Delayed Charging?

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  #1  
Old 10-30-06, 06:00 AM
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Delayed Charging?

Looking to find out what could cause an alternator to delay charging after starting up - flakey regulator??

For the past few days when I start my 2003 Silverado Duramax it will run without charging for 30-45 seconds, then all of a sudden the lights brighten, the voltmeter runs up to 14 volts, and everything's ducky.... But until it starts charging, the computer will at times start giving me random false error messages - brakes need servicing, etc. After it starts charging, if I restart the engine, it will repeat the delayed charging time.

It never did this before, and the only recent thing I can think of is that 3 weeks ago my son sat in the vehicle for hours watching movies on the DVD player (the truck's loaded...) - and killed both batteries. (he didn't want to come into the trailer show with us.....) I got a jump - no issues and it recharged fine on the way home. And no - cables weren't reversed with sparks flying, etc.
 
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Old 10-30-06, 02:39 PM
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Most likely, the diode pack on the alternator is going bad, which basically means, bad alternator. It could be this, or the belt is slipping on the alternator. I dont think there is any relay between your alt and your batt. It should be a straight shot of wire, maybe a fuse in between. You can have Autozone test the alternator for free, though sometimes, these tests are not to reliable.
 
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Old 10-30-06, 04:25 PM
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I checked with a couple guys that have similar trucks - they're actually seeing the same thing - start truck, voltmeter hovers around 12V, after 30 seconds or so - up goes the voltage to 14+V.

I'm suspecting I've got a battery going bad and not staying charged - I threw a charger on the truck last night and this morning did not get any goofy errors - likely because the battery voltage was up where it should have been. The charger was working at 7-8 amps for a while, so the batteries were low.
And, while driving, the voltmeter stays pegged at 14+Volts so I'm beginning to think the alternator is OK.

I think I'll get both the batteries tested...

Thoughts?
 
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Old 10-30-06, 05:02 PM
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Those batteries were probably drained pretty good from whoever was watching those movies, etc. Also, not sure if the glow plugs stay on for a bit longer and thats why you don't got the full 14vDC until later. I would just get a multimeter and check your batteries every days or two. If after a few days, and they seem fine, your truck is probably good.
 
  #5  
Old 10-30-06, 07:59 PM
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Actually using the batteries until they are dead could be the cause of the problem. Your truck has an alternator (not a generator) which is designed to operate with properly charged batteries. Using your alternater to charge the batteries (even though its done countless times) can overload it and cause it to go bad for various reasons.

I wouldn't assume the alternator is bad just from this info, have it tested and if you end up replacing it I bet you will find a warning that comes with the new alternator to make sure your batteries are fully charged when you install it.

John
 
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Old 10-30-06, 08:51 PM
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Good advice, guys -thanks. The juice-draining movie watching was 3 weeks ago in Toronto - and a voltmeter showed them at a little over 10 volts - not drained flat, just not enough to crank the diesel. After starting, I drove for over 2 hours - I'd expect them to be back up by now..

At any rate, I'm gonna get the batteries checked first, then the alt if I need to go further - there's a rebuilder just around the corner if it needs service. Thanks a ton!
 
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Old 11-06-06, 08:46 PM
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Just closing this one off..... I pulled both batteries and had them load tested --- both failed! Tested at 770 CCA and also with a lower load test at 340 CCA. Both failed twice.

After talking to a couple seasoned dieselheads, it seems that with diesels it isn't uncommon for both batteries to end up this way. One battery gets a bit weakened, the other contributes more to compensate and ends up toasted as well. They end up being replaced in pairs... Damn!

They didn't last very long - 2003 vehicle - AC Delcos which are normally well rated. I think the warranty is up to 84 months prorated, but I'm not the original owner - might try the dealer anyway first before springing full price for 2 new ones..

Thanks for the help, though, guys!
 
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Old 11-07-06, 01:52 PM
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Glad to hear you found the problem. That sucks that you have to spend twice the money now.
 
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