RB25DET - Quest Alternator || Overcharging 16+ volts

[BlueRB]

I have an rb25det with an 99-02 Nissan quest alternator upgrade. The previous alternator went out and I am not sure of the make and model. It was from the previous owner of the vehicle. My problem is that I had the Nissan quest alternator on for about 2.5 months. Took out my FC controller one night and looked at the screen and noticed that I was overcharging to 15-16 volts consistently before I could make it home the battery let go and started smelling of "old eggs."

*@ Idle its 12.1 - 12.5
*When throttle is pressed at any point it spikes to 15.4 - 16.3 and sits there.

Since then I have changed my grounds, got an exchange for the alternator because someone told me the 'rectifier' could have possibly gone bad. Replaced the battery checked over wires. *Purchased a voltage stabilized (20$) mistake.

If anyone has a clue to what I have done wrong in this process please inform me what to purchase or what to 'wire' in to make it work properly and not over charge. (Spare me the flame if possible)

(Pictures)
Side question someone also informed me that there should only be 1 thick white wire. I have two is this normal ?

[Ramius83]

Re-check with a multimeter first. Two wires could be going to other things, ie fuse box, starter, etc, just depends on how they wired the car. Wouldn't make a difference in regards to over charging voltage. Where are you getting the alternators from? Could be another bad one.

[Carl H]

bad regulator.

[BlueRB]

The alternators were picked up from advanced autoparts

I would hate to push my luck and return it a second time. I don't want them to see that it isn't for my year/make/model. I had to slightly shave a side.

I am just trying to get a definitive answer. Also is it true that "Nissan Quests" have an external regulator for voltage?

[Carl H]

its been several years since cars had external regulators and stranger things have happened...those reman ones are hit or miss.

[BlueRB]

It wasn't remand I am pretty sure it was new but I get what you're saying.

If you know anyone selling a rb25 alternator let me know

[robbie2883]

i have a 6 month old rb25 alt. gonna pm you.

[Darius]

I had a refurbished Quest alternator go bad right out of the box. Exchange it for a different one.

[Carl H]

i got a brand new alternator off ebay for 75$ shipped, still trucking along since i bought it 5-6 years ago.

[BlueRB]

I bought robbies

It didn't work neither 120$ down drain

I can't figure this problem out now it idles at 11.8 and spikes to 15.4

Anyone has any suggestions to did this please let me know

[Carl H]

what lower harness are you using?
might want to troubleshoot the charging system using the 240 diagnostics.

[silviamadness]

I am having exactly the same problem right now with my RB25 S14. The car starts (rough) and charges and 12.6 volts, when the throttle is touched it goes to 15.5 volts and stays there. The plug on the side has two wires, the Aqua wire reads 12.6 volts and the other reads .38 volts. This was discovered the same way you did as well, through reading the consult gauges through the EMS. Did you resolve this yet?

[silviamadness]

I have an rb25det with an 99-02 Nissan quest alternator upgrade. The previous alternator went out and I am not sure of the make and model. It was from the previous owner of the vehicle. My problem is that I had the Nissan quest alternator on for about 2.5 months. Took out my FC controller one night and looked at the screen and noticed that I was overcharging to 15-16 volts consistently before I could make it home the battery let go and started smelling of "old eggs."

*@ Idle its 12.1 - 12.5
*When throttle is pressed at any point it spikes to 15.4 - 16.3 and sits there.

Since then I have changed my grounds, got an exchange for the alternator because someone told me the 'rectifier' could have possibly gone bad. Replaced the battery checked over wires. *Purchased a voltage stabilized (20$) mistake.

If anyone has a clue to what I have done wrong in this process please inform me what to purchase or what to 'wire' in to make it work properly and not over charge. (Spare me the flame if possible)

(Pictures)
Side question someone also informed me that there should only be 1 thick white wire. I have two is this normal ?

If you are still having this issue, check the circuit which goes to the warning lamp on the gauge cluster, which is the White/Red wire. I found this out oddly, when I overlooked looked the fact that my gauge cluster was not in the car. Hope that helps

[G-E]

One of those small wires on the secondary plug goes to the positive wire in the harness far enough away from the alt so as not to read ripples... the alt then uses that as a reference whether to boost/lower voltage, my guess is that wire or junction is corroded and the alt is thinking the volts are lower than they really are

[Darius]

This is not related to your problem, but I'd recommend putting a larger power wire on the alternator. Those two little wires can't possibly support the amp draw of the engine plus accessories especially if you have electric fans. Each of my electric fans has a power wire that thick and it still gets warm.

[OutToWinPAHC]

Alternator has 3 wires, battery/12V+, regulation, and charge lamp. With the car running unplug the small wires and check them to vehicle chassis ground with a volt meter. You should see voltage 12-16 in your case on both wires. If you dont then there is the problem, the regulator diode bridge is running, but the voltage regulation circuit is off.

[BlueRB]

Sorry for the late reply.


- PROBLEM IS SOLVED -

The plug in the back of the alternator did have enough power going to it. So in turn it could not tell the alternator what to regulate the power. Gave it a 12v source boom fixed issue.
Now I have 1 extra brand new alternator if anyone needs an upgrade for their RB HMU.


Thank you everyone at nicoclub

[Flatline1121]

SO. Im having a similar situation to this with my car. S14 chassis with an rb25det s1. The chassis harness is practically non-existent short of what i have begun wiring.

in any case, the Alt has 12v to both wires in the 2pin plug. In my plug its a wht/red and 14awg white wire. Both have 12v when car is running. The wht/red "field" wire has 12v but the alt still acts like it doesn't. (alt doesn't charge until the engine is revved up)...

When the alt is charging it charges 18.5v. Metered at the alt post, both plugs in the 2 pin, at the fuse block in the car, and about a half volt drop at the battery in the trunk.

Ive ripped apart the lower harness (not sure what the harness is from) and double checked the wiring and it looks good.The ground for the alt is run into the car and grounded to the aftermarket fuse panel i have installed so its not that.

I feel like ive covered all my bases here. Does that pretty much mean the regulator is shot? or is there something im missing.
I read somewhere something about a wire to the alt needing 6 volts and not 12 somewhere? could that be a part of it?
There is not wiring in the engine bay except the engine harness and lower harness. everything goes through the firewall (tube front on the car when i got it so no relays or fuse block underhood either)