Alternator or Cables?

[brmurph]

I am having an intermittent charging problem that seems to be getting worse over the last few days. For a while once the car was warmed up everything worked fine but now it seems even after the car warms up I am still having intermittent issues. The problem first appeard the day I left Texas but no problems until I got to Northern Minnesota. Now it seems to be fairly cronic but still intermittent (so it is much worse a week later).

Some history - The altenator was replaced 13 months ago for the same codes (I think same codes?) with AC Delco from gmotors.com (called them and it is one month out of warranty so no help from them :-( Still love those guys though..

Codes are IPC B1911 - Generator L-Terminal Problem and PCM P1638 - Generator F-Terminal Circuit

Messages are - "Battery not charging" and "Service charging system"

Voltage is a about 14 when working and 12 when not. So far the battery has not been run down (car still drives) but I have not gone long distances once I arrived in MN.

From searching the archives this would most likely be an altenator problem or possibly battery cables. I am thinking it is probably an altenator (even though it is only 13 months old) but since I am traveling and would like to fix it the first time I thought I would check with the board and see if any one agrees. Cables look great from the outside and terminals are clean.. Also reset all connections both at the altenator and battery (did not help)..

Thanks!!

[BodybyFisher]

DTC B1911 Generator L-Terminal Problem

Circuit Description

This test is only performed when the ignition switch is in RUN, the IPC measures an engine speed above 600 RPM, and the vehicle diagnostics system is not activated. This DTC indicates that a circuit malfunction is preventing the alternator from charging the battery.

Conditions for Setting the DTC

The IPC determines that CKT 225 is grounded by the generator with the ignition switch in RUN and the engine speed above 600 RPM.

Action Taken When the DTC Sets

The IPC displays the BATTERY NOT CHARGING message and illuminates the BATTERY indicator.

Troubleshooting Hints

This DTC typically indicates a malfunction within the generator.

Check for battery voltage at the generator terminal L (with the engine running). If voltage is present, check for intermittent shorts or opens in the alternator L-terminal or ignition-1 circuit. According to the print below the L terminal is ("B") Circuit 225 (RED WIRE).

DTC P1638 Generator F-Terminal Circuit

Circuit Description

This diagnostic DTC is used to monitor the field voltage of the generator. The generator is able to produce the desired voltage by varying the duty cycle of the field current. At low engine speeds, the field may have a duty cycle of 90%. At higher engine speeds and lower electrical loads, the duty cycle will be less. The generator produces a PWM signal that is monitored by the PCM on CKT 23 at connector C1 terminal 54. This signal duty cycle is sent to the PCM and if it falls below a certain duty cycle for too long, DTC P1638 will set.

Conditions for Running the DTC

Engine has been running for at least 60 seconds

Engine speed between 500 and 3000 RPM.

Conditions for Setting the DTC

Generator F-terminal duty cycle is 5% or less for 20 seconds.

Action Taken When the DTC Sets

The Malfunction Indicator Lamp (MIL) will not illuminate.

The PCM will command a message to be displayed.

The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records.

Conditions for Clearing the Message/DTC

The PCM will turn the message OFF after one run and pass of the diagnostic test.

A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.

A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

Use a scan tool to clear DTCs.

[brmurph]

Thanks for all the detail as always BBF!! I went with the section that said "Troubleshooting Hints This DTC typically indicates a malfunction within the generator. " Replacing the generator/altenator seems to have fixed the problem. Hopefuly I will get more then 13 months out of this one.

Thanks again..

[BodybyFisher]

Glad I was able to help. You might want to check for resistence in your charging system (battery cables, grounds), its very odd that your alternator did not last.. especially an AC Delco...

Have you jumped anyone?

[brmurph]

I haven't jumped anyone but I did just get a new garmin 760 Nav Unit. Love the unit but it has problems with my front power outlet as I had replaced the 20 amp fuse 3 times before I gave up and pluged the unit into one of the rear outlets (kept shorting out). It would seem that the fuse was doing its job but maybe somehow it caused the problem with the alternator??

Thanks again.

[BodybyFisher]

Not likely, because it is working in the rear and has not blown anything right? It sounds like something is wrong with your front outlet.

Unfortunately, it could be that the alternator just crapped out from heat or some unusual resistance in your system. Try to check your battery cables for resistance. Does it turn over fast, how does the starter turn? What is your charging rate? Resistance in your battery cables will cause your changing rate to be high.

It could just be that your alternator died from heat, keep in mind that they went to water cooled alternators for a reason. How is the car driven?, traffic?, temps?

[brmurph]

I just realized I never updated the solution for this problem (I was on vacation and guess I forgot when I got home). Anyway I put a another AC Delco alternator on (while on vacation :-) and that fixed the problem, no problems since.

Thanks!!

[BodybyFisher]

Glad to hear it, its a shame it was out of warranty and that you could not return it for a new one