spiderw31 Posted January 17, 2008 Report Share Posted January 17, 2008 Ok, so I know the signs of a failed alternator. I also know that running ALL the accessories at once presents a substantial load on the electrical system, especially when idling in gear. That being said, I'm wondering if the behavior my car today is normal, or if I should be getting ready for a 3.4TDC alternator job. With lights, stereo, wipers, defog (fan on speed 2), and rear defog on, the blinkers slowed noticably when stopped at traffic lights, and the voltage needle would drop a bit below 13. As soon as the RPMs increased, the needle would go back to where it was before (just above the line past 13). Also, I noticed that after several miles of stop and go traffic, the needle slowly drifted a little below the line past 13. After returning to a higher speed, the needle slowly crept back above the line over the course of a few miles. Based on that description, does it sound like I might need an alternator soon? I don't THINK it is going bad, as I've had a couple cars that behaved like this for years without needing an alternator, but I'm just not familiar with the W platform... Quote Link to comment Share on other sites More sharing options...
Hairdo12 Posted January 18, 2008 Report Share Posted January 18, 2008 You're pulling a ton of amps, say you have 60w head lights, thats 10 amps (for both) plus 5 for the tail lights, wipers probably pull at least 7, blower is probably another 7, rear defog another 7, lets say 15 amps to run the computer and everything to run the engine. Turn the blinkers on and thats probably another 5 amps. So lets say 56 amps of draw on an alt with a max output of 105 amps and probably 60 amps at idle. Sounds normal to me, you'll be fine if you don't strain it like you're doing. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 18, 2008 Author Report Share Posted January 18, 2008 ...you'll be fine if you don't strain it like you're doing. That's the joy of driving in a snow storm What you're saying makes sense though. I know the load was high, I just wasn't sure what the alt is rated to put out (let along idle ratings). Quote Link to comment Share on other sites More sharing options...
CutSupreme93 Posted January 18, 2008 Report Share Posted January 18, 2008 mine did what your describing before it went out. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 18, 2008 Author Report Share Posted January 18, 2008 mine did what your describing before it went out. As noted though, it did have quite a load on it when this was happening... I dunno... I guess I'll have to just wait and see. AFAIK though, it is still the original alt! Quote Link to comment Share on other sites More sharing options...
ns87 Posted January 18, 2008 Report Share Posted January 18, 2008 My voltage has been dipping below 13 for a year or two at a stop light with all that junk on. I try to keep the radio and rear defogger off when I'm driving at night in the winter. Our Cutlass tail lights have 2 bulbs per side, plus 2 third brake light bulbs, plus the rear side markers, plus front indicator lights, plus headlights, plus maybe fog lights? It's quite the load for our wimpy alternators Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 18, 2008 Author Report Share Posted January 18, 2008 I try to keep the radio and rear defogger off when I'm driving at night in the winter. Hehe... once I get a real stereo in there I guess I'll really be puttin' a hurtin' on that alternator! At least yours is easy to change though! Quote Link to comment Share on other sites More sharing options...
ns87 Posted January 18, 2008 Report Share Posted January 18, 2008 true! Mine has been on for 30k miles, so I'm sure it will die again soon Quote Link to comment Share on other sites More sharing options...
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