Alternator Harness issues

Lil Freek

Member
:
'01 pro lx-t
I'm looking for some quick feedback.

I should note that I'm wire/electronics retarded and learning my way up. I have the Haltech installed in the car, and it all works fine when I disconnect the ground to the alternator - when the ground is connected, I get a pulse in voltage in the batter from 12.5V to 15V.
My car's been off the road for over a year due to some stupid problem. I didn't try to really tackle it last year, and this year, I'm bound to fix it.
I'm pretty sure I've found the problem, actually - but I need some confirmation.

I'd be super grateful if I could get some feedback from a few people on this, just so that my theory is fully confirmed. I'm going to be calling a couple local dealerships and a Mazda Racing dealership to confirm, too.

I need someone to test continuity between the ground(s) for the alternator and the ground/negative terminal on the battery. I tested this on a Protege5 on Saturday and got continuity - tested on my car, nothing... there's SOME connection, but there's some resistance stopping the wire from getting full continuity.

Tools required to help:
2.0L protege without cruise
Multimeter

Set the multimeter to test continuity via BEEP.
Connect one end of the multimeter to either of the ground clips that connects to the alternator, connect the other end of the multimeter to the terminal that's connected to the negative battery terminal. Once one clip is tested, test the other clip on the alternator ground wire.
Does it beep?

When I tried on the Protege5, it beeped with one of the alternator clips, but not the other, which I'm pretty sure is how it's supposed to work - that's how the voltage regulator works, to my understanding. On my Protege, it didn't beep with either clip.

Thanks to anybody that can help :)
 
If I have time, I'll run out and see what I can find tonight. Just as a side note, since you're running a haltech...doesn't the ecu regulate the voltage? I know most newer alts have a built in regulator, but I thought I remembered reading somewhere that ours doesn't and that it is controlled by the ecu. So, depending on how your standalone is wired, the ecu would no longer be regulating the voltage, hence the fluctuations you're getting. Could this be the problem, or am I way off base? Never really dealt with engine management/ecu tuning, so I'm not positive. But none-the-less, I will try to check for continuity tonight.
 
Just so I'm straight as far as which terminal to check, on the attached diagram, is it clip 1 and 2? Looks to me as tho clip 1 is the only ground going to the alt.
 

Attachments

  • alternator.pdf
    239.6 KB · Views: 180
Last edited:
i thought that the voltage regulator was apart of the alternator on the 99 and newer model protege?
 
yes, the alternator has something like a voltage regulator built in... but mazdas have the ECU control the voltage regulation, for some unknown, stupid reason.

sam1 - 1 isn't a ground, 2 is the ground.
 
yay!
Thanks man :D

I'm going to buy wire tomorrow and see what I can fix.
It sucks, too, my car's at Brian MP5T's house, but it's not like I can use his monstrosity of a car as a blueprint :eek:
 
well that makes a lot of sense.. I have been having this problem where the car wants to cut out on me, when using alot of power like radio and heat ext... and sometimes for when i am not using any of those features. and I have changed the alternator with a new one, but they are both fine, as well as the voltage regulator. I bet my problems are coming from the ecu then. If I do have the problem where the ecu is causing this do you think that i have to replace the whole computer?
 
ya... from my understanding, you can't just fix one part of the ECU... i have a spare one, luckily... and i know where I can find a couple extras for dirt cheap, so i'm not overly worried.
 
I didn't get any continuity on terminal P and quite a bit of resistance on terminal D. Measured 1.3xx on the digital multimeter. Wires appeared to be about 12ga.
 
I just went out and rechecked since I thought it was wierd that I got continuity on the opposite side you did. Same result, measured 1.376 to be exact. Only thing I can think of is that you have the two wires transposed...
 
If your reading anything..THere is continuity.
OL or O.L would be open..or no continuity.
The beep is not neccesarily the only way to see continuity.....If the resistance is higher than what the meter deems as direct contact..the Buzzer/beeper will not sound...Yet you can still have continuity..It just depend on the circuit and its layout.

Check this site out..Its interesting to say the least. you will learn something from it I am sure.
 
The image of Terminal D and P, that's when I'm looking at the terminal, right? So if i unplug the terminal and look at it head on, terminal P would be the one on my right, right?

Would it be weird if i had the continuity backwards? I found my spare ECU, so I'm going to plug that in and see if it works with just a different ECU.
 
I'm going to have to take out the entire harness and peel apart the alternator harness and check each wire for continuity/resistance, that's what today will entail. It's def. something along that harness, and i'm going to be damned if i don't find out what it is.

Any other ideas to the possible problem?

I'm looking for another alternator that I can borrow to test out a potential bad alternator. It was NIB, though, so one would hope it's not bad :eek:
 
The image of Terminal D and P, that's when I'm looking at the terminal, right? So if i unplug the terminal and look at it head on, terminal P would be the one on my right, right?

Would it be weird if i had the continuity backwards? I found my spare ECU, so I'm going to plug that in and see if it works with just a different ECU.

Yep, you got the terminals right, that is if you're looking at the terminal with the clip facing upwards. I can't see the alternator being bad, since you said it's fluctuating between 12-15V. So it's definately doing something, just not doing it right, lol. Are those wires leading to the ecu even touched during the Haltech install? Only thing I can think of is they got switched around. I don't think it's a short, because if it were, you should be reading cont. on both terminals, wouldn't you think? The link to the manual that you posted..it had some instructions on how to check each individual terminal for voltage. Maybe try that and see if it's within spec. Do you have the wiring manual that accompanies the FSM? If not, I'll scan those pages and post them as attachments as well. But looking at it, it seems that wire 4, aka terminal P, wire colors W/L lead TO the ecu, and wire 2/terminal D/wire colors LG/W lead FROM the ecu to the alt. Don't know if that helps any. If you would like me to post those pages, let me know.
 
please do post those.
I'm going to Brian MP5T's house, today (in an hour), to work on my car, so i'll just be checking this board and the shop manual for help as i'm working away.

I'll be checking the voltage, for sure, as shown in the manual.

No alternator wires should have been touched in the installation of the Haltech, so they should all be good. I'll have to test the wires from the engine bay to ECU.

I'll just start with replacing the ECU (easiest thing to try) and go from there. The problem must be with those terminals, though, because the pulsing goes away the second I unplug it. So if the terminal goes directly to the ECU, I'll have to trace those wires all along the alternator harness and probably engine harness and find where the problem is.

do you know what the pin numbers are for the ECU harness?
 
Heres the wiring diagram. Pin #s look like 30 and 53
 

Attachments

  • alt wiring diagram.pdf
    58.1 KB · Views: 214
Nice... i'll check all those out.
Seems like I have a hefty afternoon ahead of myself :)

Thanks for all the help - i'll report back throughout the afternoon, see if this can get dealt with today. It kept the car off the road for an entire summer, not allowing that to happen again.
 
Back