First I would like to say thanks for any help you can offer.

My wifes 2007 HHR had the bat light come on one morning, so I checked the batt voltage and it was only 11 volts, so I "guessed" the alternator and replaceed it.

Batt light still on and voltage still around 11 volts.

I charged the batt and load tested it, and was ok but not great so I replaced the batt, but the car still has the same issue. Replaced the fuseable link between the starter and the alternator but that was not the problem.

I am not sure how the alt works on this can or what the exciter voltage should be?
I could use some help and I would appreciate your time and effort.

Thanks
Jeff Cuppy

 

Test that replacement battery, even new ones can be low voltage, you need 12.4 volts or higher to run the onboard computer system and electronics

 

Thanks for the reply, but the batt checks over 12 volts even after setting for over 12 hours.

I would really like to know how the alternator exciter voltage is regulated.? It looks like its controlled by the ecm?

Thanks again in for the help.
Jeff

 

Go to advance/autozone/O'Reilly and have the alternator checked.

When the engine is running the voltage at the battery terminals should be upwards of 12V, that is testing the voltage output of the alternator. Engine off should be higher than 12.5V.

The exciter is controlled by the BCM the sensor is that platic ring around the negative battery cable.

 

How much over? A tenth or two can be critical.

 

A battery that drops to 12.3 V in just 12 hours is not a good battery. A battery at 12.6 after a month I would consider marginal.

 

I would consider that exceptional.

 

Check the alternator belt tension just in case - it will not be superfluous.
If during the movement (especially the start) you hear a whistle from under the hood, this is a loose alternator belt.
I understand that when replacing the alternator, the belt should have been properly tensioned, but there may be a defect in the fasteners.

 

I saved an AC Delco OEM pulled from my 2011 HHR a couple years ago, even tho it seemed to be fine. It holds 12.6 - 12.7 after three months. Couldn't bring myself to chuck it. Might cover me if one of my aftermarket batteries buys it. Haven't had it load tested but now I'm curious.

 

Hello, and again thanks for the help.

Im learning a bit on how this charging system works.

I did not know about the current sensing on the neg. batt cable (Hall Effect?). That seems to supply info to a module, using a 5 volt reference voltage?
This module apparently communicates with the engine ecm that turns the alt. on, and senses alt duty cycle?

I guess I will ohm some wires out and look for an open condition, but I doubt I find anything, and Im not sure I have any equipment. to check either module.

Im am surprised this issue is so complicated, but I hope its something simple.

Thanks again
Jeff