Dash Lights on After Dead Battery

Discussion in '80-Series Tech' started by PACK MULE, Mar 22, 2013.

  1. PACK MULE

    PACK MULE

    Messages:
    170
    Got back from a business trip last night and the LX was dead in the airport lot. Key fob would not open the doors, horn would not work etc. Been having some trouble with the fob and still not sure if it is the source of the issues. Ran jumper cables off of 2nd battery and when hooked to the positive the alarm started going off. Went ahead and used the fob to lock and unlock the doors, reset the alarm and still the truck would not start. It is the factory LX alarm system.

    Went ahead and hooked up the cables again to the 2nd battery, jumped the truck and it started. Got to the house, shut the truck off and the ABS light, Seatbelt light, Park light and one heater selection light stays on. Put a charger on the battery last night, LX started up this morning but the same lights are continuing to stay on with the key pulled out of the ignition switch. I also unhooked the battery while charging to see if the ECU needed reset.

    Scan guage is showing no codes and the volts coming off according to it is 14.2 or so.

    Is this the "Christmas Tree Effect/ Bad Alternator" that I have seen on a few searches or am I chasing another problem? PO mentioned a slow battery drain but I thought the battery he had in it was no good and replaced it. Have not seen these lights on when the truck has been off until last night.

    Thanks,
    Pack Mule
  2. landcrshr

    landcrshr

    Messages:
    618
    Location:
    Bay area, Ca.
    All that I can offer is that these lights are fed from the 10A "gauge" fuse.
    If that were open, maybe they could be back-fed through some other component, like something aftermarket that also uses another (battery) circuit.
  3. flyingeagle

    flyingeagle

    Messages:
    54
    Location:
    Hawaii
    Aloha .. . I hope this helps and is not completely useless information. Verify that all fuses are getting power like they should and none are open (broken wire.) Use a amp meter or a poor mans way to check for a battery drain, disconnect the negative battery cable and clamp the alligator clip to the negative battery post, then put the other end of the meter/test light to the negative cable, does it read high amp draw/light up brighter than it should? You can check this method by turning on your headlights, you will see that the test light gets brighter or the amp draw goes up considerable. If so, I go to the alternator and disconnect it first to see if the light goes out, if it does, the diodes in the alternator are bad and causing the battery drain, the alternator will work properly but you will still have the battery drain while off. If that does not make the light go off, I head to the fuse box and start pulling fuses until the test light goes off, when it does, I have isolated the circuit that the battery drain is in and I start disconnecting everything in that circuit until I find what part is draining the battery. Hope this little bit of knowledge helps.
  4. flyingeagle

    flyingeagle

    Messages:
    54
    Location:
    Hawaii
    You can also check the down stream sides (I call the "Up Stream" side of the fuse box the side of the fuse that is being supplied power by the battery, one half dozen or the other) of the fuse by hooking your alligator clip of the test light to positive and putting the other end of the test light to the down stream side of your fuses, if your test light lights up, you know that the wire is not open to whatever part is next in the circuit. BE SURE to not apply more voltage to any part that is not rated/intended. If you want to be safe, reduce the voltage down first, use circuit breaker, then check circuits. You can also disconnect your ECM and any other parts you wish, just use a meter to check continuity between the fuse box and any parts disconnected. The most important part of this test is not FRY anything. Good Luck, I am battling numerous electrical issues on mine as well.
  5. JCruse

    JCruse

    Messages:
    819



    It sure helped me!
    I don't have a battery drain but I have in the past and wish I would have known this then. Now I just hope I can remember it for the future. :frown:









    .
  6. flyingeagle

    flyingeagle

    Messages:
    54
    Location:
    Hawaii
    JCruiser
    The poor mans way is with a test light. Do not forget that even crossed wires can draw power and the problem may not be a part. I have seen this at doors, retractable headlights & mirrors to name a few. Body Shops who pinched wires while replacing parts, even wires in a headliners or the dash where a rat has eaten through wires and caused them to touch. The way you find crossed wires is to follow the wires (this is why I like to go to the fuse box as it tells me which way to go, towards the battery or away from it,) it's tedious but the only way to find where a wire is actually broken, if that is the problem.
    I will also run long wire(s) for testing, long enough to reach around any car or truck from the battery and/or battery cable(s) as this way the light or meter is right next to where I am working and it also insures that I have the very best connection and not a poor body ground/positive connection. Make sure your alligator clips have protecting from grounding out in case you have to connect to the power side. A short you have to tackle a little differently, I use Circuit Breakers and a needle for that that's another story.
    I keep things like this in a folder for future reference, just copy and paste it on a new "Word Document."
  7. PACK MULE

    PACK MULE

    Messages:
    170
    Thanks for the tips. Going to try and sort through this today
  8. PACK MULE

    PACK MULE

    Messages:
    170
    Well we have isolated the issue down to something to do with the rear heater. Pulling the fuse on the rear heater, the 20A fuse, the lights shut off on the dash We also noticed while trouble shooting that the windows were also working with the key shut off. Inside the left kick panel the electrical diagram shows a relay for the heater and something to also do with the window power.

    Had another rig come by and switched rear heater relays and the lights continued to stay off. Checking on a parts rig to see if they are the same and we will install it if they are.
  9. flyingeagle

    flyingeagle

    Messages:
    54
    Location:
    Hawaii
    Let us know if it fixes your problem as I will put this knowledge away for future reference.

    Mahalo
  10. REKCUT

    REKCUT SILVER Star

    Messages:
    3,287
    Location:
    Springfield, Mo
    It fixed the problem. Once I looked at the dash and saw the light first hand I had a good idea that there was a relay somewhere that was staying open and bleeding back power. The lights were on with the key off but they were not on at full intensity. They were just lightly glowing. The windows would also keep working after the keys were out of the truck. When we pulled the battery cable off and then put it back on the truck returned to normal, but as soon as you turned the key on and powered everything and turned it back off the lights and window power stayed on. We next pulled fuses one at a time until the lights went out. When we pulled the gauge fuse it went away but the windows still worked and the lights came back on when you reinstalled. When we pulled the rear heater fuse the lights and windows again lost power. Went to the FSM and found the heater relay in the drive side kick panel and pulled it and replace it with one out of my truck and problem solved.

    ITs a long process chasing down each section but its the only way to track it down and it beats just throwing parts at it.
  11. lp2k

    lp2k

    Messages:
    320
    Location:
    Orlando, FL
    After I drove with a dying battery, I fried my alternator, so when I changed the battery I still had a bunch of lights on... after the alternator and battery , no more lights.

  12. PACK MULE

    PACK MULE

    Messages:
    170
    It does appear that the relay took care of the problem. Once we have a wrench day I do want to go through and check each circuit to confirm we are not getting an additional drain on the battery that is above and beyond normal.

    Figure the clock, radio and alarm have some sort of drain that will always be there. Probably some sort of milli-amp draw that will always be there.
  13. REKCUT

    REKCUT SILVER Star

    Messages:
    3,287
    Location:
    Springfield, Mo
    I think this is a different sort of lights. My understanding of a bad alt is the lights are on when the truck is running. These lights were on only when the truck was turned off and the key was out of the ignition. It was a bleed back of power through an open relay. This can come from the alt but we unplugged the power from the alt and it had no effect on the lights.
    Last edited: Mar 26, 2013

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