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Thread: Grid Heater Stuck On

  1. Top Of Page | #1
    Gump's Avatar

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    Grid Heater Stuck On

    I noticed a few times now my voltage is below 12V while idling, and once my batteries were too dead to fire the truck. When it is happening the voltage will stay low even when the engine and ambient temps are warm. I unplugged the relay on the passenger side battery box which I believe sends power to the grid heater solenoid. Immediately my voltage jumped from 11.9 to 12.7. I’m guessing the solenoid is stuck on and need replaced. Tried a different relay which didn’t help. Am I on the right track? What else could that relay control?

    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

  2. Top Of Page | #2
    I WILL STAND! AK Bob's Avatar

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    Grid Heater Stuck On

    Quote Originally Posted by Gump View Post
    I noticed a few times now my voltage is below 12V while idling, and once my batteries were too dead to fire the truck. When it is happening the voltage will stay low even when the engine and ambient temps are warm. I unplugged the relay on the passenger side battery box which I believe sends power to the grid heater solenoid. Immediately my voltage jumped from 11.9 to 12.7. I’m guessing the solenoid is stuck on and need replaced. Tried a different relay which didn’t help. Am I on the right track? What else could that relay control?
    Yes, sounds like your grid heater solenoid is stuck closed and needs to be replaced. You could remove one or both of the smaller signal wires C3 & C4 on the relay/solenoid just to confirm that it’s not being commanded closed by the PCM. If the solenoid is stuck closed then remove and insulate the power wire C1 from the solenoid until you get a replacement. You should also do the wiggle check on the grid heater connection bolt (killer bolt) on the intake manifold.


    2014 RAM 3500 (Aisin) 3.73 4X4 Limited Crew Cab Long Bed DRW. Oil Bypass Filter, Fuel Filtration Kit and 50 Gallon auxiliary fuel tank.

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    2014 RAM 3500 (Aisin) 3.73 4X4 Limited Crew Cab Long Bed DRW. Oil Bypass Filter, Fuel Filtration Kit, Cold Air Intake, City Diesel Actuator and 50 Gallon Aux Fuel Tank.

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  4. Top Of Page | #3
    TexNeck's Avatar

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    Grid Heater Stuck On

    Depending where you live unhook it and be done with it.

    The truck will start in cold weather without issue as long as the batteries are in decent shape.

    2013 Ram 2500
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  5. Top Of Page | #4
    Gump's Avatar

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    Re: Grid Heater Stuck On

    I unhooked the whole solenoid and it starts charging again.

    I think my batteries are toast now.

    When it drops back to idle the voltage drops rapidly from 12.5 to 11.9.

    At a high idle the voltage is around 13.8.

    It also is giving me a grid heater code, high alternator output and intermittent ecm/pcm signal.

    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

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  7. Top Of Page | #5
    Gump's Avatar

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    Re: Grid Heater Stuck On

    In Montana, so I definitely need it.

    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

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  9. Top Of Page | #6
    I WILL STAND! AK Bob's Avatar

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    Re: Grid Heater Stuck On

    Quote Originally Posted by Gump View Post
    I unhooked the whole solenoid and it starts charging again.

    I think my batteries are toast now.

    When it drops back to idle the voltage drops rapidly from 12.5 to 11.9.

    At a high idle the voltage is around 13.8.

    It also is giving me a grid heater code, high alternator output and intermittent ecm/pcm signal.
    I would load test both batteries.

    The grid heater code (P2609) is typical with the grid heater disconnected and can be cleared once you reconnect it.

    Is your grid heater solenoid still closed with the signal wires disconnected?


    2014 RAM 3500 (Aisin) 3.73 4X4 Limited Crew Cab Long Bed DRW. Oil Bypass Filter, Fuel Filtration Kit and 50 Gallon auxiliary fuel tank.

    Sent from my iPad using Tapatalk

    2014 RAM 3500 (Aisin) 3.73 4X4 Limited Crew Cab Long Bed DRW. Oil Bypass Filter, Fuel Filtration Kit, Cold Air Intake, City Diesel Actuator and 50 Gallon Aux Fuel Tank.

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  11. Top Of Page | #7
    Gump's Avatar

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    Re: Grid Heater Stuck On

    Not sure.

    When I disconnected the feed wire the whole plastic housing shattered.

    I’ll have to just put a new one on, then try to diagnose any further power drainage.

    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

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  13. Top Of Page | #8
    Gump's Avatar

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    Re: Grid Heater Stuck On

    Took the truck on a 500 mile trip today. ECM voltage held at ~14.2 anytime it wasn’t at idle.

    When I got home parked in the driveway I let it idle for a few minutes, and the voltage slowly drops from 12.9 down to 12.4 before I shut it off.

    Going to load test the batteries tomorrow when back at work.

    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

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  15. Top Of Page | #9
    Gump's Avatar

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    Re: Grid Heater Stuck On

    New solenoid on today, same problems.

    Is this relay for the grid heater?

    It’s on the passenger battery box.

    Whenever I unplug it the voltage shoots up.

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    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

  16. Top Of Page | #10
    Gump's Avatar

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    Re: Grid Heater Stuck On

    It keeps giving me this no matter what I do, and my remote start won’t function right.

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    2010 2500 Laramie auto, deleted, DRD MM3
    1970 Plymouth Duster drag car

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