I let the 2000 A4 coupe sit over the weekend, had to jump start on monday and then slow/ sluggish start on tuesday. Took the car by O'reilly's , Napa, and autozone and all three stated that after testing the battery was fine just needed a charge and the problem was with the alternator. All three stated that it was only putting out around 16 amps instead of the correct 110 amps. I bought a new 110amp duralast alt (part number 13381) from Autozone but kept the original to have rebuilt and chromed. Easy install... i mean it is just an alternator, the belt, two screws, and two wires and the new one was in... oh and 1.5 beers.... oh common.. it's after 6pm here and I had a rough day in clinic! proud of myself on a quick fix and cleaned up... went to start the car and everything sounds good and runs smooth until I check the DIC.... " charge system fault" is shown. what did I do? Or is it that this alt will not work correctly and will have to just wait until I get the old one back from rebuild? Anyone? Bill? I know you have the answer...lol..

 

only one code is present....

PCM p1638 H C

this is new, gonna go to vette dr and see what it is.

DIC still shows "charge system fault" after checking all connections. It shows up and then disappears and then comes back after like 20 secs... even shows check gauges in the HUD.

Anyone have any ideas?

thanks, Thomas

 

p1638 H C

this means there is something wrong with the generator F terminal circuit.... but I have no clue what that means... need some help here...

thanks again, thomas

 

ttt

 

ttt for the morning...

I think my biggest question is is it safe to drive while the original alt is being rebuilt or am I going to damage something while the other alt is being used temp and because of the "charge system fault"????

thanks , thomas

 

anyone know if it is safe to drive or not? common someone has got to know...

Thanks, Thomas

 

Mine started doing this about a month ago. I thought maybe it was the battery going bad so I replaced it and problem still exists. The charge system fault only comes on when car is first started. It acts like the voltage on start up is low and brings up the charge system fault. After a few minutes the voltage is reading a little over 13 and I hit the reset and all is ok. I find myself carrying around a spare battery because I don't know what to make of it. I amagine the Alt is going bad and will fail at sometime. Who knows when. I hope someone can shed some light on this.

Ron

 

yeah sounds like the alt is failing....probably something to do with the little diode that is on the f terminal going back to the PCM from the alt. My alt was only producing 16amps instead of the 110amps... anyone else have any ideas? Is my car safe to drive for awhile like this?

 

The wire that connects to the back of the alternator is known to go bad prematurely on our cars. As long as the car is starting and charging I don't see the problem being the alternator. Might want to check into the wire.

 

You will be fine driving it around like this, the REF to the computer is not working so it thinks you are going to kill the BAT. Your problem most likely lies with the Alt, it is an Autozone POS. Hope this helps.

 

Would this be the large red wire or the wires with the clippie?
Ron

 

The PCM monitors the alternator through the red and grey wires .Read the description below:
The L-terminal circuit from the generator is a discrete circuit (a discrete circuit has no splices and only one source and destination) into the PCM. The PCM applies ignition voltage to the generator L-terminal circuit. A small amount of current flows from this circuit through the generator windings to ground to create a magnetic field which starts the generator process. When the generator is at operating speed and producing voltage, a solid state switch for the L-terminal circuit in the generator opens and the PCM detects that the initial startup current flow has stopped.

The PCM expects to detect low voltage on the L-terminal circuit prior to the generator rotating at operating speed and conversely expects the circuit to be at ignition voltage potential when the generator is operational. When the PCM detects a fault (circuit shorted to ground, or circuit shorted to voltage), the Driver Information Center will display Charging System Fault.

The generator has an input to the PCM called the F Terminal to indicate the percentage of total capacity that the generator is producing. This signal is detected by the PCM as a duty cycle from the generator and displayed on the scan tool as a percentage. The PCM can monitor the generators output under all conditions to determine if it is functioning normally.

When there is low demand from the electrical system on the generator, a low duty cycle percentage will be displayed. As more accessory load is placed on the generator, the duty cycle output detected by the PCM will approach 100 percent. A normally functioning generating system will never reach 100 percent as indicated on the scan tool.

The L and F terminals are the red and grey

hey 50th... hope this helps you understand, it pointed a lot out to me... just as mant other of Evil Twins posts have... He always has a great explaination and provides great detail....

Thanks Again ET.... you da man....

 

Thanks Sully
That is great info.
Ron

 

The wire I was speaking of is the clip one that sits on top of the alternator. It dosen't make a good connection after time.