Voltage issue?

[TuRBoTaLooN]

Having some voltage issues. A few weekends ago I drove the car to new brunswick and it was running ok. When I got there, the windows wouldnt go up and I couldnt connect to DSMLink. I checked the voltage (via my turbo timer) and it was under 12 volts. I think DSMLink cant connect under 12 volts. So I figured the alternator died. I barely made it home and removed the alternator and the battery. Took it to Advanced Auto and they said the alternator was completely dead. So they replaced it for free, and charged the battery. So today I got around to putting it all back together and I started it up and it started fine. I tried to connect to DSMLink but again it could not connect. Windows also would not go up. The voltage was like 11.6. So I drove the car for about 15 minutes and the voltage actually dropped down to like 11.2. I have no idea where to start troubleshooting this one. Any ideas?

 

[UK-DSM]

I suspect that the ECU is no longer controlling the alternator (telling it to apply charge). If you have a known good battery and alternator and you do not have a battery light lit on the dash while engine is running.

The control is the 4 pin connector on the alternator. Pull it and make sure the wires are not damaged etc.

Other things to check are alternator fuse for continuity.

 

[ntdsmr87]

idk if the ecu would do that my bet would be on the voltage regulator i think its on the fire wall i dont think the ecu controls that at all a voltage regulator is.... is an inductor and inductors oppose to change in current and voltage so watever the value is i think is between 12.6 and 14 volts it should regulate that voltage it shud be attached to one of the alternator wires good luck....im really good with wiring im an avionics tech so shoot me pm if u have ?'s

or the regulator might be on the alternator as well

 

[UK-DSM]

I think you will find the ECU controls the alternator charge. And with the signal disconnected the alternator will not provide charge. The regulator regulates voltage over rpm.

He has installed a new alternator. The regulator is within the housing of the alternator.

 

[ntdsmr87]

signal of what dc? direct current has no frequency at all so idk where that would come from but i know the ac signal is rectified by the diodes inside of the alternator.....but ## right i could happen idk anything

 

[UK-DSM]

Read this please.

Here's your Hz less output from a normal alternator. I can count 1/t.

 

[ntdsmr87]

yea u got me....i forgot about pulsating dc................good job....

 

[UK-DSM]

I was not out to get you man! The alternator is excited by DC from the ECU to control charge. Most cars are dumb and everything is alternator controlled as you described. The 2g is a PITA, if the ECU sends no signal the alternator is basically off line. This appears to be what the problem poster is describing.

This is one reason why the Saturn swap is so popular.

 

[steve]

The OP's issue is with a 4G63. (The manual page above is for a 420A.)

On a 2G Turbo the ECU can control the output of the alternator by grounding the G terminal to turn the field off just like the internal voltage regulator does. If the connection is open the alternator should be running strictly off the regulator. The reverse of what you described from what I understand but since I don't have a 2G I'm just going off the FSM.

The ECU also monitors the FR terminal to sense when the alternator is active so it can adjust the ISC/IAC to maintain the idle speed.

The specifics are in the 2G Technical manual and the 2G FSM.

 

[TuRBoTaLooN]

Thanks for the detailed information guys. So it looks like my diagnostic steps will be as follows...

1) Check wiring harness to alternator
2) Check fuse
3) Check alternator (many people have told me stories of getting dead ones right out of the box)

Any other suggestions?

EDIT:

Another thought. If the battery was JUST recharged, shouldn't it produce at least 12v to the system?? Could this point to another issue?

 

[steve]

Another thought. If the battery was JUST recharged, shouldn't it produce at least 12v to the system?? Could this point to another issue?

If the battery was just fully charged it should have at least 12.6v on it. The voltage right after charging can be higher do to float. Remember to check at the battery posts and then at other places on the car. Any major difference indicates a connection/wiring problem.

 

[TuRBoTaLooN]

Yea, I should really get a volt meter. Could this be from a bad ground?

 

[steve]

That's one possible cause.
Have you cleaned and inspected all the cables to the battery?

 

[TuRBoTaLooN]

No, I really need to take a good look at the wiring. I have a funny feeling that my external dump tube fried a bunch of wires near the alternator.

 

[steve]

If it's that close then the heat isn't good for the alternator too.

 

[TuRBoTaLooN]

Yes, unfortunately my turbo setup is not ideal. The FP turbo has the wastegate off the compressor housing and it's a Tial 44 so it's pretty big which means the dump tube that goes straight down is VERY close to the alternator. I mean it's got some high temp coating on it from JNZ, but it's not ceramic coating, and I have heat wrap on it, but it gets stupid hot. It's literally almost touching the slim fan on the driver's side and pretty much melted most of that. So I really need to sit down one weekend and figure out a way to have this set up and not burn through stuff so quickly and keep temps at a reasonable level while driving.

It almost makes me want to start over, haha.