bg35765 Posted January 24, 2011 Report Share Posted January 24, 2011 1994 CS Vert with 108,000 miles. LQ1. I replaced the alternator with another one from another 94 Cutlass in November of 2009. It took me about 6 hours with lots of breaks, double-checking pictures from this website, etc. Of course now I regret putting in a used alternator, but at the time I was scared I would bend something in the process of lowering the cradle and it would never drive straight again. Anyway, that alternator worked great until a week ago. Now when I am driving and have the accelerator down (1500 - 3000 rpm) the battery meter is showing that it is around the 10 volt mark. If I come to a stop light it looks like it is charging. It will usually be just beyond the 12 volt mark. I have noticed that if I am at a stop light and the turn signal is on I can actually see the volt needle move as the turn signal turns on and off. It moves between 11.5 and 12.0 volts or so. I have already bought another alternator and was going to install it this weekend, but decided to hold off because the temperature here was in the single digits. Now I'm second guessing myself. Wouldn't you expect the opposite behavior from a failing alternator? (Draining while sitting in traffic, but charging while driving.) Could it be a worn belt is slipping at higher RPMs, but works OK at idle? Or have any of you seen failed alternator symptoms like this before? Thanks! Quote Link to comment Share on other sites More sharing options...
Schurkey Posted January 24, 2011 Report Share Posted January 24, 2011 START your diagnosis by FULLY CHARGING the battery. With no load, a fully-charged battery will show 12.6--12.7 volts. More than that is just surface charge that will dissipate on it's own given some time. By all means, check the altenator belt tension, and belt condition. A belt slipping on the pulley can cause poor charging at low engine speed--and worse charging at higher speed. Perhaps the tensioner or the belt itself is toast. From there...a PROPER starting/charging power team test is in order. Should be less than one hour's labor at virtually any auto repair shop--even the likes of Sears should be able to handle this. The problem with doing this as a D-I-Y project is that you'd need an ammeter capable of ~350 amps; and a carbon pile of similar amperage capacity for testing the battery 'n' starter; and an oscilloscope or a voltmeter with a "ripple" setting for alternator testing. Not common tools for most of us. An inductive ammeter can be had from most auto parts stores; perhaps $20--but not all that accurate in my experience. If you want to take risks, you can throw parts at it and hope for the best. Not my first choice. Quote Link to comment Share on other sites More sharing options...
slick Posted January 27, 2011 Report Share Posted January 27, 2011 I was gonna ask, how is your battery? Quote Link to comment Share on other sites More sharing options...
bg35765 Posted January 27, 2011 Author Report Share Posted January 27, 2011 The battery is less than 1 year old. Duralast from Autozone -- the red top one (mid-grade), not Duralast Gold. I do have an update on this. I tried to start the car, it started for about 2 seconds and then died abruptly. Then it would not even try to turn over. I disconnected the power wire to my amplifier from the battery and then used a battery charger to jump start it. It started and the dash volt meter read around 14 volts. That was idling, so I got in and drove it around for a few minutes and it stayed at 14 volts the whole time. So I don't know. Something must be wrong with the car stereo amplifier wiring, but I am not sure what could cause that. A nicked power cable that is grounding out? Or maybe the alternator just can't handle running the amplifier. (350 watts RMS) But if that was the case I would think turning off the radio while driving would have caused the alternator to charge again, but that did not happen. For now I am leaving the amp disconnected. I have not driven the car anywhere yet, but will try to do that this weekend. Quote Link to comment Share on other sites More sharing options...
Psych0matt Posted January 27, 2011 Report Share Posted January 27, 2011 is your amp maybe not turning off like it's supposed to? Either that or is it grounding out? Quote Link to comment Share on other sites More sharing options...
BXX Posted January 27, 2011 Report Share Posted January 27, 2011 START your diagnosis by FULLY CHARGING the battery. With no load, a fully-charged battery will show 12.6--12.7 volts. More than that is just surface charge that will dissipate on it's own given some time. By all means, check the altenator belt tension, and belt condition. A belt slipping on the pulley can cause poor charging at low engine speed--and worse charging at higher speed. Perhaps the tensioner or the belt itself is toast. From there...a PROPER starting/charging power team test is in order. Should be less than one hour's labor at virtually any auto repair shop--even the likes of Sears should be able to handle this. The problem with doing this as a D-I-Y project is that you'd need an ammeter capable of ~350 amps; and a carbon pile of similar amperage capacity for testing the battery 'n' starter; and an oscilloscope or a voltmeter with a "ripple" setting for alternator testing. Not common tools for most of us. An inductive ammeter can be had from most auto parts stores; perhaps $20--but not all that accurate in my experience. If you want to take risks, you can throw parts at it and hope for the best. Not my first choice. You know they have much more advanced equipment these days to handle charging/starting diagnostics:lol: Lord I havent seen a shop with a carbon pile in a while.. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted January 27, 2011 Report Share Posted January 27, 2011 (edited) Yeah, there's electronic battery testers that play Van Halen at the battery until it submits...and then the machine prints out a "virtual load test result". I still haven't seen an electronic gizmo that can load test an alternator, though. Voltage test...sure. Ripple test...sure. Parasitic drain...sure. LOAD test...not so much. The new machines are tons faster; and they come with trilingual instructions. Doesn't make them BETTER, though. Just less likely to cause damage in the hands of a moron. I'm perfectly happy with my ancient Snap-On AVR complete with the archaic carbon pile. I don't need to assume that a capacitance/inductance/resistance test, filtered by a microchip through some algorithm actually correlates to a certain Cold Cranking Amps rating. My equipment provides a REAL WORLD test--I am actually loading the system during a load test. The overall point I was trying to make was that the alternator 'n' regulator, battery, starter, and the wiring that connects 'em all makes up a team, and a failure in one item can produce a cascade of faults or apparent faults with the other components. Sometimes it's not enough to fix ONE problem after a failure...because the defective alternator has caused the battery to fail. Or a defective starter is pulling so much current from the battery that the wiring overheated, and partially melted the battery posts. The ONLY way to properly diagnose this stuff is to test EVERYTHING; and that requires serious tools. Edited January 27, 2011 by Schurkey Quote Link to comment Share on other sites More sharing options...
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