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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: Barraphernalia on April 08, 2008, 09:17:53 AM
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I've been having a problem for months now. It's as if the alternator is going out. (battery is not being charged-sometimes)
I've had both the Alternator and Battery tested multiple times and they've come out good. I finally just went ahead and replaced the alternator for good measure and the problem went away for about 3 months. It's back now. I had the battery tested again and it came out bad (or so they told me, now I'm having doubts) so I replaced it. That got me a few days, but it wouldn't start this morning. It's not completely dead, but it doesn't have enough to turn over.
The cables are pretty new, but the positive is already corroded some. I thought about trying it next, unless anyone knows of another common problem I could look into.
Thanks,
Barry
85 Silverado - 350
SWB-2WD
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Check all of your ground wires, The Battery should ground to the engine and the engine should ground to the frame and the cab should have a ground to the frame as well.
It worked for me a couple years ago
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Does it die after sitting for a longer period of time? or will it happen immediately after driving?
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I have gotton brand new alternators, and battery's over the years that were no good! I have also had an alternator tested, they said it was good because it charged. Turns out it had a bad diode and it was drawing the battery down.
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What kind of electrical items do you have in the truck? All stock stuff or a BIG stereo, off road lights, seat heater/ massager?
There's several reasons a battery goes dead, alt not charging or not able to handle the added load, an accessory staying on and draining it when it sits, or to much voltage drop between componants. Your gonna have to check it with a voltmeter and a test light.
To check for a battery drain hook the test light clip to a GOOD ground and disconnect the negative cable from the battery while touching the probe of the test light to the battery neg. term. If the light lights up with the cable disconnected than you have a drain running the battery down while the truck is shut off.
With the engine running carefully check the voltage at the alt output wire with the pos. voltmeter lead and touching the neg v. meter lead to the alt housing. Should be 13.5v. to 14.5v. Now with the pos v. meter lead still on the output term. of the alt. touch the neg. v. meter lead to the positive battery terminal it should show almost no voltage. If it shows more than 1/4 to 1/2 a volt you have to much drop in the charge wire.(bad connection or overloaded wire)
Touch the pos. v. meter lead to the neg. of the battery and the neg. v. meter lead to the alt housing should be almost zero volts. If not you have drop in the neg side. (same deal)
Let us know, Matt
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Does it die after sitting for a longer period of time? or will it happen immediately after driving?
The first time it died while driving, but it's drained while driving since then (I just have seemed to make it to where I was going, only to have it not start when I was ready to leave)
What kind of electrical items do you have in the truck? All stock stuff or a BIG stereo, off road lights, seat heater/ massager?
All stock stuff, no extras.
To check for a battery drain hook the test light clip to a GOOD ground and disconnect the negative cable from the battery while touching the probe of the test light to the battery neg. term. If the light lights up with the cable disconnected than you have a drain running the battery down while the truck is shut off.
With the engine running carefully check the voltage at the alt output wire with the pos. voltmeter lead and touching the neg v. meter lead to the alt housing. Should be 13.5v. to 14.5v. Now with the pos v. meter lead still on the output term. of the alt. touch the neg. v. meter lead to the positive battery terminal it should show almost no voltage. If it shows more than 1/4 to 1/2 a volt you have to much drop in the charge wire.(bad connection or overloaded wire)
Touch the pos. v. meter lead to the neg. of the battery and the neg. v. meter lead to the alt housing should be almost zero volts. If not you have drop in the neg side. (same deal)
Let us know, Matt
Thanks a lot, I'll try all this, but It may not be until this weekend..
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It is most likely a ground problem. I'd check all of your grounds and make sure that they are nice and tight and have no corrosion or interferences (kinked wire, frayed wire, not a clean ground connection like paint or something). Other than that I wouldn't know what it would be.
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Well if it happens while driving and not sitting after a long period of time it's not a parasitic draw. You have a charging system problem. Check the connection at the alternator and make sure the connector is ok.
Do you have a gauge or idiot light?
Do you have a digital volt meter?
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Sounds like you might have an electrical draw somewhere that is causing a system drain, other than the battery or alternator... Check the cables, and grounds as suggested, but also look for other items that might be causing it(Dome light,door pins for the light, glove box light,dash light,radio,ashtray,etc...)...
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It's not a parasitic draw if it's happening while he's driving. It's a charging system issue.
A charging system full field test would test the ability of the alternator's current output and a voltage drop test will reveal if it's a resistance problem. This can be checked easily with your meter if you have one.