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Thread: Dash lights and others not working - need some help

  1. #1
    Join Date
    Dec 2006
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    Marietta, GA
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    Dash lights and others not working - need some help

    Also posted this to the SCCoA Facebook page.

    Need a little help figuring out an electrical issue on my 93 5 speed:

    Instrument cluster backlights not working (all the warning lamps do work)

    Radio cuts in and out. Completely loses power and won’t turn back on. Then randomly it comes on at the station I last had it on (premium sound system)

    None of the AC buttons light up except the rear window defroster and the temperature. But the AC itself works.


    I checked my fuses in the under dash panel and even though they looked good, I replaced with new.

  2. #2
    Join Date
    Dec 2007
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    Salem OR
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    Do the headlights work? If not, check the headlight fuse in the power control box under the hood.

    Does the rear glass defroster work?

    For the dash lights, power comes in from the power control box, then to the headlight switch, then to instrument lights. The circuit involves both primary and secondary junction blocks, and grounds.

    Can you get anything out of the instrument lights if you aggressively rotate the headlight switch a few times?

    About the radio...did you check the 5A 'Memory' fuse in the power control box?

  3. #3
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    Quote Originally Posted by KMT View Post
    Do the headlights work? If not, check the headlight fuse in the power control box under the hood.

    Does the rear glass defroster work?

    For the dash lights, power comes in from the power control box, then to the headlight switch, then to instrument lights. The circuit involves both primary and secondary junction blocks, and grounds.

    Can you get anything out of the instrument lights if you aggressively rotate the headlight switch a few times?

    About the radio...did you check the 5A 'Memory' fuse in the power control box?

    Rear window defroster light does come on. I assume it is functioning properly.

    Headlights work (both high and low beams).

    Nothing out of the instrument lights even after rotating lights multiple times. The warnings lights all seem to work properly though. It does seem as though the dimmer switch (auto headlight switch) does not make anything change. The light comes on but nothing happens.

    I did check the 5A memory fuse. It was fine, but I still replaced with new 5A fuse.
    Last edited by smms25; 03-04-2019 at 03:17 PM.

  4. #4
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    You might need to open the dash and see if power for the instrument lights is coming out of the headlight switch. I'd do that before throwing a new switch in it, just to confirm. Sounds like the rotary dimmer element inside might be busted/corroded. If you get in there and see an accumulation of white powder underneath the headlight pull switch, that can be another indicator of it being worn out...other than being 26 yrs' old, of course

    If the headlight switch is feeding variable current to the instrument lights, you may need to obtain an EVTM for your year SC and start checking grounds...the ones inside the dash would be high on my list. Don't forget that temporary grounds can help troubleshoot.

    The dash light circuit includes the lamps in the radio, but it shouldn't cause problems w/the radio power outright...those issues can sometimes be tied to a misbehaving multi-wire ignition switch down on the side of the column (note this ign. switch doesn't include the dash light circuit), especially if that component has been in service for a while.

    And of course the multi-function switch (turn/hi-lo beams etc.) involves the headlights and hi-beam indicator in the dash, but the headlight switch looks to be upstream and that's where the power for the dash lights comes from.

    Pls. note I'm working off the EVTM (wiring manual) for a '90 SC, so I may be making assumptions that are not common to your '93.
    Last edited by KMT; 03-05-2019 at 01:00 AM. Reason: added discuss about multi-function switch

  5. #5
    Join Date
    Jul 2005
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    438
    Good evening

    Seperate the steering column covers and check the ignition switch for the component separation and or loose electrical connector.



    Check for worn ignition key lock cylinder.


    https://www.autoblog.com/2016/01/11/...lock-cylinder/

  6. #6
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    Quote Originally Posted by sam jones View Post
    Good evening

    Seperate the steering column covers and check the ignition switch for the component separation and or loose electrical connector.



    Check for worn ignition key lock cylinder.


    https://www.autoblog.com/2016/01/11/...lock-cylinder/
    Sam - I am not sure how this has any impact on the issues I am having. The key lock cylinder seems to be functioning normally.

  7. #7
    Join Date
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    Good morning


    A bad key lock cylinder will change electrical circuit application due to the position of the ignition switch.

    Symptoms are:

    In start the anti lock light is on. The electrical function of HVAC is inop. Radio does not work. By slightly moving the key up the systems will power up.


    With the cars approaching 30 years the original key lock cylinder is on it last legs.

    A bad ignition switch can cause battery power disruption for start and accessory circuit.

  8. #8
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    Quote Originally Posted by sam jones View Post
    Good morning


    A bad key lock cylinder will change electrical circuit application due to the position of the ignition switch.

    Symptoms are:

    In start the anti lock light is on. The electrical function of HVAC is inop. Radio does not work. By slightly moving the key up the systems will power up.


    With the cars approaching 30 years the original key lock cylinder is on it last legs.

    A bad ignition switch can cause battery power disruption for start and accessory circuit.
    That's great, Sam.

    What part of the dash lights circuits go through the ignition switch?

    I mean, it's not bad advise, but it's not far from "Be sure to check oil and transmission fluid levels!" for the OP's problem.

    RwP

  9. #9
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    Quote Originally Posted by RalphP View Post
    That's great, Sam.

    What part of the dash lights circuits go through the ignition switch?

    I mean, it's not bad advise, but it's not far from "Be sure to check oil and transmission fluid levels!" for the OP's problem.

    RwP
    That's what I was thinking. I think if I had the issue Sam describes, that other lights/functions would be failing randomly as well.

    I will definitely keep this in mind as I go through everything, but does not seem to be the culprit for the symptoms I am having.

  10. #10
    Join Date
    Jul 2005
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    438
    Good morning


    You will need a EVTM (reference in other posts by KMT and others) troubleshooting Power Distribution to the fault components you identified.

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