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No power to dash!! hELP

Discussion in 'Tech Discussion' started by Marcos, Dec 24, 2018.

  1. Marcos

    Marcos Junior Member

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    A few weeks ago I went to put in a new battery in my 1980 gmc jimmy. Being in a rush I hooked up the cables backwards by mistake and lost all power to vehicle. Since then I have done the following:

    -Replaced both fusible links at junction block which were fried

    -replaced fusible links down at starter

    -replaced ignition switch

    //since the replacement of the links and switch my Jimmy now starts however I don’t have power to radio or heater or signals. My headlights turn on. My hazard lights light up when pressing brake pedal. Also I have to apply slight pressure on the column shifter in order for the starter to turn. Not sure if I left something loose when changing ignition switch? PLEASE HELP!!! I don’t know what else to check
     
  2. chengny

    chengny Full Access Member

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    Not sure if I left something loose when changing ignition switch?


    Maybe not loose; but rather, not properly adjusted. Just by looking quickly at the wiring diagrams for your Jimmy, it appears that the ignition switch contacts that feed both IGN circuits and the ACC circuit are not making (i.e. not being closed) - when the key is in the RUN position.

    HPIM2905.jpg

    The bolt holes on the switch bracket are elongated - to allow for adjustment.

    HPIM2902.jpg

    Try moving the switch up/down the column a bit and see if there is any change.
     
  3. Marcos

    Marcos Junior Member

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    Tried adjusting as mentioned above. I lost all contact now as the starter won’t turn even with applying pressure as I had before. I’ll try adjusting more tomorrow and see if I can get contact
     
  4. chengny

    chengny Full Access Member

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    Some additional information (both the switch and lock cylinder should have been in the "lock" position when the switch was installed):

    ST_330_83_1983_Chevrolet_Light_Truck_10_to_30_Service_Manual 313.jpg

    ST_330_83_1983_Chevrolet_Light_Truck_10_to_30_Service_Manual 314.jpg
     
  5. Charlie

    Charlie Full Access Member

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    :welcome:
     
  6. Marcos

    Marcos Junior Member

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    Thani for the info it is very much appreciated. I removed the ignition and switch and reinstalled per instructions above. Still no power to radio or heater or signals.

    Truck does start, headlights, taillights and wipers all appear to work properly.

    Do the heater, radio and sign
     
  7. Marcos

    Marcos Junior Member

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    Do the heater, radio and signAls use a different circuit?
     
  8. Marcos

    Marcos Junior Member

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    Quick update on things

    -jimmy starts
    -headlights and tailights work
    -wipers work
    -no radio
    -no heater

    -replaced fusible links at junction block and starter
    -replaced battery
    -replaced ignition switch
    -checked all fuses with tester all checked out ok with key turned to on position

    -can’t figure out why I have no power to radio or heater.
     
  9. chengny

    chengny Full Access Member

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    Couple of questions:

    1. Is the radio original or an aftermarket replacement - and is the associated wiring still as factory?

    2. Straight heat or AC system - and by "no heat", do you mean that the blower motor is inop?

    3. Are the turn signals still NFG?

    4. Important - Can you provide clear image of your fuse block - or verify that it is layed out like one of the blocks shown below:

    80 fb.JPG

    fb80.JPG
     
  10. Marcos

    Marcos Junior Member

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    Radio is aftermarket I couldn’t find any inline fuses

    Blower not turning on vehicle was originally equipped with ac but is not in use.

    Signals are inoperable

    Will verify fuses today
     
  11. chengny

    chengny Full Access Member

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    1. Radio - most modern head units use 2 power supplies. One is for memory (yellow) and is always hot from the battery. The other is the switched power supply (red) and is only hot when the ignition switch is in RUN/ACC.

    2. HVAC blower - there is no operation at all? None of the speeds work right? That's what strange. Say you had burned out all the elements in the resistor assembly (not unreasonable in light of the casualty), you would have no reduced blower speeds. But since power for blower HI speed operation by-passes the resistor stack, that should still be available.

    Conversely, if you had smoked the coil within the blower relay, the HI speed contacts would not close. That would prevent the blower from receiving the full 12 volts used for HI speed.

    It's as if it should be either one scenario or the other. Where are you checking for power supply to the HVAC control panel? Try to locate the connector just before the panel. It can be hard to find, but it should look like this:

    HPIM2967.jpg

    3. Turn Signals - maybe the little coil in the flasher relay got smoked. If your hazards still work, try interchanging that flasher with the T/S one.


    Do the heater, radio and signAls use a different circuit?

    Yes, they are all supplied by independent buses (within the fuse block) - and each bus has a different feed from the ignition switch.

    1. The bus that the RDO/IDLE fuse (and the WIPERS fuse) is fed from the ACC terminal - on BRN 4.

    2. The bus for the HVAC blower fuse comes off the IGN 3 terminal - on ORN 300

    3. The bus supplying the TURN B/U fuse (and the GAUGES fuse) is from the IGN 1 terminal via PNK 3


    What does this mean:

    checked all fuses with tester all checked out ok with key turned to on position

    Fuses are tested by pulling them from their sockets and checking for continuity - that's not something that can be done with the fuse installed in a hot circuit.

    Can I suggest something? I am going to anyway, so here:

    Start at the beginning of each leg of the affected circuits. The first voltage check should be done at the line (call it the inlet) side of each fuse's socket. Pull the fuse and - with the key in the RUN position - verify 12 VDC into each of the sockets at the associated boxes. The dwg shows the fuse block from the back so the sockets are reversed from the image above. Also check the fuses for continuity while they are out.

    The T/S circuit can be checked up to the line side of the flasher relay as well.

    lines and loads 2.JPG

    If you get voltage on the line side of the sockets (and the fuses are confirmed good)...that's about all you can do at the fuse block end without tearing into the wiring behind it.
     
    Last edited: Dec 27, 2018
    Snoots and 82sbshortbed like this.
  12. 82sbshortbed

    82sbshortbed Supporting Member Supporting Member

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    Nice post as always Chengny!
     
  13. chengny

    chengny Full Access Member

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    Thanks.
     
  14. WHEELMAN

    WHEELMAN Full Access Member

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    The key turns and there is a rod that pushed down in to that safety switch.do you have a floor dimmer switch.that could of went bad.that controls.some of electric.lights and what ever.check the wire plug.
     
  15. Marcos

    Marcos Junior Member

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    thank you for the info everyone, I haven't been able to dig around much, We have about 14" of snow outside and no garage to work in so its been a bit of delay on my end. Im planning on digging some more this weekend. I do have a couple of questions please.

    -It's as if it should be either one scenario or the other. Where are you checking for power supply to the HVAC control panel? Try to locate the connector just before the panel. It can be hard to find, but it should look like this:

    is this located on the inside of vehicle? under the dash?

    -Fuses are tested by pulling them from their sockets and checking for continuity - that's not something that can be done with the fuse installed in a hot circuit.

    I only have a circuit tester with a light, do I need a different type of tester to check voltage?

    -The key turns and there is a rod that pushed down in to that safety switch.do you have a floor dimmer switch.that could of went bad.that controls.some of electric.lights and what ever.check the wire plug

    I have a floor switch that changes from brights to dims, is this the switch you are mentioning?


    *Also forgot to mention that the Hazard Lights only turn on when pressing the Brake pedal and do not flash as intended, they remain lit until brake pedal is released.


    thank you again everyone, your time and assistance is greatly appreciated
     

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