: weird battery issues

03-06-07, 11:06 PM
hey guys i have a problem with my caddy. the no charge light comes on really dimly when i turn my brights on or when i turn the a/c or defrost on. also the light comes on really dimly when im rolling down my windows. if i roll my window all the way up and keep pressing down on the switch to roll it up, the light comes on pretty brightly. is this because i went to too many drive in movies? have the twilight sentinel enabled? does that really drain a lot of battery?

Cadillac Giovanni
03-06-07, 11:21 PM
I'm not sure. A "No Charge" usually indicates that the alternator itself is not delivering a charge to the battery, or simply that the battery is holding a charge poorly. Have you had trouble starting the car? That uses more battery power than anything.

I know I killed mine repeatedly by listening to the radio with the car parked. I had to have the key in the on position because the accessory position in my car doesn't work. After enough of this, the battery will lose it's ability to hold a charge well. You may want to invest in a brand spanking new one if you get the chance.

I'm not sure about the twilight sentinel either, i've never used mine...

If the car is starting okay, then the battery is holding a charge fine, but if the alternator is struggling to deliver a charge to the battery during operation, it may be getting close to time for a new one...

03-07-07, 11:33 AM
no the car is starting fine... havn't had a problem with it yet. the battery is pretty new i got it when i got the car last august. maybe i should charge it

03-07-07, 12:33 PM
no the car is starting fine... havn't had a problem with it yet. the battery is pretty new i got it when i got the car last august. maybe i should charge it

Sounds like the alternator needs to be checked out. It's either not putting out enough amps, or volts. Either one will not be able to keep ur battery charged up the way it should and eventually u will find that u won't be able to start ur car cuz the batter is dead.
When getting ur alternator checked out, make sure the battery cables are in good shape and that the connection is clean where it comes in contact with the battery itself. If the cables are in good shape, and the connections clean, then u may have a problem with a ground.
Checking for a ground would call for inspecting the ground end of the negative battery cable. It could be dirty or loose. Next one would want to inspect the body to engine ground for a good connection. There is also a voltage drop check that ur mechanic can do with a voltmeter.
New batteries can go bad too, like anything else. More than likely tho, it sounds like ur alternator. Keep us posted. Remember, look for the simple things first.

Old Fleetwood
03-07-07, 04:23 PM
Are the belts properly tight?

The Ape Man
03-07-07, 08:11 PM
You probably have 1 or more bad diodes in the alternator. It will make rated voltage but won't be able to deliver rated current in that condition. Everything will seem OK until you start turning on things which draw heavy current. A rainy day with the defrogger, wipers and blower will show the thing up. Another hint is a whining on the stereo that changes with engine speed. If the stereo was clean before and now has some alternator whine then listen to it. Alternators whine when they need help.
They sing when they work properly.

03-08-07, 12:37 AM
It's either not putting out enough amps, or volts. Either one will not be able to keep ur battery charged up the way it should and eventually u will find that u won't be able to start ur car cuz the batter is dead.

A rainy day with the defrogger, wipers and blower will show the thing up.

This thread is a festival of typographical errors. At any rate this does sound like an alternator problem. It's probably not doing much; I've had cars with good batteries have the alternator die completely and the "Charge" light come on only when you use something electrical.

Edit: Oh yeah -it could be the regulator, too. I don't know where that is on that car though, on some cars it's integral to the alternator.

Old Fleetwood
03-08-07, 01:54 PM
Hey, Red -
Those aren't Typos!:tisk:

The BATTER was missing and that was really a problem, because
DEFROGGER didn't work and the whole damn car was getting full of croakers! :thumbsup:

03-08-07, 08:13 PM
so im guessing its the alternator... ill take it down to autozone and have them test it. how much do new ones cost? like what $100 or something?

Old Fleetwood
03-08-07, 09:56 PM
Hokay - - -
Down at your fiendly AutoZone store, here's what you get for your 85 FWB's alternator IF THAT'S THE PROBLEM ( ! ).
> DuraLast 100 amp, Limited Lifetime Warranty, $78.49 +tax
> ValuCraft 100 amp 1 year Warranty, $74.99 +Tax
They don't show a core charge so I don't know if you have to give your old one back to them.
Happy wrenching. :thumbsup:

03-09-07, 12:07 AM
You can get a 140 amp alternator out of a 90-91 Deville without heated from glass at Autozone for $100 and a $75 core. It can be fairly easily adapted to the older engines (new connector for it and the older pulley).

03-09-07, 01:32 PM
If this is a 4100 engine check the smog pump belt. Make sure its not loose, worn out. If the smog pump belt slips, the alternator will discharge when trying to recharge the battery. To confirm if the smog pump belt is too loose, try to rotate the alternator pulley the opposite direction of normal rotation with you hand, ENGINE OFF! If you can rotate the alternator pulley, the smog pump belt is loose, glazed or worn out. must be re tightened from under the car! This is correct for any 4100 engine with multiple belts.

03-10-07, 02:25 AM
okay thanks for the help guys! ive been pretty busy and havn't really gotten time to take a look at it so tomorrow will be the day. ill keep you posted

The Ape Man
03-10-07, 09:17 AM
Dunno exactly how they check alternators at awful parts stores. If the test does not load the alternator to the amount of current that the application (car) presents, it's incomplete. The test would also have to include at least 5 minutes continuous load at at least 1/3 rated current output. I've heard a few horror stories about how people had the alternator bench tested by the parts store (usually after buying a new one, installing it with a stone dead battery then killing the new alternator by charging the dead battery) only to be told it was OK. So now we have R&Red the alternator 3 times and we still have a problem. NASA rocket scientists all work at auto parts stores part time on weekends.

03-10-07, 04:29 PM
Not ALL parts guys are full-time NASA engineers:tisk:

Personally, I drink beer on the weekends and sell parts and equipment through the week:alchi:

Definately the alternator, as the others have said. The output is easy enough to check with a multimeter. Red lead to the primary on the alt and black to the battery ground terminal. Anything less-than 14-volts with engine running, lights on, heater blowing, blah-blah-blah indicates a weak alternator on a GM. Usually it's internal regulator is the culprit.

If you go to Auto Zone or Advance, look for the guy/gal with the MOST gray hair as they will probably have the most knowledge under thier belt. I'm a sales rep for CarQuest and have gray hair too. When the alt in my '83 Coupe DeVille started acting up I just warranteed the damned thing:bigroll: It helps to know your partz guy...

The Ape Man
03-10-07, 09:42 PM
Dude, you can't simply check the output of an alternator with a multimeter and call it OK. It isn't that easy.

03-11-07, 09:14 AM
Actually, that multitester procedure is extremely accurate if performed correctly. An electrical engineer showed me how and saved me from several alternator purchases over the years.

Do YOU work for NASA?

The Ape Man
03-11-07, 09:24 AM
Ok. Let's hear this extremely accurate engineered proceedure step by step please.

03-11-07, 09:39 AM
Re-read my first post in this thread. If one can make toast, one can check thier alternator with a multimeter.

With the meter set in the DC-volt range, 20 is good, red lead on the primary teminal at the alt and the black lead on the negative battery terminal the meter will show you what the alt is generating at any RPM. Any great fluctuation through differing RPMs would indicate a faulty regulator.

Oh, keep yer leads and fingers away from them belts!

The Ape Man
03-11-07, 10:34 AM
That's an incomplete way of testing an alternator. Many defective alternators will still put out full voltage throughout the RPM range. Consider an alternator with 1 shorted rectifier diode. It will seem fine electrically until a load is placed on the output. Your extremely accurate engineered proceedure makes no mention of simulating a load on the unit under test. There's more inside an alternator than a regulator. Now consider another alternator with a set of brushes so short that they are just starting to fail. Your proceedure makes no mention of testing over a period of time. Most brush failures show up as intermittants initially. A voltage test done quickly (since it's so easy) could very well miss that failure also. How about an alternator with a bad regulator that applies field current without the unit spinning? Your test will miss that one totally. The alternator will discharge the battery overnight every time. One more. Consider an alternator with an intermittant short in the stator winding. Testing it cold might miss the short altogether as it only happens when the alternator is at operating temperature.
My experience with electrical engineers is they mostly fumble badly when stepping outside their day to day square. See it all the time.

03-11-07, 11:14 AM
The oddest alternator failure I had was a bad Diode Bridge. The diode SHORTED, so it put battery power back into the car once the car was shut off. And power was down (probably by 50%). Once I got in and put in a new bridge, all was fine. Oh, and when it was shut off and left alone, the alternator stayed warm....

Common failures are diode trio, brushes and regulator. Rotor and field windings are unusual failures.

Remember, the charge light is connected to the battery through the ignition switch, and then to the alternator to flash the field. So it is telling you that there isn't enough current being generated. If it is just old, probably brushes.

Autozone does free load testing in the car.

A slipping belt can do it too. Oh, a backwoods check to see if the alternator is working, is stick a wrench on the center of the rear bearing on the back of the case. If the alternator is energized, the wrench will stick to the back pretty hard. If not, the field hasn't flashed or isn't flashed with enough power.

03-11-07, 04:41 PM
I'm not trying to argue with you ApeMan but now we've gone from a simple and accurate on the car test to a total alternator workbench dissection.

I know that there are hundreds of other factors inside an alternator, however I was simply offering a troubleshooting suggestion as we all were. No harm, no foul.

One thing though. My mentioned electrical engineer never worked within the confines of a square and he rarely if ever fumbled. Working around primarily 440-volts, there isn't much room for fumbling is there. I'm looking forward to our next 18-holes of golf. One of these days I'll beat my retired electrical engineer Dad at his game, I might just have to put a couple extra beers in his cooler for insurance!:)

The Ape Man
03-11-07, 05:26 PM
Funny, all the engineers I know design stuff. The technicians actually work on it. So your dad has a B.S.E.E. or better and was working around 440 volts??? Strange situation indeed. Golf is a lot safer.
The person who started this thread needs to know how to fix his car. You suggested that an alternator can be accurately checked with a multimeter. No argument is even possible there. It just isn't close to correct.

03-12-07, 10:02 AM
If you have a carbon pile or other high current/low resistance load and a shunt, yes, you can check some of the alt with a DMM. You really need that and an oscilloscope to really know what is going on. A FSM with a schematic of the internals of the alt is quite helfful too

The Ape Man
03-12-07, 05:19 PM
A scope is always nice but a competent mechanic will know what's going on with just the other test equipment which you mention.

03-16-07, 09:30 PM
hey guys, just an update on my situation. i took my car to auto zone today and got the most grey haired guy in the place to come out and help me. turns out hes been a mechanic for 20 some odd years and knew what he was talking about. he tested the alternator, battery, and starter and didn't find a problem with anything. would having the lights off as opposed to on affect a test? im not sure if my problem happens only when the headlights are on, but i can't see the no charge light during the day time when the lights are off. is this still an issue? or is my car just misbehaving?