alternator wire

[mechtech]

labman - I think your are right - that is the real problem with his high powered music system.
An overdrive pulley for the alternator will fix this.
Many guys with mega watt systems do this.

 

[brianl703]

See if you can somehow make a 130amp Ford 3G alternator fit in there. Those put out 80 amps at idle!

 

[digitaldrifter91]

my stereosystem is not all that great, a few things but not alot, total draw counting the fuses is like 28 amps.

people have made a custom bracket to fit a 100 amp GM alternator but i dont have the resources for that.

i understand about "at idle" but what i dont get is even driving at like 2400 rpms it still is low when everything is turned on...

...and that the wire at the battery is reading at 14 volts where as the battery is not.

 

[brianl703]

One thing you could do is measure the voltage drop between the alternator output terminal and the battery + terminal.

Just start the engine, turn all the accessories and lights on, set your multimeter to DC volts, one probe on the alternator output terminal and the other at the battery. The displayed reading is your voltage drop.

It sounds like you have a voltage drop problem but this will confirm exactly how much it is. Then you can try to find the exact cause of the voltage drop--you might have a corroded or bad terminal or something.

 

[digitaldrifter91]

ok took ur advice.

at idle with everything running with loads and voltage at 12.16 is .698-.712 volts from positive battery to positive alternator.

from negitive battery to negitive at the alternator is .024 at 12.16 volts.

with everything off at idle from positive battery to positive alternator is .436 @ 14.12 volts.

so can you tell me whats up??

i looked at all my fusable links and they are good....im getting really stumped.

OH also one thing i found is that, if there is a load at idle, and the voltage is like 12.16 at the battery, its 12.80 at the alternator, and if i revv the motor the voltage at the alternator goes up to 13's but at the battery it only goes up to 12.6

so i dont understand.

 

[brianl703]

It sounds like you should upgrade the wire between the alternator and the battery (I am uncertain if you've already done this--if you have you probably shouldn't be seeing that much voltage drop), or check it for a bad connection somewhere.

Another possibility is that someone messed with the alternator wiring. Usually, there is a separate wire which runs from the voltage regulator to the battery (although it may not connect directly to the battery--on my Mustang it is connected to the starter relay, which in turn is connected to the battery).

The purpose of this wire is to allow the voltage regulator to measure the voltage at the battery, so it can compensate for voltage drop in the wire between the alternator and the battery by upping the voltage output from the alternator.

It's possible that someone reconnected this wire directly to the output of the alternator as a half-*** fix for a problem. This would cause the voltage regulator to measure the voltage at the alternator, which will not allow it to compensate for voltage drop.

You should probably get a wiring diagram and check this out.

 

[digitaldrifter91]

i did put a 8 guage power wire to the alternator to the battery but it made no difference at all in terms of voltage, i upgraded the ground from the alternator as well.

my voltage regulator is built in, but i was also wondering if that voltage regulator wire is somehow messed up and putting out not as many volts as it should.

i doubt someone half assed the alternator cuase we are the second owners and i think we are the one who put in both alternators, my uncle was the first owner but never swaped alternators.

haha im super scratching my head!!

 

[Gary Allan]

digit...if you're seeing less VDC anywhere then you do at the lug on the alt ..you HAVE to have a V-drop across that wire between them ...no two ways about it.

For example, you can have two wires connected to two batteries and only joined at the lug of the alt ..and you can suck one battery dry (let's say it's hooked ONLY to your amp) and the other will never dip in VDC as long as the lug is still at above the level of the other battery. There has to be a differential to enable current flow. So while the battery will "dump" current into the demand that you're putting on it ..the Alt lug is limited to whatever current ceiling it has with 14.X pressure. When you elevate the demand load above that output ..the wire becomes part of the resistance equation.

Just like you can't power your fog lights with the low current relay prong if you hook up the relay wrong. There's 12VDC at the prong ....hook up the lights ...NO WORKIE. A dead short across it only delivers .00001ma of current (a number I pulled out of my arse).

This is why many who "self engineer" dual battery systems end up wearing out one battery before the other to a very large spread. One battery will do all the work ..and the other will sit there and do nothing. Oh, it will "balance out" somewhat ..but the lions share of the current will be dumped by one battery ...just due to the cables between them presenting different resistance. That is, one battery "sees" a great demand ..and the other sees what's lacking.

[ May 29, 2006, 09:04 AM: Message edited by: Gary Allan ]

 

[kc8adu]

did you crimp or solder that 8ga replacement?
unless you have a high quality(expe$en$ive)crimp tool made for the type of terminal you are using you are not likely to make a good connection.
the high resistance in the crimp will soon show up as it overheats and eventually fails by burning up.
i crimp then solder.i just got an electric"cripple car"scooter very cheap.it would not pull hills and the battery gauge would drop into the red even with a known good battery set.all the crimp connectors were discolored and the mfr used an iec power cord to the battery box!stupid in the extreeme!
wonder how many accidents/injuies happened when folks thought they could charge with a pc power cord.
anyway check those terminals for bad/high resistance connections and report your findings.bet thats your problem.

 

[digitaldrifter91]

thanks for the info guys. now do you think that the 8 guage power wire is just not enough for my alternater and i have to run a 4 guage wire from the alternator to the battery?

...i only used a crimp connector but crimped it really good, yet maybe not good enough. is there other things i should be looking at near the battery? terminals seem good though im looking into putting other types (aftermarket) on there at the moment.

 

[04SpecV]

#8 should be plenty for those distances. But 4 would not hurt.
According to the measurements you posted by measuring across the Positive wire it seems ok.

Did you measure from the Negative battery post to the alternator case?

Are you sure the alternator is good? The voltage seems very low.

 

[digitaldrifter91]

from negitive battery to negitive at the alternator is .024 at 12.16 volts

the atlernator is good when everything but one thing is on

 

[Gary Allan]

So, you're ONLY getting 12.184VDC at the atternator lug

That cannot be right.

Wait a minute. I forget what year this thing is. Normally, a stand alone alternator would just have Zener diodes regulate the voltage. Now the PCM may control the alt output by cycling the field ground. This can be altered by the battery temp sensor, if so equipped. Otherwise you should be seeing about 2VDC drop across the lug to the battery to read 12.xVDC there.

Are you sure that you're reading the right 'range'? 2.4VDC would be what I expect.

 

[digitaldrifter91]

nah, i am getting 12.18 at the battery and near 13 at the alternator.

this is a 86 nissan 300zx non turbo. it has a 70 amp alternator but i put a 90 amp alternator from a maxima.