Symptoms of a malfunctioning fuse block?

Discussion in 'Audio + Electronics' started by MIKE BROGDON, May 23, 2020 at 11:50 PM.

  1. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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    As always, thank you in advance for any and all help and information. My truck is a 1994 K1500. The fuse block clips into the bottom of the dash just above the emergency brake.

    The short version: Im getting unwanted power from my courtesy circuit. With the courtesy fuse installed into the fuse block, I am getting 12 Volts to my windshield wiper motor, and to my power windows with the key out of the ignition. When I pull the courtesy fuse out, the unwanted power goes away and the two components work as they normally should. Could this be a bad fuse block? Can I test this by removing the fuse block from the truck and place it on the bench, apply 12 Volts to the courtesy pin, and see if I have volts at the windshield wiper pin and the power window circuit breaker pin?


    The more detailed version: Since I have had the truck, Ive had issues with a power drain. With the key out of the ignition I can turn on my windshield wipers and roll the power windows down. I found that by removing the courtesy fuse, everything works normally as it should. When the fuse is installed, I have power to these two componets. I drove the truck for a few years and just left the courtesy fuse out, but I currently have the steering column out of the truck and with the extra room underneath the dash, I wanted to get this little bug marked off of my list of things that need to be fixed.

    So far I have chased the courtesy wires from one side of the truck to the other. I have not found any obvious splices or boogered up connectors. I also have not been able to find any areas where the power window circuit or wiper circuit is tapped into the courtesy circuit. With the courtesy fuse installed, I have 12 volts at the pink power window wire coming from the front of the conveince center that is mounted on the inside of the firewall just to the left of the brake pedal that goes directly to the power window switch. With the courtesy fuse removed, the power goes away at the conveience center. This meant that my issue is between this conveience box and battery. According to the power distribtion diagrams the window circuit in a nutshell looks like this:

    Battery-----Junction box on passenger side of firewall-------fuse box--------convenience center---------

    I pulled the convience center from the firewall, and I did not see my courtesy wire tapped into the pin for the power window on the backside of the box. I also did not see any jumped wires going from one pin to another that would supply power from any other circuit. I then moved back to the fuse box.

    (FUSE BOX) With my probe in the power window fuse hole, I am getting 12 volts constant. With the probe still in place, I remove the courtesy fuse and the voltage goes away. The same goes with my windshield wiper fuse hole. I pull the courtesy fuse and the voltage goes away.

    I can roll the windows up and down, but obviously with the column out I cant activate the wipers, however I probed the power wire going into the wiper motor and it is the same, 12 volts with the courtesy fuse in, no volts with fuse out.

    So, is it likely or possible that the fuse box is malfunctioning, and allowing the courtesy circuit of the fuse block to power other areas of the fuse block when they should not have power?

    I greatly appriciate any help in this. This has been a very frusterating issue.

    Thanks, Mike.

    Ill post some of the diagrams I have been looking at.
     
  2. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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  3. AK49BWL

    AK49BWL GMT400 Forever!

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    That is a rather odd issue. I just have to ask... With the fuse in or out, do the dome lights work? Cig lighter outlet? What kind of stereo is in it, and does it work? What this sounds like is a crossed wire at the radio, hot to ignition. I'd look there to begin with. This doesn't sound like a fuse box issue, but voltage on the wrong side of another circuit entirely due to a crossed line elsewhere.

    Radio: Hot to ctsy fuse to radio...

    Radio ignition: Hot to ignition switch to Wipers, Windows, Radio ignition fuses. So the radio is what I'm thinking is the culprit.

    Also, when the key is on, do the dome lights work WITHOUT the ctsy fuse?

    Check these out, follow the lines...

    https://www.ak49bwl.com/other/wires/1994K1500/PowerDistribution-1.pdf

    https://www.ak49bwl.com/other/wires/1994K1500/PowerDistribution-2.pdf
     
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  4. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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    AK49BWL, with the fuse in the dome lights work, the cigarette lighter is removed, and I could never find the wires for it.

    As far as the radio, it's original one is removed and a really old JVC is in the middle of the dash. It did work before I took it out when I began trying to find this extra power. The area near the radio is pretty hacked up. The only thing I saw was the radio power (yellow) was connected to an orange ctsy wire (hell that may be the cigarette wire) so I had to manually turn the radio on and off with the key out of the ignition.

    With the ctsy fuse out, the radio would turn on and off with the ignition, but would loose its memory. You know, what you said makes complete since. I am definitely going to go check that. That seems much more likey than a bad fuse block
     
  5. AK49BWL

    AK49BWL GMT400 Forever!

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    There's your problem :D The memory battery supply should come from the ctsy fuse, ignition from the radio fuse. These two should not be crossed lol. Probably the reason for the battery drainage as well - radios like to use up power.
     
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  6. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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    Checking now
     
  7. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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    So, I should see an Orange wire spliced into the radio fuse wire near the cd player harness? ( which is powered on when key is turned?)
     
  8. AK49BWL

    AK49BWL GMT400 Forever!

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    The ignition wire should be yellow, coming directly from the radio fuse and going to the pin directly next to the orange wire ... well if the original radio harness connector isn't there that won't be any help, but the ignition line should be yellow. Hot at all times should be orange.

    There is a second yellow wire in the harness, that one goes to the left rear speaker tho.
     
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  9. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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    You. Are. A. Freaking. Genius. Dude. So I pulled the wires down through the dash and they looked worse than I thought they did. All i did was unplug the factory harness that had a plug at one end, and had the butt splices that went to the aftermarket CD player on the other, just to try everything all at once and Boom! Ctsy fuse in, no power to windows or wiper motor. Im fixing to upload some pics. Thank you so much sir. If you are ever in the Panama City area hit me up, I owe you night of cold ones, strippers, or whatever your poision is. I have to follow up on another thread from a few years ago that dealt with this issue, I will put the fix in there and make sure to give your a shout out.
     
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  10. MIKE BROGDON

    MIKE BROGDON OBS Enthusiast

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