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Battery discharging while truck is shut down...

Discussion in 'The Garage' started by Shaggy, Feb 8, 2004.

  1. Shaggy

    Shaggy 3/4 ton status

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    I did some work on the truck yesterday, and partway through the work I noticed that the heater fan was running very slowly, while the truck was shut down. I figured that it was odd and unplugged the fan. Took the truck for a test drive at the end of the day and everything worked great. I went out to drive it again this morning and the battery was dead. DEAD dead. Like, so dead that the solenoid wouldn't click and the lights wouldn't come on at all.

    I junpstarted it and drove it around a bit, went to get gas and it wouldn't start after I had put gas in it. A friend came to jump it and I went for a 20 minuted drive to try to get the battery charged up. When I left the house the battery was reading about 11.5 volts when the truck was idling, when I got back it was 12.5, so it looks like the battery was charging on the drive.

    I doublechecked all of my work, nothing that I worked on yesterday is drawing power when the truck is shut down. If I disconnect the battery it stays at the same voltage, if I connect the battery cable I can see the voltage go down really slowly, about 3/1000 of a volt per second. If I run the truck at 2000rpm I can see the battery charging fairly fast, about .5 volts every minute. It's on an external trickle charger now to see if it will take a full charge.

    The electrical system has never given me any problems on this truck, but I know that the ignition switch is worn. Could it have finally eaten it and that'w what's causing this, or this going to be a bigger problem that will take a while lot of tracing of wires?

    Help! I really want to get out and enjoy my truck, but every time I get something fixed something else goes wrong the very next damn day!

    Sorry for the long post, I just wanted to give all the relevant info.
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    What is your voltage across the battery with the engine running and all the electrical accessories on?
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    How old is your battery? If it is anywhere near 3 years old or older buy a new one. Batteries don't last much longer than 3 years before starting to give troubles of some sort or another.
     
  4. Shaggy

    Shaggy 3/4 ton status

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    Voltage across the battery was 12.5 and rising, it wasn't fully charged. Once it is I'll turn all the accessories on and try it out.

    The battery is about 4-5 years old but really hasn't been used that much. It's an Optima so it's not like it's a cheap battery or anything. I really don't see how an old battery could make accessories run when the truck is shut down though.
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    1. Optimas are crap. You find people that swear by them but I won't sell them. They're total trash. If you got 5 years out of yours, be happy.

    Since there is no free acid inside an Optima they sulfate very quickly if ever left discharged. While this is true for all car batteries, it's worse for Optimas and other AGM batteries than any other.

    2. If you are only reading 12.5 volts across your battery with the engine running at any time, your alternator is not putting sufficient charge into your battery. At no time with the engine running should the battery show less than 13 volts.
     
  6. Shaggy

    Shaggy 3/4 ton status

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    [ QUOTE ]
    1. Optimas are crap. You find people that swear by them but I won't sell them. They're total trash. If you got 5 years out of yours, be happy.

    Since there is no free acid inside an Optima they sulfate very quickly if ever left discharged. While this is true for all car batteries, it's worse for Optimas and other AGM batteries than any other.

    2. If you are only reading 12.5 volts across your battery with the engine running at any time, your alternator is not putting sufficient charge into your battery. At no time with the engine running should the battery show less than 13 volts.

    [/ QUOTE ]

    OK, thanks for the info on all that stuff, but this does nothing to help me figure out why my accessories are getting power when they shouldn't be. My Optima has served me very well and I will likely replace it with another one when this one dies. It's never been left discharged for any length of time and in the past has held good voltage even after sitting for 6+ months.

    As for the voltage across the battery, you're saying that the battery is supposed to suddenly jump from low voltage to >13 as soon as the engine is running? I'm no electrical expert, but it seems to me that the battery was charging since the voltage was steadily increasing. Maybe I'm not getting you're teminology. My battery is connected to the truck using the side terminals, I was measuring voltage using the top terminals. Seems like that's what you were asking about though.
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    With a volt meter connected to the battery and engine off you are reading voltage that is currently in the battery, once you start the vehicle you are now reading voltage the alternator is charging at.
     
  8. Shaggy

    Shaggy 3/4 ton status

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    Interesting... I put the charger on the truck and measured the battery while it was being charged by that, it acted the same as when it was being charged by the engine. I guess that external chargers act differently or something.

    Anyone have any tips about my original problem?
     
  9. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Get your battery fully charged (12.5v).....remove the neg battery cable and attach a test light (cable on one end, neg battery terminal on other).....if the key and everything is off and the light is on you have a draw, the brighter the light, the higher the amp draw....pull out fuses one at a time, if the light goes out you've found the circuit and look deeper at those accesories.....if the light stays on with all fuses removed remove the hot wire to the alternator, sometimes it will draw amps with key off. Good luck /forums/images/graemlins/thumb.gif
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    With a volt meter connected to the battery and engine off you are reading voltage that is currently in the battery, once you start the vehicle you are now reading voltage the alternator is charging at.

    [/ QUOTE ]

    Exactly. 12.5 with engine off is fine. That is an 80% or so charged battery and is perfectly acceptable although 12.6 or more would be ideal.

    Never at any time with the engine running should it drop below 13 volts. That was the intended tech advice to be given in that post.

    Don't assume that your battery is good though. Any auto parts store can test it for you.
     
  11. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Right on, never try to diagnoise with a marginal battery. Make sure it has at least 12.5v and it load tests before continuing. With a good battery testing batt voltage with engine running should always give you 13.4v or more. However the blower motor staying on will be your next fish to fry. Good luck
     
  12. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd try a new iggy switch, the old one is probably allowing some contact where it shouldn't. They're a pain to swap out...IME anyways.

    With the batt hooked up try wiggling the key a little forward or backward and see if the fan shuts off at any point. That should confirm the problem is with the iggy switch.

    Rene
     
  13. Shaggy

    Shaggy 3/4 ton status

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    Battery is still charging, it's up to 13.6v now. Rene, the switch was my first thought, I gave it some wigglin action and it didn't affect anything. I think that that will be my first step anyways, if the charging system doesn't turn out to be fubar. Once the battery is charged all the way I'm going to take it for a spin and see if it's still reading as fully charged when I get back.

    How can I tell what my alternator is putting out, or is that what you guys are saying I'm looking at when I check the battery when the truck is running?
     
  14. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If the volt meter is anything above 13.5v but below 15.5v with the engine running your alternator is working properly.
     
  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    [ QUOTE ]
    How can I tell what my alternator is putting out, or is that what you guys are saying I'm looking at when I check the battery when the truck is running?

    [/ QUOTE ]

    With the truck not running check voltage at the battery, with the truck running check it the same way. On my truck, not running, batt 1 is 12.99 V, Batt 2 is also 12.99 V. At idle they both read 14.87 V tested the same way. If the alt wasn't working the voltage reading at idle would have been the same as when it wasn't running.

    Rene
     
  16. Shaggy

    Shaggy 3/4 ton status

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    For the record, I love my Fluke 89. /forums/images/graemlins/thumb.gif It made this SO much easier, I just bridged the negative terminal every time I tried something in order to check the amp draw. When I started it was drawing about 3.5 amps, the eject mechanism on the stereo was going nuts and the blower for the heater was spinning lazily.

    OK, so first I pulled all the fuses with no effect other than the amperage draw dropping a little bit when I pulled the fuse to the courtesy lights (expected, since the door was open and even after pulling the lightbulbs I assumed it would pull some power into the system with the doors open). I then disassembed the ENTIRE dash and unplugged every connection in it, and pulled every fuse, flasher and relay on the truck with virtually no effect. I then started under the hood, removing the grounds to everything I've added, the compressor, O2 sensor etc. Once again, no effect.

    Anyways, long story short, I noticed that the plug on the alternator for the voltage regulator looked kinda charred on the inside so I yanked it off and sure enough it looked burnt, so did the place it plugs into inside the alt itself. I checked the amp draw and it had dropped to about .2. I'm not sure what's normal, this seems high to me but nothing was running and it sure is a hell of a lot lower than it was. Maybe the carbon on the connection that burnt up was bridging between the terminals even though it wasn't plugged in anymore?

    Sorry for the long post but I'm happy right now and wanted to share my success. Any input on the remaining .2 amps of draw I have would be great (memory for stereo presets and whatnot is part of it, just seems like it would be way less). Or if I'm an idiot and I'm fooling myself that I found the problem, please let me know.
     
  17. Tweetysuarus

    Tweetysuarus 1/2 ton status

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    Well glad you solved the issue!
    Bill
     
  18. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    Mine does the same thing. I will have to try that tonight. I have been pulling the +lead everytime I park it.
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    Glad you figured that one out!

    I guess you could also eliminate in cab or outside of cab by disconnecting the firewall connector for the fuse panel and then testing draw. Easy to do, and sure fire. /forums/images/graemlins/smile.gif
     
  20. Shaggy

    Shaggy 3/4 ton status

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    [ QUOTE ]
    Glad you figured that one out!

    I guess you could also eliminate in cab or outside of cab by disconnecting the firewall connector for the fuse panel and then testing draw. Easy to do, and sure fire. /forums/images/graemlins/smile.gif

    [/ QUOTE ]

    I would have done that but my waterproofing* makes it difficult.

    *lots and lots of silicone injected around the connectors. /forums/images/graemlins/crazy.gif
     

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