Diesel Alternator is magic!

The place to discuss problems and routine maintenance questions and tips. This is for topics that are specifically diesel-related.
User avatar
81dieselrodeo
Regular Member
Posts: 25
Joined: Thu Apr 23, 2009 12:25 am

Diesel Alternator is magic!

Postby 81dieselrodeo » Fri Apr 24, 2009 8:49 am

OK, here's the deal.

I'm insane. I had a friend yank the engine and trans out of my rusted to oblivion 81 LUV 5 speed shortbed.

The alternator was working tip-top at that time.

It now lives in a 1994 Rodeo.

I've 'invented' my own system for starting the motor. Ford Starter Relays for Glow Plugs and Starter. Switch for fuel cut-off solenoid on the IP. Works great, engine fires up and runs.

But I can't for the life of me figure out how to make the alternator crank out some juice. I don't want to start hooking wires up to ground/12V at random, cuz that might blow it up.

I've read that the alternator is internally regulated.... So why does it have a screw terminal plus a plug with 3 wires, and no juice when the engine is running?

What do I have to 'invent' to make this alternator crank out charging voltage?

Unfortunately, the friend I had yank the engine doesn't believe in wires. All the old stuff from the LUV is long gone. Grumble.... What sort of cheater, jumper, etc do I need to make so that the alternator will turn on and charge my battery?

Annoying first post, huh?

Pupfocused
Regular Member
Posts: 790
Joined: Tue Oct 16, 2007 2:14 pm
Location: Portland, OR

Re: Diesel Alternator is magic!

Postby Pupfocused » Fri Apr 24, 2009 10:26 am

Check the brushes
Jim
1981 diesel pup
1985 4X4 diesel pup
1986 diesel trooper

User avatar
JoeIsuzu
Site Admin
Posts: 17421
Joined: Thu Aug 19, 2004 9:11 am
Location: Germantown (next to Elvistown), TN
Isuzu vehicle(s): Original owner, '83 LS Diesel, 5-spd, 2wd, Long Bed, restoration in progress!

Re: Diesel Alternator is magic!

Postby JoeIsuzu » Fri Apr 24, 2009 10:45 am

What parts of the factory system do you have? Do you have the charging relay?

Jack

User avatar
81dieselrodeo
Regular Member
Posts: 25
Joined: Thu Apr 23, 2009 12:25 am

Re: Diesel Alternator is magic!

Postby 81dieselrodeo » Fri Apr 24, 2009 11:03 am

I read .20 volts from ground to the screw terminal on the back of the alternator. To be expected from 'idling' field coils. No idea if I'm reading ground to ground, but that terminal appears to be insulated from the casing. So I guessed that's where my charging current is supposed to come from. Also, it seems like the only connection able to handle reasonable charging current as well. Something in that 3 wire plug must be for 'turning it on.' The mention of a charging relay seems to mean I'm right about that. But I don't feel like experimenting when a replacement alternator costs over $150.

One of the wires must energize a field coil, another must monitor voltage, and the 3rd slaps the juice on from the screw terminal. Makes sense anyway... But which is which?

Brushes, new. I had nothing to complain about before it was removed from the LUV. Worked perfectly.

Charging system. I have the alternator, and that's it. Everything else was scrapped before I got a chance to audit it... Grrr...

User avatar
81dieselrodeo
Regular Member
Posts: 25
Joined: Thu Apr 23, 2009 12:25 am

Re: Diesel Alternator is magic!

Postby 81dieselrodeo » Fri Apr 24, 2009 8:21 pm

I guess I'm just going to have to risk the unit and explore. Everything I read is about wire colors on another truck, but not what any of those wires actually do or connect to.

Lets see if I get any comments on this theory:

I'm guessing that 1 wire goes to 12V to energize the field coil. A second one is a level output that, when high enough, convinces a relay to trip, which applies juice to the 3rd wire, which activates output to the screw terminal.

I guess I'm going to apply 12V to 2 wires at a time in the 3 wire connector, until I read ~13V at the screw terminal. And pray I don't blow up anything. This will 1) apply juice to field coil 2) emulate perpetual positive input from charging relay. 3) leave the level output unconnected and unmonitored. With 3 wires, I've got a 33% chance of getting it right. Not great odds, so I hope the unit is resilient and doesn't blow up if I hit one of the 2 66% probable 'wrong' combinations. A.k.a., apply 12V to the level output in my random sticking of probes...

Then, if that works out, I have to figure out if any portion of that circuit is closed when the key is removed.

Gerald K4NHN
Regular Member
Posts: 1209
Joined: Thu May 29, 2008 10:37 am
Location: Cayce, SC

Re: Diesel Alternator is magic!

Postby Gerald K4NHN » Fri Apr 24, 2009 8:23 pm

Here is a diagram from a service manual for the alternator on an 82 Luv, it should be about the same..One is the 12 volts to excite the alternator, one is the output and the other one is for the charge relay. The IG and S may be stamped on the housing some where, but I've never looked at one in hand. It looks to have the regulator built inside the housing. Hope this helps. With an ohm meter that has a diode position on it, you should be able to ohm out the terminals and tell which is which.
Attachments
Isuzu alternator.jpg
Gerald K4NHN
Cayce, SC

"One test is worth a thousand opinions"

1983 LS DIESEL LONG BED 2 W/D 126K miles

1986 LS Trooper Tubro Diesel 4 W/D 186K + miles

User avatar
81dieselrodeo
Regular Member
Posts: 25
Joined: Thu Apr 23, 2009 12:25 am

Re: Diesel Alternator is magic!

Postby 81dieselrodeo » Fri Apr 24, 2009 8:26 pm

Gerald K4NHN wrote:Here is a diagram from a service manual for the alternator on an 82 Luv, it should be about the same..One is the 12 volts to excite the alternator, one is the output and the other one is for the charge relay. The IG and S may be stamped on the housing some where, but I've never looked at one in hand. It looks to have the regulator built inside the housing. Hope this helps. With an ohm meter that has a diode position on it, you should be able to ohm out the terminals and tell which is which.


Brilliant, thanks muchly!

According to that diagram, L, S, and IG appear to be the designations for this mystery connector's wires. After looking at it a few times, I'm not sure how this circuit works.

Only thing I'm really sure of is that L controls the "Charge Relay" and it doesn't do anything but turn the dash light on and off. It's normally open, so this means that energizing it turns the light on, and lack of juice turns the light off. It appears to cheat and use a satuartion principle to do this. It must be a very precise relay, probably gets finicky when it gets old, or connections get a tad crunchy... very likely to give a "false positive" for telling you the alternator isn't charging, when it actually is.

IG appears to apply power to the Regulator. S confuses me, as it appears to be a perpetual dead-short through D12... Then, uh.... R3 and R2 slowly drain the battery until it is dead, any time the engine is not running.... ,:-/ I hope R3 and R2 are REALLY big.... F is internal? L is the wire I'm going to ignore and leave unconnected, since it really doesn't do anything but provide human data via the dash light.

Since IG is intended only to be energized when the key is on, I need to be able to tell the difference between the two inputs needing 12V.

As you say, Gerald, I should be able to figure it out with the MM. I suppose I'll tie IG to the Fuel Cut-off Solenoid, as soon as I figure out which one that is... ;-) No, just for good measure... That S connection bugs me, being a completed circuit from +12V to Ground at all times, key in or not. I'll put them both on the switch. It might be a guarantee against capacitance.... But I'll try it my way first.

User avatar
Paul
Regular Member
Posts: 906
Joined: Thu Nov 25, 2004 11:14 pm
Location: Central Calif Coast

Re: Diesel Alternator is magic!

Postby Paul » Sat Apr 25, 2009 12:07 am

Hi--

Here is a complete wiring diagram for the '84 diesel. You will need to click on it to download the full size and clear version.

viewtopic.php?f=1&t=5190&hilit=wiring+diagram&start=15

This should help you figure what is what.

Paul
'84 P'UP 2 wd diesel, 5 spd with 0.78 fifth gear and differential back to 3.73.

User avatar
81dieselrodeo
Regular Member
Posts: 25
Joined: Thu Apr 23, 2009 12:25 am

Re: Diesel Alternator is magic!

Postby 81dieselrodeo » Sat Apr 25, 2009 4:01 pm

That's awesome.

This diagram confirms more of what I was thinking. The "Charge Relay" is properly referred to here as the "Charge Warning Relay." Many of it's connections are independent of the actual charge circuit, and it works on a principle of coil saturation. It probably gives a lot of false positives, telling the driver that the battery is not charging, when it actually is just fine. But more importantly, I'm not using it.

IG is also called IGN, and connects to the ignition switch rail, which provides +12V any time the switch is in the on position. S is an always-connected-to-12V wire... Which feeds through an internal diode and 2 resistors, to ground... I still don't like that.

But I still don't know what color IG and S wires are, unless....

S = WL (on truck) White w/ ?Lavender? Stripe?
IG = W (on truck) White?
L = WG (on truck) White w/ Green Stripe?

The wires are labeled in the diagram with those letter codes, possibly representing colored wires. But they are labeled only on the "truck side" of the connector. There is no guarantee that the wire colors on the alternator would match. It's possible and reasonable, but not certain. The replacement alternator from [generic auto parts store] most definitely does not comply with these color codes.

Can anyone who still has an original ignition/key switch verify that they have a white wire labeled "IG" or "IGN" going into the back of the ignition switch? Just a quick look under the dash it all it should take.

Gerald K4NHN
Regular Member
Posts: 1209
Joined: Thu May 29, 2008 10:37 am
Location: Cayce, SC

Re: Diesel Alternator is magic!

Postby Gerald K4NHN » Sat Apr 25, 2009 8:27 pm

I looked in my 82 Luv book and the color code chart shows

WL = White-Blue
W= White
WG- White-Green
WR= White-Red
WB= White-Black
WY= White-Yellow

This is on the Charging Circuit
Gerald K4NHN
Cayce, SC

"One test is worth a thousand opinions"

1983 LS DIESEL LONG BED 2 W/D 126K miles

1986 LS Trooper Tubro Diesel 4 W/D 186K + miles

User avatar
Mike Beard
Regular Member
Posts: 174
Joined: Fri Apr 06, 2007 8:41 am
Location: polk city, fl between tampa & orlando

Re: Diesel Alternator is magic!

Postby Mike Beard » Sun Apr 26, 2009 11:37 am

this is how I wired my alt. in my 91 gasser pick-up with an 84 2.2 diesel

gasser diesel

white(12g) white w/blue stripe(12g?)

white w/blue stripe(16g) white w/green stripe (16g)

white w/yellow stripe(16g) white(16g)

this has been working for me for the last 2 years

mike
aka-Bigdog

91 2wd- 223 n/a ,5speed ,3" body lift
05 colorado, wifes car

rjm
Regular Member
Posts: 355
Joined: Sun Oct 19, 2008 5:08 pm
Location: Los Angeles, CA

Re: Diesel Alternator is magic!

Postby rjm » Mon Apr 27, 2009 2:52 pm

Paul wrote:Hi--

Here is a complete wiring diagram for the '84 diesel. You will need to click on it to download the full size and clear version.

viewtopic.php?f=1&t=5190&hilit=wiring+diagram&start=15

This should help you figure what is what.

Paul

Paul,

That diagram got converted to jpeg and the resolution isn't good enough to print like you recommend. The file size is 92KB. Do you still have the 3 MB file available for d/l'ing?

Thanks,

Riley
1984 P'up, 5 speed
2wd long bed diesel
Just turned 70K!

User avatar
JoeIsuzu
Site Admin
Posts: 17421
Joined: Thu Aug 19, 2004 9:11 am
Location: Germantown (next to Elvistown), TN
Isuzu vehicle(s): Original owner, '83 LS Diesel, 5-spd, 2wd, Long Bed, restoration in progress!

Re: Diesel Alternator is magic!

Postby JoeIsuzu » Mon Apr 27, 2009 3:18 pm

rjm wrote:Paul,

That diagram got converted to jpeg and the resolution isn't good enough to print like you recommend. The file size is 92KB. Do you still have the 3 MB file available for d/l'ing?

Thanks,

Riley

You have to click on it to display the full-size one. It's 6358x4437 pixels / 3.24Mb. You can THEN download it if you want.

Jack

User avatar
81dieselrodeo
Regular Member
Posts: 25
Joined: Thu Apr 23, 2009 12:25 am

Re: Diesel Alternator is magic!

Postby 81dieselrodeo » Mon Jun 08, 2009 11:49 pm

OK, I thought I had it figured out....

I have 12V going to IG and S, from battery.

When charge terminal is disconnected, it reads 18V. It pulls down to about 14V when connected to the battery.

But after driving about 50 miles, headlights, cooling fan, cut-off solenoid all powered: battery is dead. A jump start doesn't help. The cut-off solenoid falls and cuts off the engine as soon as the jumpers are removed. This a brand spankin' new battery.

Charge terminal still shows me 18V when disconnected, and 14V when connected to battery. But the battery is not charging. It's totally dead.

I put the charger on it when I got it home. Recharged the battery (it took a charge easily), and repeat. Same results.

How can this be so?

Gerald K4NHN
Regular Member
Posts: 1209
Joined: Thu May 29, 2008 10:37 am
Location: Cayce, SC

Re: Diesel Alternator is magic!

Postby Gerald K4NHN » Tue Jun 09, 2009 1:03 am

When everything is connected and you're measuring the 14 volts, is that at the battery, or where? A battery with 14 volts applied to it will be taking a charge if it's a good battery. But if the demand on the battery is more than what the alternator is putting out, then the battery will go dead. ie, if you're pulling 40 amps out of the battery and your alternator is only putting out 20 amps, then you have a negative 20 amp on the battery and it's slowly going dead. You need to measure the current draw from the battery with everything on and also with everything off that you can turn off and see how much current in going into the battery. A good starter, generator shop can measure it. The regulator may be holding the current down and not keeping up with the load. With the engine shutting off when the cables are taken off tells me that isn't hardly any current going to the battery from the alternator...
Gerald K4NHN
Cayce, SC

"One test is worth a thousand opinions"

1983 LS DIESEL LONG BED 2 W/D 126K miles

1986 LS Trooper Tubro Diesel 4 W/D 186K + miles


Return to “Diesel - Troubleshooting and Maintenance”

Who is online

Users browsing this forum: Duck and 1 guest