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  1. #1
    Join Date
    Dec 2002
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    fargo, ND
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    Default What would cause dash lights to go out when you turn on the headlights?

    On my 64 Skylark if I turn on the headlights the dash lights and tail lights go out? I tried to follow my wire diagram but it makes my head hurt!

    Any thoughts? I already replaced the headlight switch.
    Ed
    Mocha-Forever in my heart RIP
    1964 Buick Skylark Convertible (TSP 525hp 550TQ Iron head 464)
    1967 GS400 Hardtop Best ET 1.788 60 FT 12.68 @ 104.53
    1967 GS 400 4 spd Convertible (in boxes now)
    1968 Electra 225 Custom with 46k original miles
    1970 GS 350 Aqua Mist

  2. #2
    Join Date
    Jul 2009
    Location
    optiontown
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    142

    Default Re: What would cause dash lights to go out when you turn on the headlights?

    Quote Originally Posted by Topless64-455 View Post
    On my 64 Skylark if I turn on the headlights the dash lights and tail lights go out? I tried to follow my wire diagram but it makes my head hurt!

    Any thoughts? I already replaced the headlight switch.
    usually when you have a dash lite problem it's with the dash grounds.in your case the circuit that feeds power to the taillights also feeds power to the dash lites.the reason this was designed this way was to alert the driver that his tail lamps where not working.if it was just the dash lites I'd say a faulty ground.this is not the case here and it looks like your loosing power to the headlite switch.using a test lite check your tail lamp fuse on both sides to assure your getting continuity.if its ok then check for power at the headlite switch .The large(red 12 Gauge) feeds the switch.do this first because this is the power feed for the headlamps.the dash lites are fed from the headlite switch reostat so check the dk green 18 gauge wire for power when the dash lites are on,this feeds the dash fuse and the fuse also can be checked.the next step is brn/white stripe wire feeding the h-lite switch.this feeds power from the fuse block all the time and if you have power there then check the Dk Brown 16 gauge wire coming out of the h-lite switch.with the switch on you should have power.this wire leads to the t-lamps.if all checks out then you may have a defective switch.it's possible to have this happen but I bet you find you have a combination of 2 problems aggravating each other.make sure as you do these test you have someone watch your outside lites.movement sometimes causes a temporary fix.Bill
    Last edited by sky64; 04-20-2013 at 06:01 AM. Reason: added some details

  3. #3
    Join Date
    Aug 2002
    Location
    Huntsville
    Posts
    2,248

    Default Re: What would cause dash lights to go out when you turn on the headlights?

    Dash grounds
    Scott

  4. #4
    Join Date
    Feb 2002
    Location
    LI,NY
    Posts
    16,125

    Default Re: What would cause dash lights to go out when you turn on the headlights?

    Quote Originally Posted by sky64 View Post
    usually when you have a dash lite problem it's with the dash grounds.in your case the circuit that feeds power to the taillights also feeds power to the dash lites.the reason this was designed this way was to alert the driver that his tail lamps where not working.if it was just the dash lites I'd say a faulty ground.this is not the case here and it looks like your loosing power to the headlite switch.using a test lite check your tail lamp fuse on both sides to assure your getting continuity.if its ok then check for power at the headlite switch .The large(red 12 Gauge) feeds the switch.do this first because this is the power feed for the headlamps.the dash lites are fed from the headlite switch reostat so check the dk green 18 gauge wire for power when the dash lites are on,this feeds the dash fuse and the fuse also can be checked.the next step is brn/white stripe wire feeding the h-lite switch.this feeds power from the fuse block all the time and if you have power there then check the Dk Brown 16 gauge wire coming out of the h-lite switch.with the switch on you should have power.this wire leads to the t-lamps.if all checks out then you may have a defective switch.it's possible to have this happen but I bet you find you have a combination of 2 problems aggravating each other.make sure as you do these test you have someone watch your outside lites.movement sometimes causes a temporary fix.Bill
    Excellent.
    Jason Cook
    BPG #1675
    "Expert in obsolete technology"

    1968 Riviera GS- some assembly required
    1969 Riviera GS- my first car
    1970 Stage 1 4 speed Aquamist
    1971 GS 455 11.93@113.36
    1971 Skylark Custom convertible
    1972 GS-350 project car
    1970 Stellar Industries vintage go kart

    When tyranny becomes law, rebellion becomes duty

  5. #5
    Join Date
    Dec 2002
    Location
    fargo, ND
    Posts
    4,596

    Default Re: What would cause dash lights to go out when you turn on the headlights?

    Bill thank you very much for the detailed testing. This is make it easy for me trouble shoot. I replaced the orginal switch because I thought that was the issue so I will assume the switch is good and go from there. I wont be able to work on it for a couple of weeks but I will report back.

    Thanks again
    Ed
    Mocha-Forever in my heart RIP
    1964 Buick Skylark Convertible (TSP 525hp 550TQ Iron head 464)
    1967 GS400 Hardtop Best ET 1.788 60 FT 12.68 @ 104.53
    1967 GS 400 4 spd Convertible (in boxes now)
    1968 Electra 225 Custom with 46k original miles
    1970 GS 350 Aqua Mist

  6. #6
    Join Date
    Jul 2014
    Posts
    1

    Default Re: What would cause dash lights to go out when you turn on the headlights?

    I have a similar problem on my 64 skylark convertible and plan to follow your trouble shooting advice. The tail lights and dash lights don't turn on even thought the headlights brake lights and signals work. I also understand that tail lights are not fused but rather are on fuse able links. Do you know where the fuse able links for the tail lights and dash lights are located? Can you direct me to a wiring diagram?

  7. #7
    Join Date
    Aug 2013
    Location
    St Louis Missouri
    Posts
    91

    Default Re: What would cause dash lights to go out when you turn on the headlights?

    It's a long shot--but I'll tell my story.
    84 Olds Delta 88.
    Headlights off= brake lights worked fine, but front parking lights and dash lights would come on when the brake was applied.
    Headlights on= dash lights worked, front parking lights worked, but brake lights would not go out.
    The cause was an incorrect brake light bulb. Go figure.
    True story.
    Brian

 

 

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