low voltage readimg
 

I have a 95 SE with the series 2 engine. My problem is my battery gauge reading. When I first start up, gauge is slow to move up. Gauge is rarely at 14 volts. It is at around 12 or a tad lower while I'm driving. At idle the gauge fluxates back and forth between-12 and around 10 many times. Also at idle at night time sometimes my lights will dim and gauge will drop halfway below to around 8 volts for about 5 seconds, then go back to around 10-12. MY mechanic said some wires to altenator were bad, didn't fix problem. My friends mechanic said postive battery cable was bad, also didn't fix problem. I got a technical service bulletin from alldata.com, it said 96 and up bonnies with my problem was a normal occurance for the car. yeah right. I took the bonnie to a electrical specia;ist, he said altenator was bad. I never heard of an altenator still working for over 6 months while being no good, but I let him replace it. Didn't solve problem. Has anyone has had or heard of this problem? Also I changed my battery from a Diehard Gold to one from parts america I think maybe close to when all this started. I know the Diehard had way more amps than my present battery, but could that be my problem? Could the battery be to weak or something else. GM may say its a normal electrical occurance but I know thats hogwash, maybe cars from the 20's and 30's but mordern cars?
Any help would be apprecited, I don't know what else to do. Supposedy all the grounds were checked as was the generator.
thanx

have you considered taking the vehicle to a local auto zone and utilizing their free charging system test? most times they will be able to give you a general idea as to where the problem is, so you dont have to guess as much.

Have you considered checking the actual battery terminals for voltage? It is possible that the gauge or voltage supplied to the gauge may be inaccurate. This can be done by simply using a multimeter set to volts and connecting to the battery. Then have someone start the car and watch the readings. Once you are sure the problem does exist then I would continue on.

You said the battery cables were replaced or other cables were replaced?

Meanwhile you know the alternator and battery were changed. It would be a good idea for you to pull apart and clean all the battery cables at both ends youself. That way you know it is being done at all connections.

As mentioned above Autozone/Advance auto can usually assist for free with a test. However it seems that something might be pulling the power down drastically. Are any of the toys and gadgets on the car malfunctioning?

Doo all of the above mentioned first... Check everything...

Onto the other things...

First these alternators will be low when you start the car.... Gage should show 12v and after several seconds once the PCM applies the powert field to the alternator the voltage will come up to 14v... If it stays at 12v you have a problem...

With these alternators it is normal to have so low periods, say 12v, but it shouldn't lase more than a few seconds at a time, and at that point the Voltage should return to 13-14v...

For a batter to be fully charged it should be at 12.6 volts, thats not always the case, but that the area it should be in... All of the electronics in the car are dependent on 12v... The system will run off 11v, but not all that well.. when you drop to 8-9v you are sucking the juice out of the battery and the alternator is not keeping up...

If you have fixed everything, and you find you need another alternator, make sure that the battery is fully charged, before you attempt to use the new alternator, you will ruin an alternator in a hurry trying to recharge a battery that is low or almost dead...

Whit all of the accessories on, you should be able to maintain a voltage above 12v..

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Thanx for the help but....
did all that. Had advance check charging system twice, everthing fine before new altenator installed and once after. I don't have any accesories running to way down system. Battery posts and cables are clean. I can't afford to keep going from mechanic to mechanic to solve this problem. I know GM issued service bulletin for this exact problem. I worked as a car salesman for a few years and I know how Gm's service works. When they can't figure whats wrong a car, and they have multiple complaints they just say its normal for the car to be doing it. It ain't normal. If I can't get this fix I'm dumping the car. It sounds like there is nothing more I can do. Thanx for tryin though. I appreciate it. If anybody has more ideas please let me know.

Someone may have to chime in here...

I believe that the red wire on the back of the alternator( red wire ) is a hot wire from the PCM... the PCM sends the power signal to the alternator to activate the power field... If its not getting full power, the alternator may not make full power...

Someone knows what the system is supposed to do and how to test it, I just have no idea who that person was as its been a very long time..

I have a 95 SE, but I have never had those issues...


Just went out side and checked for you...

The Red wire in the alternator pigtail is the hot wire, I probed the hot wire with a digital multimeter with the 20V DC setting... with the ignition on engine off I get 0v, once I start the car I get 10.20v at the red wire... This signal or voltage is directly controled by the PCM...

After I shut the car and plug the connector back in and restart I get 12.20v at the battery and then the PCM throws the voltage and the charges goes to 14.40v

If you test your car and find that you are not getting the voltage you should at that wire, then I'd say bad wire or PCM... If you have the voltage at the wire, then bad alternator, or bad connection somewhere...


And I'll say this again, low points like you have is not normal...

But low periods of 12v for a brief time is normal... as long as its a very short time and the voltage comes back quickly...

Where are you located BTW?

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jr's 3800, you're right on the money with the description of operation in reference to battery, alternator & PCM. I would try isolating some loads by removing fuses that are not vital to engine operation to see if you can get that voltage boosted to nominal voltage. Something is obviously placing heavy electrical load on the system. If you can get a hold of a DC clamp on ammeter to see how much load is on the alterrnator, that would help some. You may have a grounded component dropping voltage to ground (that shouldn't be) with ign. on & engine running. That's where the load isolation process comes into play.

Hey,
thanx again. I talked to the kid who pumps my gas (I live in New Jersey so I don't have to pump my own, we're not allowed, $3.15 a gallon if anyone is wondering!) he told me to try asking this guy who owns a local auto parts store thats been around since the 50's. He gave me the owners name and his son who now runs it. I forget about it, I'm used to the new modern stores. Anyway, Im going to print out what you guys suggest to try and show these auto store guys. I'll ask them who to recommend to see who to fix my Bonnie, the old timer has to know somebody good at electronics. Those guys in the real auto parts stores always know everythinganyway. I'll let ya know how I make out. I hope I can get it fixed, I really like my car, I don't wanna sell it. I found another 95 SSE for $2300 but it has 154k on it, mine has only around 124k. We'll see.
Thanx again so much, I really appreciate it....

Its almost a miracle!! The old fella said to take to the local GM dealer and told me who to have look at it there. I explained the problem to the service manager, he seemed knowlegable, and suggested all I could do was let his electrical guy look at for $85 bucks an hour and see what he finds if anything. He said hes never seen any bonneville or Olds 88 or Lesabre 3800 have this problem. Anyway, the mechanic spent almost 2 and half hours under the Bonnie's hood and dash. He didn't find any problems but he said he cleaned up a lot of connections and made some adjustments and tightening. He basically said as long as the car starts all the time, which it always has, and doesn't stall out, not too worry about and just keep driving. He said my bonnie was in great shape otherwise and told me to keep it. The car now: gauge shows a little below 14 volts all the time, doesn't dim lights at night anymore, still flickers sometimes but thats it. He said to live with it, its a GM and he laughed! No, really he said its cool so Im not gonna worry about it. All is well between me and my Bonnie and again.
Thanx again for all your help.......

Although not perfect, I'm glad to hear you have some resolution to the deal. Keep the bonnie. :)