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Ekectrical ? and yes I did a search.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JROSS, Dec 3, 2002.

  1. JROSS

    JROSS 1/2 ton status

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    When I turn on the dome lights with the switch it causes my Stereo to cutout and it loses all the presets. Same thing happens when I push in the lighter. Also, when I push in the lighter the dome lights will come on dim. When just trying to turn on the dome lights only the floor light comes on.

    This all started when I found out my lighter was disconnected. The previous owner had cut the wire going to the stock lighter and rerouted it to some extra power receptacles. Ever since I rewired the stock lighter I have been having the above problems. My first thought was a fuse for the dome lights, but when I push in the lighter it does get hot and the dome lights come on dim. The Stereo is wire to the stock hot wire, and I added a batt lead from the same terminal that powers the clock.

    Sorry so long but I spent an hour going through the wiring diagram last night and don't know what to check next.
    /forums/images/graemlins/1zhelp.gif
    <font color="blue">UPDATE! </font color>
    /forums/images/graemlins/crazy.gif Guess I'm the winner of The DA of the week Award. After all the testing fuses and reading wiring diagrams I finally got some fuses and what do you know! /forums/images/graemlins/thumb.gif
    What kills me is I swore that I visually check that fuse and it was reading OK on the circuit tester, also I was getting voltage at the lighter. Anyway everything is back the way it should be, except I broke the connector on the back of the lighter trying to hook it back up. All this to get the lighter working and now its broken.

    /forums/images/graemlins/laugh.gifThanks for everyones input. /forums/images/graemlins/laugh.gif /forums/images/graemlins/laugh.gif /forums/images/graemlins/k5.gif
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    My solution would be to cut out every piece of extraneous (non-factory) crap, and start over by wiring stuff in that needs power, through the fuse panel, not by splicing into stuff.

    I know you didn't do this, so no slam on you, but the reason not to mess with factory wiring is so you can actually diagnose the problem. I'd bet you'd agree right about now, electrical gremlins are NO fun to find. (but fairly easy if the wiring is stock)

    With the PO adding, cutting, splicing and generally making a mess of the harness, tracking down what does what is made much more difficult. A wiring diagram does you NO good if the wiring isn't stock.

    Sounds to me though, at least with the radio bit, that for some reason the dome light is hooked up to the radio, and is probably pushing too much voltage into something like a display dimmer in the radio or something. Being an '81, your truck would never have had a constant 12V radio source (for the presets/clock) nor would it have had a dimmer wire hooked up to the headlights, that later digital units had, so both of those would have been added to make a radio with memory/clock work.

    My advice once again is to cut all the extra crap out, solder and shrink wrap ALL connections/splices that you cut on, and add the power wires etc. for the radio from the fuse panel accessory terminals.
     
  3. shane74

    shane74 1/2 ton status

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    Sounds like your drawing too much power off of one circuit. Also, check the ground for the stereo. If it's loose or bad, it'll cause all kinds of funky problems. Another thing to try, rewire the stereo hot leads to the constant hot off the battery (the one you added) and see if the other issues still exist. If they do, then it's more than likely that the PO did some creative wiring somewhere that you haven't found yet. Just my $0.02.
     
  4. sosamantx

    sosamantx 1/2 ton status

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    this isn't really related (well some what), but just an experience that happened to me in the past. i installed a car stereo in my friends mom's car (ford) many many moons ago. well, when i was through the darn thing wouldn't work, it had me puzzled, i wound up having to call it a day (well it was night). the next morning when she was going to work, she turned on her headlights (or wipers), and then the radio came on. it turned out (i went to the dealer and asked one of the shop managers), that i wired the ground to the wrong thing. the plug that was for the radio, was the hot, voltage when the headlights are on (for the stock radio), and something else.

    basically, i'd disconnect the cigarette lighter from where you have it now. that should be a piece of cake (it should only be a hot, and a ground). and, just run a new hot from your fuse panel. as mentioned in one of the responses to you, i'd check/run new wires for your stereo, and check the ground. as for the dome light, i don't really know, but i think if you fix these 2 problems, maybe the other will get fixed??

    Also, make your your battery is properly grounded as well!
     
  5. JROSS

    JROSS 1/2 ton status

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    First off thanks for all of your suggestions. /forums/images/graemlins/laugh.gif You mentioned a ground on the lighter. I only found one wire coming off the lighter. I assumed it grounded itself.

    I'm thinking I will disconnect the lighter first off. Then recheck the ground for the Stereo, right now I have it grounded to the dash instead of the stock ground wire. /forums/images/graemlins/thumb.gif
     
  6. hammer

    hammer 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    . When just trying to turn on the dome lights only the floor light comes on.


    [/ QUOTE ] There is floor lights?
    wow need to get them fixed!
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Yep, its right above the tranny tunnel. Odd little mount for it.
     
  8. driney

    driney 1/2 ton status Premium Member

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    My best guess is the power to the lighter and the memory wire to the stereo are wired to the ground side of the dome light circuit. The wire to the dome lights is hot all the time and at the low amount of current the memory wire needs it would probably supply enough current through the dome lights to keep the presets. When you push in the lighter the voltage drops because now the lighter and dome lights are in series. The dome lights come on dim because they are grounding through the lighter. Also when you try to turn on the dome lights you are grounding the side of the circuit your radio is drawing from and the voltage potential drops to near zero. Anyway, thats my theory. /forums/images/graemlins/thumb.gif
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    </font><blockquote><font class="small">In reply to:</font><hr />
    This all started when I found out my lighter was disconnected. The previous owner had cut the wire going to the stock lighter and rerouted it to some extra power receptacles. Ever since I rewired the stock lighter I have been having the above problems.

    [/ QUOTE ]

    Rule one of trouble shooting...Check your previous work...undue the last thing you did.
    MAYBE the previous owner disconnected this for the very reason your having problems.
     
  10. JROSS

    JROSS 1/2 ton status

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    Allright, this weekend I reversed everything I did before I had the problem, but I still have the same problem. I even disconnected the stereo and the lighter and still have no dome lights. I checked my fuses and had power to both sides. One thing I did notice is the dome lights have been wired to the batt plug on the fuse box instead of from the back of the box. Something else that has me confused is, that there is power to the lighter and the dome lights off the fuse block but yet the dome lights still don't work. (the bulbs are good). Anyway, my next step is going to wire the dome lights to the back side of the fuse block and replace my fuses and hope for the best. Any suggestions are welcome.
    /forums/images/graemlins/ears.gif
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, why not check for voltage on the front of the fuse panel? I've messed around with a few fuse panels, and have NEVER seen one messed up on the back side. Not even PO's want to take it apart to access and screw with that part.

    If you've got voltage on the front side, then the light wire will have voltage too, so the power isn't reaching the dome light either because the wire is damaged, or something is hooked in preventing it from working right.

    Obviously with the door closed, turning the light switch knowb fully counterclockwise will turn on the dome light, but now that I think about it, I don't think the dome light is "soft" wired into the fuse panel, its a constant 12V line out of the fuse panel to the headlight switch, and as such, it more than likely is ALWAYS from the back of the fuse panel.

    The dome light is tied into the door jam switches and underdash lighting (above the tranny tunnel) as well, so if those are working, that just leads me to believe that the dome light wiring itself is hosed, not the fuse panel.

    Have you pulled the dome light housing out of the roof to check it's wiring there? Even new the wires to the dome light look burnt, must be how GM assembled it, but if the wires are broken, they'd likely be broken up there, that's the easiest place to access them to screw the wiring up for a PO.
     
  12. JROSS

    JROSS 1/2 ton status

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    I get what your saying, but whats got me is that everything worked fine until I tried to hook up the lighter, so unless its a coincidence that something happen to the wiring at the same time it should still all work (this makes me think I popped a fuse when messing with the lighter. This may be a dum question, but is there anyway I could be getting power on both sides of the fuse but still have a bad fuse.
    At this point I really don't care about the lighter (only wanted it for a portable CD), I just want my dome lights to work without messing with the stereo. Also, just found out it does the same thing to the stereo when I use the switch foe the rear window. /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/1zhelp.gif
     
  13. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    TAKE the fuse out and check it. If your testing with a volt meter it may have a power backflow and you would read 12v on both sides of the fuse even though the fuse is blown. If your truck is old enough to have glass fuses it could have slow blow fuse in it and you can read power on both sides of the fuse and it still be blown.
    These trucks run straight hot to the light and all switching on and off is done by controlling the ground.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    If you have power on both sides of the fuse, unless the blade isn't contacting in the panel, it's working. A continuity test would likely show that too, but just as easily, you can swap a known good fuse from another location into that one.

    It's extremely likely when something doesn't work after messing with wiring, that a brittle connection broke, or a corroded connection was jiggled just enough to keep the wire from making a good contact.

    Have you checked out MJ's wiring diagram for the routing of the wiring, or even the wiring diagrams in the back of a Haynes manual??
     
  15. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Ohh yeah I bet blowing the horn gets the dome light on /forums/images/graemlins/grin.gif This has happend before but I don't recall what the finnal fix was. It was something with the wiring shorts out and blow the fuse.
     
  16. JROSS

    JROSS 1/2 ton status

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    Well I'll try a known good fuse and if that does't work it will be time to pull the dash off and really get into it. I have the GM service manual with the wiring diagrams for everything.
    Thanks for all the input guys. I'm hoping I just have a bad fuse since I really didn't mess with too much, mabey I accidentally hit a hot wire and popped a fuse. If not a fuse off comes the dash.
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't think you'll have to really yank much out of the dash, I would imagine one or two wires up at the headlight switch (which you can pull with the dash intact) and the rest are strung at the base of the dash, underneath the glove box, under the carpet, etc.

    It sounds pretty simple, figure out if the headlight switch is working (that could be a possibility I guess) and if it is, why the dome light isn't "seeing" ground or voltage, when it should.
     
  18. JROSS

    JROSS 1/2 ton status

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    Update, see above post. /forums/images/graemlins/thumb.gif
     

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