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Discussion Starter · #1 ·
I recently replaced my old alternator with a new one. The new one isn't charging my battery, however. I've checked the connections and the belt, and they both look good. My gauge cluster is acting very strange as well. The battery light comes on, but my gauges don't seem to be receiving any power while the engine is running. The battery gauge is at 0, along with the tach. I haven't driven it yet, so i'm not sure if it's the same for the speedometer too. With my old alternator, I was at least getting the gauges to work, although it wasn't charging since the pulley was seized.

I've done a few tests to try and diagnose the issue, but I'm a little lost. Here's what I've done so far: 1) Battery reads in the mid to low 12 volt range while the engine is running. 2) with ignition on and the engine off, there is no continuity and voltage between the positive wire in the engine bay fuse box, and the alternator post. 3) With the engine running, there's no voltage between the positive wire and the alternator post (forgot to check for continuity).

Any ideas on what might be happening? I'm a little confused about why the gauges have completely stopped working now. I can't tell if there's a blown fuse somewhere, if I broke a wire in the alternator plug, or something else. I've been told to also check the chassis ground to alternator post connection, but a little confused on where the chassis ground is (first car I've worked on). Would appreciate any ideas or other tests to do. Thanks!
 

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I recently replaced my old alternator with a new one. The new one isn't charging my battery, however. I've checked the connections and the belt, and they both look good. My gauge cluster is acting very strange as well. The battery light comes on, but my gauges don't seem to be receiving any power while the engine is running. The battery gauge is at 0, along with the tach. I haven't driven it yet, so i'm not sure if it's the same for the speedometer too. With my old alternator, I was at least getting the gauges to work, although it wasn't charging since the pulley was seized.

I've done a few tests to try and diagnose the issue, but I'm a little lost. Here's what I've done so far: 1) Battery reads in the mid to low 12 volt range while the engine is running. 2) with ignition on and the engine off, there is no continuity and voltage between the positive wire in the engine bay fuse box, and the alternator post. 3) With the engine running, there's no voltage between the positive wire and the alternator post (forgot to check for continuity).

Any ideas on what might be happening? I'm a little confused about why the gauges have completely stopped working now. I can't tell if there's a blown fuse somewhere, if I broke a wire in the alternator plug, or something else. I've been told to also check the chassis ground to alternator post connection, but a little confused on where the chassis ground is (first car I've worked on). Would appreciate any ideas or other tests to do. Thanks!
Take a look at the connector plug for the alternator, make sure those wires aren’t broken.

I had to fix mine about 2 weeks ago.
 

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Checked the ECU fuse in the engine bay fuse box, as well as the ECU-B and Alt Sencing fuses in the frunk fuse box and none of those are blown
AM2 7.5A fuse
ECU-IG 7.5A
ALT Sensing 7.5A

It seems you already know where to look.

Yeah starting to think that I might've broken a wire from the plug, so I'll definitely look there to see what's happening
Check continuity of these wires back to the fuse box in the engine bay.
Pin 17 White w/Red EA3 which is the long plug
Pin 4 Yellow EA3
Pin 7 Black w/Yellow EB1 which is the smaller plug
 

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Discussion Starter · #8 ·
AM2 7.5A fuse
ECU-IG 7.5A
ALT Sensing 7.5A

It seems you already know where to look.


Check continuity of these wires back to the fuse box in the engine bay.
Pin 17 White w/Red EA3 which is the long plug
Pin 4 Yellow EA3
Pin 7 Black w/Yellow EB1 which is the smaller plug
Definitely didn't know them off the top of my head lol. Thank you google. When you say long plug and small plug, what exactly do you mean by that? Are those certain areas in the alternator plug itself?
 

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Definitely didn't know them off the top of my head lol. Thank you google. When you say long plug and small plug, what exactly do you mean by that? Are those certain areas in the alternator plug itself?
Being able to find information is a good skill!!

Sorry, let me clarify.
The alternator 3 pin plug has those 3 wires on it. But to check that there are no breaks in them, test the pins in the alternator plug and the fuse box.

Long plug is red, Small plug is blue
Font Schematic Parallel Rectangle Plan


Pins as noted previously

Rectangle Font Line Parallel Engineering
 

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Discussion Starter · #10 ·
Being able to find information is a good skill!!

Sorry, let me clarify.
The alternator 3 pin plug has those 3 wires on it. But to check that there are no breaks in them, test the pins in the alternator plug and the fuse box.

Long plug is red, Small plug is blue
View attachment 83116

Pins as noted previously

View attachment 83117
Not an issue at all and thank you for the deeper explanation there. No worries if you don't know this, but do you happen to know which wires in those harnesses match up to the "terminals" in the alternator plug? Can definitely just mess around with them if I have to, but thought it was worth asking
Automotive tire Nail Automotive wheel system Tread Gas
 

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Not an issue at all and thank you for the deeper explanation there. No worries if you don't know this, but do you happen to know which wires in those harnesses match up to the "terminals" in the alternator plug? Can definitely just mess around with them if I have to, but thought it was worth asking View attachment 83122
Are you able to see wire colours? They should match up but if not.
Pin 1 being the horizontal one closest to the clip/bottom of the photo should got pin 17.
Pin 2 being near your thumb, pin 7
Pin 3 being the opposite pin 4.
 

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Discussion Starter · #13 ·
Are you able to see wire colours? They should match up but if not.
Pin 1 being the horizontal one closest to the clip/bottom of the photo should got pin 17.
Pin 2 being near your thumb, pin 7
Pin 3 being the opposite pin 4.
Thank you so much! The 3 plug wires are enclosed in a plastic/rubber sheathing that basically goes right to the plug and even where you can see the wiring, they're super dirty, so it's pretty hard to tell the colors apart
 

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Discussion Starter · #15 ·
One last question. I know typically when testing wires for continuity, you have to pierce the insulation around the wires. I've heard that can lead to corrosion over time, though. Just wondering if there's a way that I can just stick one of the probes from the multimeter directly into harnesses (eb1/ea3 in this case) to avoid that issue. I assume I might just have to just pierce the insulation, but thought I'd ask to be sure
 

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Discussion Starter · #16 ·
One last question. I know typically when testing wires for continuity, you have to pierce the insulation around the wires. I've heard that can lead to corrosion over time, though. Just wondering if there's a way that I can just stick one of the probes from the multimeter directly into harnesses (eb1/ea3 in this case) to avoid that issue. I assume I might just have to just pierce the insulation, but thought I'd ask to be sure
Ok never mind I assume i could just unplug the wiring harnesses and then put one multimeter probe in the harness and do the testing that way
 

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One last question. I know typically when testing wires for continuity, you have to pierce the insulation around the wires. I've heard that can lead to corrosion over time, though. Just wondering if there's a way that I can just stick one of the probes from the multimeter directly into harnesses (eb1/ea3 in this case) to avoid that issue. I assume I might just have to just pierce the insulation, but thought I'd ask to be sure
Remove the harness plug from the fuse box and alternator and probe the pins rather than damage the insulation.
 
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