Alternator problems, low voltage - 2000 GT

[Nghtrdr]

Hi all
Need some help diagnosing an alternator ploblem I seem to have.
I had to replace my altinator as it was on the way out. So decided to upgrade and had a new 160amp unit made. It didn't produce anything over 13.5v even above 2000rpm. The shop did a few tests in the vehicle and decided to make another one. The replacement would make 13.3v. Again even above 2000rpm. The decision was made to get away from the 3 phase alt altogether and go denso 6phase. The hope was the denso uses a completely different regulator and is a much better alt all around. Well installed it yesterday and guess what, it only makes the same 13.5v as the previous two. These are not rebuilds, these are brand new alts.
Testing has shown its not a ground or power wire issue. They were jumped from the alt to the batt with no change. This eliminates the cables. The sense/trigger wires were tested for proper power on the harness and all seems well. I am completely stumped with this issue. Three brand new alts, 1 totally different, can't be bad.

Any ideas would be very helpful before I go out of my mind. Lol


Thanks
Dan

[Ponyryd]

Have you tried a different battery?

[ZR]

Agreed on battery.
What are you measuring voltage with?

[Nghtrdr]

Batt has been swapped. Mine is in perfect condition and at rest is 12.7v
Snap on test equipment was used to load the alt at the shop that made the alts.
I've personally used my sct tuner to monitor as well as a fluke volt/amp, ac/dc volt meter

[RedSN]

13.5V
How many volts are you aiming for? Pardon my ignorance, but isn't 13+ volts a healthy alternator?

[ZR]

When running have you checked..........
-output voltage at the alternator itself using it's case as a ground source then using battery as a ground source?
- hooked an aux ground lead from alt case to battery?
- checked small wire inputs for voltage when running?
- bench tested alt output?
- does alternator light work?
- run battery low to see if alt voltage rises?
- running at say 2000 rpm, turn on headlights and blower fan, what does voltage do?

Your below optimum but it's not horrible either.

[WidowrRacing]

I recently replaced the stock alternator on my 88GT...I figured it was well passed due and would be a great upgrade.

After being replaced with a new 130 amp from LMR with it's own 4 gauge power fusible wire. I now have the light on the dash and it charges at 13.3.
I even used the stock alternator pulley it came with and not the under drive alternator pulley I installed years ago.

I find it strange the dash light appears now after the upgrade.
The battery is also fairly new.

I'm going to remove the alternator and have it checked over by an alternator shop.

[ZR]

3G style alt?

[WidowrRacing]

In the LMR SVE ad it states:
This alternator is from the internally regulated 3G series.

comes with a **Limited Lifetime Warranty**

Item #SVE-17046K2

[Ponyryd]

Batt has been swapped. Mine is in perfect condition and at rest is 12.7v
Snap on test equipment was used to load the alt at the shop that made the alts.
I've personally used my sct tuner to monitor as well as a fluke volt/amp, ac/dc volt meter

12.7 is over voltage. Is that with a surface charge? Could have a bad cell there.

[Nghtrdr]

13.5V
How many volts are you aiming for? Pardon my ignorance, but isn't 13+ volts a healthy alternator?

14.1 is the lowest a healthy alt should be. Some will say 13.8v-14.8v. 13.5v is below norm

[ZR]

Did you run down the check list I put up?

[Nghtrdr]

Batt is good and has been tested. Batt is an odyssey high output, low resistance batt. Has always been 12.4-12.7v since day one. Btw I have two of these batts and both run at the same voltage..
Alt harness wires test good.
Alt has been beech tested ok. (14.5v output)
Alt in the car, grounding and power wires jumped and tested good. Even went so far as to sand motor mounts where the alt bolts up.
Alt has been load tested in the vehicle with everything on and does not rise above 13.5v. It has even been load tested using an snap on alt load tester.. No change

The alt is able to charge the batt at this level but my gauge lights dance to the radio. So not enough to output to keep everything in check. The second last alt would cause the batt light to come and go. This last one isn't doing that and is giving some amps. Just not anywhere near what it should be


Thnx

[Nghtrdr]

Did you run down the check list I put up?

Yes Rick. Everything has been tested when the alt whent in to try to figure out why in the vehicle it's not giving proper voltage and amps. No faults or reason could be found.
Something is missing from the check list that is causing the issue.
Please see above

[Ponyryd]

Well what is the difference from them testing it to it being in your car? It's either the cables, battery or control that's the issue. A battery is made up of 6 cells at 2.1v each, it should not be above 12.6v unless a surface charge is present.
Has your battery been load tested?
Did you swap out the battery with one with proper voltage?
What voltage is the car commanding to turn on the alt? Further, what voltage is their test equipment commanding?
What if you run the car and disconnect the battery, what does the voltage spike to? (Do this only momentarily to get a reading, this will full-field the alternator and kill it quickly if you do it for a too long)

[ZR]

Backing up, if alt bench tests at 14.5, 110% it's the car.
As said above, did you try a conventional battery that has correct static voltage?
Does your replacement dash have the correct resister for the alt light?

[ZR]

With alt mounted to the vehicle.
-bypass trigger wires (use loose plug vs one on the vehicle) - results
-bypass 12v feed to battery - results
-bypass ground to battery - results
-test with conventional battery - results (based on what your experiencing, I'd do that first)
-if none of the above makes a change on their own, do all at once. Now one by one, remove and hook up vehicle wire until you find the one thats making the difference.

[Nghtrdr]

As stated the batt was swapped and tested from another vehicle. Same output. Yes the batt has been load tested as well. All good. The 12.7v reading was an hour after a run with the car, so prob had a surface charge still. The batt is not the issue. It has been eliminated from the equation at this point.
I agree it's something in the car.
The cables (power/ground) have been jumped eliminating them from the equation. I'm personally leaning towards a bad harness connection. Although the wires test for voltage ok. I'm thinking the connections are not good. It's the only thing that has not been changed yet.
Going to try cutting off the harness and soldering in a new one tomorrow if it doesn't rain.

Thnx

[ZR]

Unplug harness from the alt, use a plug from the wrecker, remote trigger.

[ZR]

Alt wiring diagram (save to your computer / open to view from there)

[Nghtrdr]

Unplug harness from the alt, use a plug from the wrecker, remote trigger.

Can u explain a bit more please?
I know one wire is from the batt and should read batt voltage. What does the other go to?

[ZR]

Heading to bed, take a look at the download I posted.

[Nghtrdr]

Sorry Rick. Pain meds kicking in. Thnx for the help
I'll look at it tomorrow with a clear head.

Have a great night