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Idiot light for 4WD - where's it supposed to be?

Discussion in 'The Garage' started by AuH2O, Jan 6, 2007.

  1. AuH2O

    AuH2O 1/2 ton status

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    On the right side of my K5 steering column, opposite the service engine soon light, there's a red indicator light that I figured was for 4WD, but nothing's hooked up to it behind the dash. Instead, when I shift to 4WD a gauge-light type wedge-socket bulb dangling freely behind & below the gauge cluster lights up. Don't ask me why (but if anyone has an explanation I'm all ears). I just wanted to check with you guys if the red indicator light is indeed meant for 4WD - the manual makes no mention of it that I know - and if so I'll just reroute the wires from the other bulb and remove that one.
     
  2. b454rat

    b454rat 1/2 ton status Premium Member

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    The 4wd indicator is on the left gauge, is it the MPH?? I haven't owned in years?? I'd say if it lights up when you put it in 4wd, then its for the indicator....
     
  3. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    It is supposed to be on the Printed Circuit on the gague pod, to illuminate the Tell-Tale indicator, as you mention.
    It is a negative switched circuit to illuminate the bulb. Meaning, the gauge pod already has 12v+ to the light socket from the gauge power circuit, and when you shift into 4wd, the little switch in the transfercase completes the path to ground, illuminating the tell-tale.

    Why it would be separated out in it's own light socket seperate from the gauge pod itself, is pretty weird. I've never seen that.
     
  4. Dogman12

    Dogman12 1/2 ton status

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    I have an 85 Jimmy i bought a couple a months ago and it was doing the exact thing, just take the gauge cluster out and put the socket back in. If you undo the speedo cable from under the truck and put some slack in the cable you wont have to unhook the cable from the gauge cluster. should be a 20 min fix.
     
  5. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    You could just reach up behind dash and reinstall light. Only hard ones to get this way is blinkers. Also both 77 and 83 I have seen 4wd light on wires.





    oops edit :83 not 87
     
    Last edited: Jan 6, 2007
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Early 4WD indicator light wiring was separate of the instrument panel lighting. I would guess roughly 1981+ the indicator light wiring was integral with the panel.

    I only know for certain that a 1980 I pulled the harness from was set up separate, and that the mid-1980's clusters I have are not separate, nor is my 1991 cluster.
     
  7. Chrisblazzer89

    Chrisblazzer89 1/2 ton status

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    Hey i have an 88 blazer and wen i put my truck in 4WD no light comes on and i know that its sopposed to cas wen i took apart my gauge cluster i put a new bulb in the 4wd indicator light buit still noting? any input?
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd suspect either the switch on the t-case or the wiring more than anything else.

    PCB could be bad for that bulb as well. If the later switches are the same as described above, pulling the connector from the t-case and checking for a path to ground from the one wire, with 12V on the other, will prove the wiring TO the switch is good.

    The switch itself can be tested for continuity between the two terminals while shifting in/out of 4WD. From my experience the switches tend to get very picky on what movement turns them off/on. So you might not get continuity when shifting to 4WD, which means the switch is probably no good.
     
  9. Drey

    Drey 3/4 ton status

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    My 83 truck has that little light dangleing to, ive just never got around to slippin it back in, it doesnt really bother me, I know when its in 4x, Ill prolly do it sometime soon now seein as the truck is on the workbench right now
     
  10. AuH2O

    AuH2O 1/2 ton status

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    Alright, so then that bulb dangling behind the dash is indeed the proper 4WD lamp. Then I just have to reinstall it and fasten it properly - no biggie since I have most of it taken apart right now anyway. :D

    But then I wonder what that red bulb to the right of the column is... It's got its own hole in the dash and everything, but as I said, nothing's hooked up to it. I could snap a pic of it next time I'm in the garage if anyone wants to see it.
     
  11. Dogman12

    Dogman12 1/2 ton status

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    Mine has a choke light.

    Jesse
     
  12. BlaKK54Speed

    BlaKK54Speed 1/2 ton status

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    mine has a choke and a 4wd light but my 4wd light doesnt work. i didnt know there was one untill i took the gauges apart
     
  13. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    My cluster has the integrated 4wd light and I just wanted to know what colors the wires are leading from the dash to the switch?
    I think they might be white/black but not sure.
     
  14. diesel4me

    diesel4me 1 ton status Premium Member

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    here ya go..

    according to my Clymer books wiring diagram,the 4wd light uses a grey wire,and at the switch on the transfer case there is a black and a white wire the black wire goes to one side of the bulb,the grey one goes to the other side of the bulb and comes from the fuse box....this is a 1982 diagram I'm looking at....:crazy:
     
  15. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Thanks! :waytogo:

    I knew there were a black and white wire involved somehow.
     

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