alternator wiring problem/ Please help!!! - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 08-27-2005, 12:12 PM
junglejeep
Guest
 
Posts: n/a
alternator wiring problem/ Please help!!!

Hello all,

I am about a year into my rebuild of my 79 CJ7 and I have come to a problem. I rewired the entire rig by hand for starts. I have done a lot of research and I believe the correct alternator wiring is as follows:

BAT terminal to constant hot side of starter solonoid.
#1 terminal to the neg. side of a switched indicator lamp.
#2 terminal to constant 12 volt (on the battery) for sense.

I should also state that I have a Sunpro amp meter in line on the charge line, to the solonoid.

When I hook the wires up like this, the indicator lamp is on, and the alternator does not charge. The battery just runs down.

In my experimenting, I have found that if I hook up the #1 terminal to constant 12 volts, switched or not, the alternator charges at a rate of about 30 amps, according to the meter, and the jeep maintains 14 volts at idle. This seems correct but why does it work, if the wires are hooked up wrong? Also, when hooked up this way, the BAT terminal gets very hot. Is this tricking a faulty alternator into working? Or is the battery just really dead and this terminal would only be hot until it is recharged? According to the amp meter instructions, the meter should only really read less than five amps at idle.

Please help, I want to be back off-road soon. Its been a year, and I am getting hyper!!!!!!!
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 08-27-2005, 12:55 PM
 
Join Date: Sep 1999
Posts: 5,383
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: alternator wiring problem/ Please help!!!

Quote:
"BAT terminal to constant hot side of starter solonoid.
#1 terminal to the neg. side of a switched indicator lamp.
#2 terminal to constant 12 volt (on the battery) for sense."

OK so far...
#2, should be the larger of the two wires, and can attach to constant or switched sources...

NO MENTION OF DEDICATED GROUND FROM ALTERNATOR TO BATTERY...

No mention of a fusible link inline at the starter solenoid either...
------------------

Quote:
"I should also state that I have a Sunpro amp meter in line on the charge line, to the solonoid."

Now here is a problem...
There is a reason not much comes with an 'Amp Meter' anymore.
Unless you have a 'Shunt' type Ammeter, this may be your problem. The 'Amp Meter' can't handle charging systems over about 35 or 45 amps, and most of us have larger alternators (and loads) than that.
If you have a 'Shunt' type ammeter, the shunt can be causing problems.
Both the amp meter and the shunt can have grounding out issues, and if either one goes (depending on system) it will look all for the world like a bad alternator.
That's why most of us use volt gauges instead of trying to use amp meters.
---------------------

Quote:
"When I hook the wires up like this, the indicator lamp is on, and the alternator does not charge. The battery just runs down."

What kind of 'Light' do you have in your system?
Most light sockets ground through their housings, and if this is the case, it's the light socket doing bad things to your system.

See, the #1 wire is the excite wire, and it supplies current to the voltage regulator to get things started.
When the alternator is not generating (as in stopped) this terminal is a GROUND, and your light is 'ON',
BUT...
When the alternator starts to produce, that terminal becomes 12 volts POSITIVE!
This means if you have a bulb socket that grounds through the housing, you are grounding out the regulator!
What was a ground, keeping the light on, is now positive and the light goes out, but you can't let that circuit go to ground at the light or the regulator can't work.

Look for a socket that has two wires and a plastic housing or insulated housing.
The socket you use must have a CONTROLLED GROUND, and that ground must be attached to the #1 terminal.
You can also try installing a diode at the #1 terminal, with the stripe facing the alternator.
-----------------

Quote:
"In my experimenting, I have found that if I hook up the #1 terminal to constant 12 volts, switched or not, the alternator charges at a rate of about 30 amps, according to the meter, and the jeep maintains 14 volts at idle."

This would reinforce what I'm thinking about the bulb socket.
With 12 volts straight to the #1 terminal and no resistor you are going to get continuous 'Full Field' effect from the alternator, and it's going to overcharge the battery.
------------------

Quote:
"This seems correct but why does it work, if the wires are hooked up wrong? Also, when hooked up this way, the BAT terminal gets very hot. Is this tricking a faulty alternator into working? Or is the battery just really dead and this terminal would only be hot until it is recharged?"

You are pretty sharp, done your homework...
You ARE tricking the alternator into producing at the limits of it's ability.
Battery terminal will get very warm (not hot) unless you are over charging it, throwing AC current at it (if the diodes in the alternator are bad), or the connection is faulty (not tight, crud covered, corrosion in terminal or on batt post) or the battery is shot...
-----------------

Quote:
"According to the amp meter instructions, the meter should only really read less than five amps at idle."

Five amps is normally about the 'Running Drain' of the average vehicle, with all accessories off.
I'm still leery of Amp Gauges. Like I said, the entire current from the alternator runs through there, and if something goes wrong with the amp gauge, it's going to look a whole lot like a bad alternator.
-----------------

Here are the recommendations,
1. Take your alternator to the local auto parts store and have it tested. (free)
2. Charge the battery with a battery charger before trying to diagnose the vehicle. (free)
3. Run an 8 or 10 gauge ground wire from the back of the alternator to the negative terminal of the battery. At least as big a wire as you used for the 'Battery Charge' wire. (appx. $2)
4. Install a 12 gauge fusible link in the master charge wire at the starter solenoid. (appx. $3)
5. Take your light socket out of it's mounts (so it can't reach a ground) and see if the problem corrects it's self. If so, you need a controlled ground light socket.(between $3-$10)

Time to test the system...

And now...
6. Install Radio Shack p/n 276-1144 diode with the stripe facing the alternator.(appx.$2)
(there will be a stripe on one end of the diode)
This is a safety feature that keeps your charging system from going to hell if the light wiring gets grounded out again.
Junk Yard Genius is offline  
post #3 of (permalink) Old 08-30-2005, 12:44 PM
junglejeep
Guest
 
Posts: n/a
Re: alternator wiring problem/ Please help!!!

Well,

I took the neg wire off the battery and checked the voltage between the neg wire and the neg terminal on the battery and discovered about 12.3 volts. I thought I may have a short somewhere so I started digging. I quickly discovered that the cd players back-up power was causing the voltage indication. It is a back-up power line to the radio to keep the presets and stuff, so this reading may be ok???

Back to the alternator,

I cleaned the Weber carb and adjusted the idle down to about 700 rpms. The voltmeter on the dash now says about 13 volts at idle which is ok because it is down the line a little. The battery tests about 14.6 on the handheld voltmeter. All seems well, except for the fact that I do not have an indicator lamp to the #1 terminal of the alternator. The BAT terminal does not get hot unless I rev the engine and it begins charging (at about 30 amps). At idle it is about 4-5 amps on the amp gauge. If I remove the #1 terminal wire, and test the terminal while the engine is on, it is putting out no volts.

Putting a switched 12 volts to the #1 terminal, without an inline light seems to make everything work, so should i worry?
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 08-30-2005, 04:32 PM
Way Outta Control
 
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: alternator wiring problem/ Please help!!!

Let me see if I have this clear:

At idle it doesn't charge.
If you rev it it will charge but not as much as you'd like.
Measduring at the #1 alternator plug shows very low volts -- at idle?

Sounds to me like it's the diode trio inside the alternator. Easy way is just replace the alternator. If you take it to an autoparts store where they test it - it'll show good - they don't test that part of it. They do like you did - full 12v volts to #1 and rev it up. The kids pronounce it "good."

The #1 terminal (disconnected from everything else) should show 12 volts when it's running - even if charging very slightly.
RRich is offline  
post #5 of (permalink) Old 08-30-2005, 04:44 PM
Way Outta Control
 
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: alternator wiring problem/ Please help!!!

By the way - sounds like you wired the ammeter wrong too.

You have it like:
alternator --- ammeter --- battery/load

You have the ammeter is SERIES with the alternator.

It should be the alternator feeds the load, the ammeter goes between the battery and load.
battery -- ammeter -- load/alternator

That way, the alternator can feed the load with however much it needs. Whatever the alternator can provide ABOVE THE LOAD REQUREMENTS goes to the battery to recharge it - if needed according to the "sense line."

The ammeter reads what's going in, or out of the battery.
Notice an automotive ammeter usually only goes up to 30 amps (far less than an alternator can put out.
That's because the battery can only accept about 30 amps charge without burning up. Your load could be much much more than that.
All you need to know is if the battery is charging or discharging, and about how much.

I've noticed some of the cheapie Chinese ammeter's instructions show it wired wrong too.

If you want to monitor the alternator amp output, you'll need an expensive industrial ammeter capable ogf more than the alternator - and it doesn't really tell you anything important.
RRich is offline  
post #6 of (permalink) Old 08-30-2005, 04:52 PM
 
Join Date: Sep 1999
Posts: 5,383
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: alternator wiring problem/ Please help!!!


See #1 in "Recomendations" (sic)

No charge at low RPM, and he doesn't have the #1 terminal hooked to anything, or just not to a light (resistor)?

RRich, didn't we JUST go through this?... [img]/ubbthreads/images/graemlins/wall.gif[/img]

Ask for advice, but don't listen to it... [img]/ubbthreads/images/graemlins/spank.gif[/img]

Is it just me or am I missing something here?
Junk Yard Genius is offline  
post #7 of (permalink) Old 08-30-2005, 05:41 PM
Way Outta Control
 
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: alternator wiring problem/ Please help!!!

Unless I misread the thread, heb did have it hooked up at first. Last post he took it off and measured it.

The #1 feeds the diode trio, then the fields.

Key on, engine off - the idiot light, being tied to the ign, provides current to the fields to get things started. Not running the #1 should read 0.

But once it starts turning and charging, that #1 goes high - to 12 volts. Then both sides of the idiot light is at 12v, no current flows through the bulb, bulb stops glowing. But it's charging now.
At slower speeds the alternator slows down, if you look really close, the bulb starts glowing a little - because now current is flowing a little again, making the alternator restart.

Yes -- we sure did! But I think this time the prob's a little different, close, but not exactly.

Funny - just the other day I was looking at a friend's Chevy truck. I noticed sparks coming from the alternator bracket!
Bolts were loose - and tightened on paint! Sure supports the reason for a separate ground wire, at least to the block.
But then - if he had the ground wire I wouldn't have noticed the sparks! The bolt would have fallen out for bigger problems.
Can't win for losin'!
RRich is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome