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Lights on an 86 K-20

Discussion in 'Chevy Trucks' started by plowking35, Feb 1, 2003.

  1. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    I have an 86 K-20 that I am rebuilding, it was a basket case from someone else. Anyway I have 2 issues at hand, my guess is that they are related.
    1- I have no head lights, or parking lights. I have replaced the switch, but I am not getting power to the switch.
    2- The ALT is not charging.
    If anyone has ideas on where to look, I would apreciate it. Thanks in advance.
    Dino
     
  2. JCurtis

    JCurtis Banned
    Messages: 862

    Dino,

    wire may be broken, or the ground may be broken.

    Had something similar happen to me
     
  3. wyldman

    wyldman Member
    Messages: 3,265

    Sounds like a main power feed is broken somewhere.There is a terminal block on the firewall,that connect the battery feed to the alt,the battery feed to the starter,and if I remember correctly,one of those wires feeds the headlight switch.

    The alternator has a sense wire that goes into the main harness too,and if there is no connection there,and back to the battery,it won't charge.

    It could be the bulkhead connector where it goes through the firewall too.

    Check the wiring at the starter,as it feeds a lot of stuff as well.

    I have complete GM factory wiring harness diagrams,but they are at the shop,and I'm not going in till mon morning,unless it snows.If you want I could send them your way if it will help.

    I have rewired all our GM trucks,and there are better way's to run the underhood wiring,to get the all the fusible links away from the starter (where they corrode or get burnt\shorted),and make alt wiring simpler.I also add a separate starter solenoid so they start better.

    If your rebuilding this truck,I have all the diagrams I drew,and can get some pics for you too if you wish.Makes it alot easier to service and troubleshoot wiring when done this way too.

    Let me know if they will be of any help.
     
  4. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    Jeff, while I appreciate your reply, can you give me an idea on where to look.
    The wires at the junction block are all connected, but I am not sure if they are broken or not. The wire from the alt to the block is ok, I have tested that one out. The starter turns over fine, I need to start at those connections and make sure nothing is broke or burnt from the starter to the junction block. Thanks wyldemae, once again you have some very good suggestions.
    Just out of curiosity, that junction block has 2 posts on it, one side, the bigger terminal has all the connections, why are there two posts. It is the same way on my 84 and 89.
    Dino
     
  5. JCurtis

    JCurtis Banned
    Messages: 862

    Dino, I wish I could.....

    If I knew exactly were to look for the break it wouldnt make it interesting for you. I had to spend hours tracing and testing all sorts of wires, It may also be a bad ground which could be bad because of a broken ground wire, or a rusted/dirty connection.

    I may be buying another old one soon myself. I may just do what wyldman suggests and rewire the whole darn truck. I here there are some great wiring harnesses available nowadays.


    I hate to be so inconclusive, but with these old trucks you really must look at everything.

    Wish I could help more. Sorry Dino

    Maybe wyldmans reply can help you out more.:(
     
    Last edited: Feb 2, 2003
  6. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    Dino, there are 3 fusible links on that truck.

    1. A molded splice located at the starter solenoid "Bat" terminal, 14 gauge red wire.

    2. A 16 gauge red fusible link located at the junction block on the firewall to protect all unfused wiring of 12 gauge or larger. The link is molded into the bulkhead connector.

    3. The generator warning light nd field circuitry (16 gauge wire) is protected by a fusible link (20 gauge wire) used in the "battery feed to voltage regulator #3 terminal". The link is installed as a molded splice in the circuit at the junction block.

    So that "block" on the firewall has 2 fusible links molded into it. My guess is that is where the problem is, but that is only half the problem. You need to find the short that caused the link(s) to burn. Usually a dead short (wire touching metal), or wires actually melted together.

    Judging from your lack of power, everything is pointing to burned link(s).

    Did you remove the headlight fuse and check for power at the fuse block? IF the circuit has no power at the fuse block, there is definitely a burned link.

    Check for power at the bulkhead connector on the firewall BEFORE the fusible links. The fusible links have a large ring terminal on one end, and what looks almost like a rubber boot that holds a fuse on the other end (but they do not hold a fuse) the rubber boot is just to protect the soldered connection. The links are about 4" long.

    ~Chuck

    (I think* I have a pic of the fusible link somewhere, just need to find it)
     
  7. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    Believe it or not there isnt a fuse in the fuse block for the headlights. They must be hardwired with a fusable link direct to that junction block. Thanks for the info chuck. I knew that you would have the skinny on this.
    Time to do some tracking.
    Dino
     
    Last edited: Feb 2, 2003
  8. wyldman

    wyldman Member
    Messages: 3,265

    There is no headlamp fuse,there is a circuit breaker in the headlamp switch for that.

    Dino,I am heading into the shop this evening (next hour or so),so if you need wiring diagrams or other help,let me know.I could e-mail them or fax them to you if neccesary.
     
  9. wyldman

    wyldman Member
    Messages: 3,265

    Well I took a quick look at the wiring diagrams,and the common thing in the circuit for the headlamps,taillamps and charging system is one of the two fusible links at the starter battery terminal.It feeds the "sense wire" for the regulator at the alt plug,and feeds circuit 2 into the bulkhead connector,which goes to the fuse panel and the headlamp switch for headlamps and parking lamps.

    The headlamp switch get's it's power from the fuse panel.One fused circuit from the parking lamp fuse (orange),and one constant power,which comes in from the bulkhead connector,through the fuse panel (not fused though) to the switch (red).The tail lamp fuse is pulled off the same bulkhead feed as the red wire to the headlamp switch.

    A quick test would be to pull the little white plug off the alt and check for power.If you have none,it has to be one of the two links at the starter.

    My recommendation would be to pull all the wiring up from the starter,and run them directly to the battery with new fusible links.You may have to lengthen those two circuits,but it will eliminate any worry of the links ever corroding off,shorting out etc.
     
  10. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    Thanks Wyldman. The problem with electrical is that most repairs are easy, the hard part is finding them. Now that I have an area to look at I will start with those suggestions. I will keep you all posted, thanks again for all your help.
    Dino
     
  11. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    Sorry for not updating but I havent had time to work on the truck, but let me tell what did happen.
    My 84 K-20 all season has given us fits with batteries not charging, alt. not working right all the time, and starter solenoid issues.
    On monday it acted up again, well it turned out to be the fusable links down at the starter. I pulled them all up out of there like Chris suggested, and ran them staright to the battery, installed new fusable links, and the truck has been flawless since. So thanks again, with out the info you guys gave me, I would have been looking for hours, instead it was all repaired in less than 1 hr.
    Dino
     
  12. wyldman

    wyldman Member
    Messages: 3,265

    Good to hear you got it fixed.