PorscheFanatic202

Just did the nissan quest alternator modification and it works great now. I don't even have to "blip" the throttle to get the alternator to start charging.

However, now I have an ANTILOCK light and "!" warning light on. No other lights.

Voltage is right at 14V on the dash (13.8V on a multimeter).
It lights up with the key in the ignition and stays on after engine start. Not just when moving (as would be indicated by a failing sensor). When dealing with the alternator/battery connections does it affect the anti lock braking system?

I still need to jumper the relay connections to test if its a relay issue, but i'm doubting this because I took it out yesterday and stomped on the brakes on a wet road to see what happens. It feels like the ABS is working fine.
Any thoughts? Anybody have the ABS Test Plan handy?

Teddy952

I used the link below to test all 4 ABS sensors. With minimal effort I was able to figure out which sensor was faulty.

https://rennlist.com/forums/924-931-...-resolved.html

PorscheFanatic202

all four tested fine. All 1000 ohms +/-20

PorscheFanatic202

Checked fuse 26. All good.

Tested relay. All good.

Jumpered power relay G20 - pins 30-87 - I can hear the other relay in the right fender clicking when i power it. Start car and still ABS light is on. Current draw is 0.45A between those pins (relay power, 30-87)

Checked continuity between relay power (87 on relay to pin 1 of harness) - All good, low resistance.

Checked grounds to computer (pins 10,20, and 34 on harness) - All good.

Checked hydraulic equipment resistance from harness.
Pins 32-18 - 1.2 ohms
Pins 32-35 - 1.1 ohms
Pins 32-02 - 1.2 ohms

I think the last thing to check are the two relays at the ABS unit itself. I am kinda trying to avoid opening that area up, but it seems like i'll have to.

Any ideas?

PorscheFanatic202

Anybody else have this issue after the alternator mod? I'm about to buy a new ABS computer.

Reading through this write-up....

http://www.porsche968uk.co.uk/techni...abs-refurb.php

...sounds like alternator voltage sensing might be an issue.

"Pins for the ABS Relay
Pin 15 is the voltage sensor from the Altenator."

Other than that, all the relays check out with flying colors. Pump works, grounds cleaned, but still the light. Perhaps there is a wire that normally connects from the alternator to the ABS unit. Anybody have experience?

Lastly, are there any compatibility differences between 928-618-118-00 & 0-265-103-013 ABS computer units?

Oddjob

For what it is worth - I do know that the ABS brain is sensitive to low voltage, and it will be one of the first systems to fail when the alt/battery is going out.

PorscheFanatic202

It's interesting you say that. Just today my alternator stopped charging intermittently. I could tell because the engine revved up a little higher without the load of the alternator and the voltage simultaneously dropped to slightly under 12V (Battery voltage). But the ABS warning lamp and the Central Warning Lamp went out with the drop of the alternator. I never got an Alternator light though.

PorscheFanatic202

so today i decided to tackle this issue head-on. I grabbed the WSM and sifted through all the electric diagrams to find the fault. I never really made a conclusion of what the problem was. I got stuck checking the continuity between the blue wire to the alt (which is apparently connected to pin 61 of the alarm, which I jumpered) and pin 61 of the alarm control unit. I assumed I was reading something incorrect on the diagram and went ahead and assumed the alt was bad. I wanted to test the coils directly. I took the alternator apart and tested both the exciter coil and the main coils. The exciter was around 2ohms and each of the mains were like 0.2 ohms (really 0 since my cables read about .1 - .2). So it was fine. Put it back together and decided to provide +12 V to the exciter and the alt provided 13.9V, and after I disconnected that exciter wire it jumped to 15V !!!!! I checked the blue wire voltage and it is now reading near battery voltage when the ignition is on and now my alternator works flawlessly and the ABS light is out and works. I don't know what I did, but it seems to be working now. I'm almost certain it will come back in a few days.

PorscheFanatic202

On the drive home, as expected, the alternator stopped charging again. This time I was far enough away for the battery to not let me make it home and the car eventually shut off about 15 min into the drive home. I tried to hard wire the exciter wire to the lead of the battery with no success. AAA'd it home.

I did a few tests when I got home and I did notice that when I turn the ignition on, the alternator warning lamp doesn't illuminate. I pulled the cluster and tested the lamp by applying 12v across pins 3 & 4 of the connector. The lamp works and the circuitry going to the lamp works. Does this just mean that there has to be a break at some point between the lamp and the exciter wire terminal? I'm chasing the diagrams now, but getting stumped.

If someone could chime in with knowledge, it would be much appreciated.

Noahs944

Your writing style and comments make you sound like a technician. Good job on tackling this frustrating problem. I enjoy wiring problems... but not with my 944. Damn Germans!

Sometime the most difficult electrical gremlins to chase are due to a crappy ground. In my work I find if I'm finding inconsistency and non-sense, then I will turn my attention to ground. The theory being if the ground is weak then the device (light, load, etc) is getting a ground through the path of least resistance, which sometimes is through the positive wires.

A quick and fun way to test this theory is to use jumper cables with alligator clips from the batt's neg to the device (alt, body ground, light, etc). Takes no time at all but will put my mind at rest.

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I'm glad you tested the instrument panel bulb. Sometimes a failed bulb will stay on.

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Did you determine the alt regulator was faulty?

Are you certain the Alt has a proper ground?

PorscheFanatic202

I figured out that the alternator field circuit is bad. I happened to keep my stock alt with a new voltage regulator. I placed both on the bench, wired up a 12v light to the field circuit and tested both. The Nissan Alt didn't even light the bulb up (just like on the car) but the Porsche one did. I spun both with a drill and the lamp went out on the Porsche one. So I put that back into the car and called it a day. I'll send the other one back for an exchange in a week or so. I'm slightly fed up with the company since they don't believe my diagnosis and want me to have a shop test it.

ried

Thanks for documenting this!