's time for a new one. Ask a mechanic for a good alternator shop, or if you can't find one then make sure you save your warranty info. Alternators are a gamble; you might get a good one first time or you might get multiple alternators that last only a couple hundred/thousand miles. If so just keep replacing them or find a better shop.

cmanns: Your alternator is going, but it is still putting out some juice. You can get a jump box at Walmart for about $40 if you want.

In both cases it might also be the battery (but probably not). Most auto stores will test your alternator and battery for free, and they're both easy to remove. So you might as well test both. You will need wrenches for the bolts, maybe a mallet to get the alternator loose, maybe a hammer to force the spacer back in when you reinstall, and some kind of prying bar to pry on the alternator while you re-tighten the belt afterwards. The center of the long section of belt should give about 1/4"-1/2" (6mm-12mm) when you push on it with your finger. Battery is just bolt-off, bolt-on.

cmanns 12-06-07 08:40 PM

One of my belts is too long, just alittle the thing that you tighten those parts to to make alil tension ont he belts is maxed out, I can't recall if its the alternator or the power steering (My dad was just bla blaing about stuff)

Would that cause it? He said the alternator was fine, I told him it wasnt but I don't know when he changed the belts (Was a long time ago) he wants to change them before he leaves this month but I didn't think the longer belt was a problem, if its longer as far as I can see it'll cause it to turn slower, if I rev to to 1k the lights brighten and the voltage gauge goes up slowly, but I don't know...

clokker 12-07-07 07:15 AM


Originally Posted by cmanns (Post 7594928)
I didn't think the longer belt was a problem, if its longer as far as I can see it'll cause it to turn slower

It's the pulley diameter, not the belt length, that governs the RPM of the alt.
A longer belt would just necessitate cocking the alt up higher on the adjustment arm.

If the belt is so long that the tension cannot be adjusted properly, it could be slipping but in that case you'd probably hear the belt screaming and may even overheat some as the the waterpump would be affected as well.

Mushiki 12-07-07 03:05 PM


Originally Posted by cmanns (Post 7594775)
When you turn on the lights does it just dim alil bit and when you apply the brakes alil more?

Lights dim whatever I do...

I press on the brakes, everything dims, even the revs go down a tad... I change the AAS setting... lights dim... I turn the AC on... lights dim, revs go down, power-steering feels heavier... I also noticed that I get the clasic 3800rpm hesitation, most likely beause they secondary injectores aren't firing (I believe it's related to this electrical problem as well).

Now even the power windows are giving me a hard time when I try to pull them up...

Also, when I am driving around, and I brake and come to a full stop, I can see the voltage (via de volt gauge) dropping to about 8v for a second.



Originally Posted by ericgrau (Post 7594908)
mushiki: Verify the numbers with a multimeter on your battery while the car is running. If they are correct, your alternator is totally gone. It's time for a new one. Ask a mechanic for a good alternator shop, or if you can't find one then make sure you save your warranty info. Alternators are a gamble; you might get a good one first time or you might get multiple alternators that last only a couple hundred/thousand miles. If so just keep replacing them or find a better shop.

Will do!

cmanns 12-07-07 03:59 PM


Originally Posted by clokker (Post 7596211)
It's the pulley diameter, not the belt length, that governs the RPM of the alt.
A longer belt would just necessitate cocking the alt up higher on the adjustment arm.

If the belt is so long that the tension cannot be adjusted properly, it could be slipping but in that case you'd probably hear the belt screaming and may even overheat some as the the waterpump would be affected as well.

I hear a belt scream but yeah I don't think its causing the alt to not run quick enough, guess its bad :icon_no2:

As to the OP, yeah man your alt is going if the rpms drop then I'd also say you have a bad battery too it did that when i had a completely dead batt it'd go down a bit whenever something was turned on.

Mushiki 12-10-07 05:39 PM

Just checked, and my multimeter reads 13.35 volts...

This means my alternator is dead or about to die, right?

Icemark 12-11-07 09:19 PM


Originally Posted by Mushiki (Post 7608674)
Just checked, and my multimeter reads 13.35 volts...

This means my alternator is dead or about to die, right?

Yes, either that or that you have a huge drain on your electrical system from some aftermarket amp or other aftermarket electronics.

And your bump has been deleted. Bumps are forbidden here in the 2nd gen technical section.



.

ohayou88 12-11-07 09:56 PM

what about with the headlights on. I assume that when u turn on the headlights and fogs and stereo the voltage is suppose to drop? or is it suppose to remain the same at all times?

SpeedOfLife 12-11-07 09:58 PM


Originally Posted by Icemark (Post 7613878)
Yes, either that or that you have a huge drain on your electrical system from some aftermarket amp or other aftermarket electronics.

And your bump has been deleted. Bumps are forbidden here in the 2nd gen technical section.



.

I've been seeing about 13.8V at idle and around 14-14.1V at 3k-5k RPM, is that reasonable or could it be caused by my bad ignition switch? (I'm pretty sure my ignition switch is a piece of crap, I'm replacing it in a few days when the new one arrives)

Icemark 12-11-07 10:41 PM


Originally Posted by ohayou88 (Post 7614027)
what about with the headlights on. I assume that when u turn on the headlights and fogs and stereo the voltage is suppose to drop? or is it suppose to remain the same at all times?

If the alternator is in good condition, it won't matter... there should be no drop with stock electronics.

Now if you have hacked in some aftermarket electronics or electric fan, then the stock alt will be undersized... but for a basically stock system there should not be a drop.

Icemark 12-11-07 10:42 PM


Originally Posted by SpeedOfLife (Post 7614037)
I've been seeing about 13.8V at idle and around 14-14.1V at 3k-5k RPM, is that reasonable or could it be caused by my bad ignition switch? (I'm pretty sure my ignition switch is a piece of crap, I'm replacing it in a few days when the new one arrives)

ignition switch will have nothing to do with the alternators output unless you have a non stock alt, that is not wired correctly.

Mushiki 12-12-07 09:13 AM


Originally Posted by Icemark (Post 7613878)
Yes, either that or that you have a huge drain on your electrical system from some aftermarket amp or other aftermarket electronics.

My car is completely stock, the only aftermarket electronic I have installed is a Sony MEX-1GP CD player.

Icemark 12-12-07 03:27 PM


Originally Posted by Mushiki (Post 7615466)
My car is completely stock, the only aftermarket electronic I have installed is a Sony MEX-1GP CD player.

Should be fine then... your alt is probably just old.

Unless it is dropping or staying under 13.5 voltson a regular basis then I wouldn't worry, as you probably have a little life still in it.

On the other hand, now would be the perfect time to rebuild the alt... before anything fails miserable and strands you.


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