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Which one is alternator output connection at starter relay?

Paisano

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I have a 92' Ranger XLT with 2.9 V6. I need to test my alternator/voltage regulator for excessive voltage, with my multi-meter. The instructions in the manual say connect the positive lead to the alternator output connection at the starter relay. I included a photo of the starter relay. Which one is the alternator output connection?

P_20211002_104205_001.jpg
 


Uncle Gump

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Any B+ point will work. But it is whatever side of that starter relay that is connected to the battery.
 

Paisano

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I don't understand, Gump. What is a B+ point?

See the larger red wire coming out the split loom tubing connecting to that forked relay harness? That cable comes from the battery. But I don't know which side of the relay is connected to the battery
 

RonD

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On the back of the alternator is a stud/nut terminal, largest wire or 2 wires are connected there, that's called the B+ terminal

In 1992 that wire(s) on B+ runs to Starter relay on inner fender, connected on the same post as Battery Positive cable, should be several other wires on that one post

The B+ wire to starter relay has a Fusible link at the starter relay end that can blow/melt

Alternator B+-------------(wire)-------------------------------(fusible link)-Starter relay post

Key OFF
You would test B+ terminal for Battery Voltage(test battery FIRST)
Use the alternators metal case as the Ground for volt meter
If B+ shows battery voltage, EXACTLY, then the wire/fusible link are OK

If voltage is lower, even a little, then move Volt meters ground to Battery Negative
If volts come up to Battery Voltage then you have a bad Negative battery connection

With engine running
Just test voltage at the battery, should be no higher than 14.8volts, and no lower than 13.5volts
If higher replace alternator
If lower test other 3 wires on alternator


Starter relay
It will have two larger posts
One will be connected to Battery Positive by a larger cable, that post is the 12volt distribution point for ALL the vehicles 12volt power
So this post will have several wires on it, including the alternators B+ wire

The other larger post will have ONE CABLE, to starter motor, nothing else should be on that post

It will have 1 or 2 smaller posts
EACH will have a letter next to it, an "S" or an "I"
The "I" post is no longer used, since the early 1980's
The "S" post will have 1 wire connected, it comes from the ignition switch in the cab, it activates this relay which then activates the starter motor

Since the "I" post is no longer used a new starter relay may or may not have it, doesn't matter, as long as it has the "S" post it will work fine
And yes "S" does stand for START
"I" was for ignition/spark system, just FYI

And the larger posts are interchangeable, since "I" post is no longer used
So there is no Battery Positive post or Starter motor post
As long as ALL the other wiring is on with the Battery positive cable and the Starter Motor cable is on its own on the other larger post, all will work fine
 
Last edited:

RobbieD

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Left-hand large post in your picture. Visual clue, is that terminal has multiple wires, including the constant power to your underhood fuse/relay box. And, to verify it, your meter will show +12 volts on this post, regardless of the starter being engaged or not. The other post has + 12 volts only when the starter is engaged.

Just follow @RonD 's advice, and you'll be golden.
 

Paisano

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Ok. Let me take some time to read through this.
 

Paisano

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Ok. I read all of this carefully and I am pretty much done with the multi-meter testing. The testing procedures I used from my manual were a little different than Ron's
But Ron's tutorial was very helpful. Results below.

Two days ago, I got 14.98 battery volts on my multi-meter with engine idling

Just now the readings for the A and F voltage regulator terminals on the alternator were exactly the same...............which means bad voltage regulator
I also checked for bad connections and bad grounds and did not find any.
 

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I don't understand, Gump. What is a B+ point?
I don't want to confuse the issue if you're on the right track to test charging system voltage.

But Battery Positive voltage (B+) is a constant wherever it is found in the vehicles electrical system.
 

Paisano

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Ok. Thanks for adding that Gump. That is probably one of the key points to help in my understanding of the charging system.
 

Paisano

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Oh. I see what you're saying now Gump. I was just following the instructions exactly and it said if the voltage on the two regulator terminals were the same, the voltage regulator is faulty. (black probe touches the rear alternator housing...........while positive probe touches A terminal then positive probe touches F terminal marked 'ground here to test.'

I forgot to say. I also did Ron's test where you compare battery voltage to B+ terminal voltage, Both were exactly the same.
 
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Uncle Gump

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Yeah... I confused things for you.

You probably did the test right... I was simply making a general statement about B+.
 

Paisano

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No problem Gump. It just made me double check my work.

The only NEW 'plug-and-play' alternator I can find is a 3-5 day wait. It's online order through a major auto parts chain. What if I drive it a little longer with an over-voltage condition (about 14.98 volts)? I only have the one vehicle.
 

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No problem Gump. It just made me double check my work.

The only NEW 'plug-and-play' alternator I can find is a 3-5 day wait. It's online order through a major auto parts chain. What if I drive it a little longer with an over-voltage condition (about 14.98 volts)? I only have the one vehicle.
Not great. Prolonged overcharging will "cook" the battery and ruin it.

Just to clarify. When you first start the engine, battery voltage should be around 14.5-14.8 volts. After it has been running a few minutes, it should come down around 13.5-13.8 volts.
 

Paisano

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I tested the battery after running the engine more than 5 minutes (while parked) and I got 14.98 volts.This was two days ago.

For some reason last night, the voltmeter in dash panel finally showed normal indication and light pulsating calmed down after days of excessive voltage
 

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The fatt bastard wire.
 

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