eddie jr

ok, it's an 85 2.8 V6. I was working on the engine and the treble light slid down the side of the alternator and touched the red output terminal (sticking out far beyond that retarded plastic guard )....spark....then low guage when driving. I have heard neaver to ground that terminal or the alternator can fry....True???

Oddly enough, the alternator tested fine (Bench test only, not in the car) today but I am not confident with that test because it has proven wrong before on another car, twice.

So my question is, is there any fusible links in the alternator circuit that could have blown? I don't see any in my wiring diagram. What about that 10 kohm resistor in the guage line (i have the guage not the light)? The red terminal reads battery voltage wit4h the car off so power is getting there and to the red wire spliced to the harness. THe only other one is the brown one to the guage.

Are there any fusible links etc? Any suggestions?

thanks.

Maverick H1L

iTrader: (8)

Oddly enough, you can fix this yourself. You (if in fact the alt has been toasted) can go out and get a diode and rectifier set and fix it for a lot cheaper than trading it in for an unreliable supposedly rebuilt unit and a whole bunch cheaper than a new one.

There's only one way to know if the alt has been toasted-if the batt starts dying within a week of the car sitting doing nothing or if you are driving down the road and the voltage drops...

You can do a multimeter test on the alt but you will need a service manual for values and procedures.

eddie jr

Well you can test the alternator output easily by testing the output terminal to ground with a multimeter or across the battery terminals. If you are only getting battery voltage then it is not putting out and something is up. I don't want to drive around knowing that it is not charging becuase that is asking for trouble getting stranded. You can also fry the battery that way too (heard of this many many times) and it is a fairly new battery so I don't want to potentially be doubling my cost.

My question is the rest of the wiring (essentially that circuit with the brown wire from the harness). According to my wiring diagram there is a resistance wire (10 ohm). Could this have been blown? What should the voltage be on this line in RUN?

Trickster

do you have a firebird or camaro?

eddie jr

Firebird....85....with guage not light.

Maverick H1L

iTrader: (8)

The wiring is most likely okay. Never rely on a 10-second bench test to tell you if the alt is good or not... I had my batt done three times and I am 99% sure it needs to be replaced, but its going to have to wait a while... People on here have been known to take a known bad alternator in for a bench test and have it PASS!

I did what you did twice, thats right, TWICE. The alternator's diode or rectifier or something got fried and it couldn't be fixed (case broke due to oxidation and weathering and general age when removing it) so I went out and traded the old one in for the 105 amp Duralast unit I have now, which works great.

eddie jr

I'm thinkin' it's gone but I just hate guessing, especially when I have no other car to get around....don't like wasted trips

Here is a strange one though, the brown wire at the alternator harness reads 11.99V. THe battery reads 12.01, so that appears to be battery voltage without any resistance as per the wiring diagram (says 10 ohm). What voltage should I be reading there with that 10 ohm resistance wire (sorry, a little rusty in the electrical department)?

HOw should I proceed?

eddie jr

anyone?

Maverick H1L

iTrader: (8)

http://www.autozone.com/servlet/UiBr...3d801c042d.jsp

Basic electrical theory should help you out...

eddie jr

cool link that i will definitely go through in detail when I have time but I am really strapped to get this thing back on the road. If someone could just tell me if I should be expecting something other than 12 volts on that brown wire and what it should be, that would be appreciated HUGE! Or tell me how i can caluclate it. At current I do not know how to calculate what is to be expected since you don't know the current on that line (you always need two variables to figure out the 3rd with ohm's law, correct??).

I don't understand how there can be a resistor on that line and still read battery voltage.....or if something blew, how you can read voltage instead of having a dead wire?????

stumped.....

eddie jr

anybody? still can't figure this out. So no one has ever tested that line to see what the voltage is?

Trickster

Okay,
Since you have the gages instrument cluster, you should be reading battery voltage at the brown/white wire at the ignition switch. You should also be reading 10 OHM's of resistance between that wire at the ignition switch and it's connection at the alternator. If you have that, then the problem if any lies elsewhere in the system. BTW, as mentioned in another thread that you have on the same subject. Since you have the 2.8L engine with the gages cluster, there is a 10 OHM (+ or - 1 OHM) resistance wire going from pin "F8" of the bulkhead connector C100 to the ignition switch. There is no Diode in that circuit for your car. Hope this helps you!!!!!!!!!

eddie jr

Ok, so battery voltage even though there is resistance on that wire. Cool thanks alot Trickster, that helps big time! I already have battery voltage so I will just check for the proper resistance in the morning and then off to get a new alternator (have bat voltage at the two red wires at the alternator as well).

Just curious though, why should there be 12v on that line.....I thought I read somewhere (can't remember for sure or where) that the full 12v is too much for the alternator on that line??? Did I misunderstand? What exactly does the 10 ohms do then??

Trickster

On the V6 VIN S & the V8 VIN F engines with gages, with the ignition switch in "RUN". Battery voltage is applied through the RESISTANCE WIRE and the Generator field (to ground). This provides initial Generator field current.
With the engine (GENERATOR) running. Field current is supplied directly from the stator's output through the diode trio inside the GENERATOR.

eddie jr

ahhhhhhhhhh, pooey! After getting a new alternator on the weekend I started it up tonight and guage is still reading below 12

I don't understand, I have 12v constant at the output terminal (with the wire connected of course), 12v constant at the little red wire in the harness and 12v ignition on the brown wire....yet it still doesn't work

What do you think it could be? What exactly is a "resistance wire" anyway? I assume it performs the same function as a resistor??? Is it possible to "Blow" one and yet get the full 12v through it (ie no resistance)??

Help!

Trickster

What voltage are you getting across the battery with the engine running? If there is a big difference in the reading, I would look at changing the voltage meter in the dash or checking its connections.

eddie jr

less than 12 across the battery (same as guage).

Trickster

Just for sh*ts & giggles, There is a junction block located behind the right headlight where wires running between the battery and alternator are connected. Take a good look at those connections for corrosion or a loose connection. The resistance wire is located under the left side of the instrument panel near the ignition switch. Have you used a multimeter to measure the resistance in it. Do you have any other systems that seem to be having some problems like maybe the coolant fans, how are they wired?

eddie jr

Ok I'll check behid the right headlight tomorrow morning before I head into work.

NO other systems "appear" to be acting up....other than the signals flash slow etc.

No I haven't tested the resistance wire for resistance yet. I just assumed it was ok since I read voltage at the alternator. How do you get tothe ignition switch though (seems impossible to get to in that tight column...doesn't it connect right to the switch or does it start at a harness at the base of the column?

Trickster

Yes it connects to the ignition switch and comes through the fire wall at connector C100 on the drivers side and the pin is "F8". Unless you are skinny and double jointed like I am, it would be a good idea to remove the drivers seat first.

eddie jr

ok did some testing:

-bat voltage at ouput terminal, red harness terminal
-switched bat voltage at brown wire in harness
-guage reads bat voltage with car on or off
-11.79v at battery when car running
-15.5v at ouput terminal with car running.

So 2 things:
1. is that 15.5 too high or is it ok and just over 15 because the regulator is only seeing 11.79 along that brown wire, thinks the battery is low and then puts out more to compensate?
2. It appears as though the problem may be that the output is not getting back to the battery......does this make sense??? But what i don't get is if i am getting bat voltage at the output terminal then that wire must be a complete circuit to the battery, so why can't the output get back to the battery??

i am going to check the junction block too but man it is hard to get at