pulling my last hairs out-help (1 Viewer)

Joined
Apr 9, 2020
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Gatineau ,Quebec, Canada
I replaced my alternator shipped from australia in my '89 hilux surf 2LT.
Not charging. I have new fully charged batteries. Ive checked all the wires replaced and a couple of connectors at the battery.
I yanked the seat did the limbo under the dash and cannot find a dud wire or circuit. AT my whits end...what are the chances the new alt is bad out of the box? what else should I be lookin at. I there a relay in the fuse block I should be checking? Any help or wisdom greatly appreciated!
 
Joined
Jul 11, 2015
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414
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Las Vegas
If you are wondering about just the alternator take it out and to an auto parts store where they can bench test it. Check fusible links, make sure they didn’t burn or just break from old age and wear.
 
Joined
Oct 20, 2017
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542
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Salt Lake City
Give this a read and make sure your new alternator is regulated the same as the old one (internal vs external)
 
Joined
Mar 25, 2014
Messages
20
I'm not sure if its the same, but I had a similar problem in a 93 4Runner. There is one of the bigger fuses in the box under the hood that goes to the alternator. It is bolted in from underneath, so you cant just pull it out. Luckily I had a spare in my parts bin because I couldn't find it for sale anywhere.
 
Joined
Apr 9, 2020
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Gatineau ,Quebec, Canada
My alt is internally regulated, and I replaced it with the exact same kind. It will go to the shop today to be bench tested. I hope the seller in Australia warrenties it turns out to be a dud.
 
Joined
Apr 9, 2020
Messages
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Gatineau ,Quebec, Canada
Update, alternator bench rest confirms perfect function so it is a wiring issue. I have a three wire plug plus the battery . Battery is fine and the wire is good between the batt and alt. The other three are IG , power from the ignition switch, L for dash light and S for sensor. Now the fun begins!
 
Joined
Sep 11, 2012
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567
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Vancouver, B.C.
Not sure for the surf but somewhere on here should be a link for the wiring diagrams. Mine is for a 1990 gas pickup, but it looks to be similar. I have the same 3 wire plug. I'm investigating where exactly they all tie into the circuits.
 
Joined
Apr 9, 2020
Messages
17
Location
Gatineau ,Quebec, Canada
Not sure for the surf but somewhere on here should be a link for the wiring diagrams. Mine is for a 1990 gas pickup, but it looks to be similar. I have the same 3 wire plug. I'm investigating where exactly they all tie into the circuits.
My three plug harness has a wire from ingnition, dash light and Sensor.

s-l400.jpg
 
Joined
Apr 9, 2020
Messages
17
Location
Gatineau ,Quebec, Canada
Update, alternator bench rest confirms perfect function so it is a wiring issue. I have a three wire plug plus the battery . Battery is fine and the wire is good between the batt and alt. The other three are IG , power from the ignition switch, L for dash light and S for sensor. Now the fun begins!
Checking the power to the vehicles wiring harness that plugs into the alternator, the S connector shows battery voltage with ignition off and in ON position-as it should, The IG conectors show zero with ign switch off and 12v with ign switch on -again as it should. The L connector shows zero with ign off and 12v with ign on.
Im thinking that is not correct, should it not read zero volts? Could the problem be the ignition switch?
 
Joined
Apr 9, 2020
Messages
17
Location
Gatineau ,Quebec, Canada
I'm not sure if its the same, but I had a similar problem in a 93 4Runner. There is one of the bigger fuses in the box under the hood that goes to the alternator. It is bolted in from underneath, so you cant just pull it out. Luckily I had a spare in my parts bin because I couldn't find it for sale anywhere.
all the fuses seem fine, no duds.
 
Joined
Sep 11, 2012
Messages
567
Location
Vancouver, B.C.
i'm on a similar path with an alternator. I just printed the diagram gnob posted. It printed fairly well off the screen here. Much simpler than the long foldouts in the FSM.
 
Joined
May 24, 2015
Messages
140
How do you know its not charging?

When you turn the key on, does the alt light on the dash come on?
And then when the truck is running, does the dash light go out?

I think the function of the light is that it gets 12v from the ignition and when not running it is grounded at the alternator. After starting the engine the alt loses ground at that pin and the light goes out(indicating the alt is charging). Then if the alt/reg craps out while running the alt pin becomes grounded turning the light on indicating alternator problems.

If the light works as it should but youre not measuring 14.0-15.0V volts at the battery while running I'd check the circuit between the alt output and the battery. Or check the output stud of the alt directly with the engine running.
 

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