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fuse panel ?? please help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by testosterone, Jul 27, 2002.

  1. testosterone

    testosterone Registered Member

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    I have no power to the left side of my fuse panel in my 90 Blazer. This portion of the fuse block holds the ECM, Horn/Dimmer, and Tail/CTSY. All of the other sections work fine except for this column. I have also checked the orange wires hat plug into the tops of the fuse panel...the one labled 'battery' at the upper top corner fo the column and the other orange one that is down two below that one that also reads battery. There is no power comming out of that wire..should those be hot leads comming INTO the box or comming OUT of the box??The truck will not start w/o jumping the fuse box to get it power to that side. I used to have a jumper going from the bad side 'pwr' connection right above the shunt to the working side and it starts just fine. I crawl under her and look at the starter wires and there is a fat orange wire that has a fuse link on it...power comes out of it..find the two red wires leading into the firewall..one has power to it..this one is comming from the junction block. Traced the other wire out and it plugs to the alt. This wire has no power going through it (is it suppoesed to?) I jump the non working wire to power and it fires right up..take the jumper off and it dies..SO I plug the jumper back into the fuse block and check the wire again (at this point i have taken the jumper off of the fire wall...the jumper is inside on the fuse box like it has been for the past year)...so after jumping it inside the fuse panel the red wire comming from the alt is hot..I dont understand why this is..if there is something wrong with the fuse panel why can i jump it from inside?? can i just run a hot lead from the junction or battery and splice it into the non-working red wire in the firewall??
    sorry if this is confusing or that im asking too many questions but i need help with this in a bad way..im sick and tired of driving my little neon around and looking at the big beast just sitting there in the parking lot.
    Any help would be GREATLY apprecitated.
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Are you talking about the junction block on the fire wall next to the brake booster? It has power on the side leading to the starter but not on the side that runs into the back of the fuse block? If so I think that junction block is also a fuse link. It has a strip of metal between the two post that acts as a fuse. One wire from the starter runs to the ignition switch on the steering colum. it also controls the swtiched circuits on the fuse box. There will 2-3 Fuse links down by the starter. One leads to the the block on the fire wall. One goes to the alternator main lead and I think one goes dirrectly to the starter switch. I might be wrong on how thats wired. The one going to the switch may be y in at the block or on the otherside of the Fuselink at the starter and not have it's own fuse link. Been a while since I have messed with any of that on my trucks and mine are both mid to late 70's so might have changed a little by 90.
    Yours is the truck that had an under hood fire and the harness had to be replaced right? All the harness are very close from about 78-79 up but there are some minor changes. If jumpering the block on the fire wall doesn't restore power to the box then I would hit your local large library branch and they have the factory manual on Microfisch. Year spicific 10c a copy. find the wiring diagrams and start checking the pin out on what your fuse box is supose to have and what that harness has. Also it's possible that a pin poped out of the junction block so take a few minutes and make sure that hasn't happend.
     
  3. testosterone

    testosterone Registered Member

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    Thank you for the response...the red wire comming drom the junction box by the brake booster has power. The other red wire that is comming from the alt has no power...when i jump the alt wire then the fuse panel is fine. I can jump it from the fire wall BEFORE the fuse box or jump is from the fuse box itself and it starts..but no jumper no start /forums/images/icons/confused.gif
    Also, from what i saw on my starter there was only one fuseable link...
    I guess the real question is should that wire comming from the alt be hot at all times or only when the truck is running..and then again the prob comes into play that it wont run unless its hot...jeez...
    Thanks..i truely do appreciate all the help..
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Uhhhhhhh only one fused wire at the starter? I know both my trucks have two. The fat wire screwed onto the back of the alternator should have juice all the time. It's the wire that charges the battery. The other wire that plugs in is a feild wire that engergizes the alternator to get ti to start chaging. It's switched. The diods in the alternator stop the current from back flowing through the alternator and causing a discharge. Right now I'm thinking one of the harness wires didn't get hooked up to the starter. There is a wire down at the starter that comes from the switch it goes on the small terminal. So out of that harness there should be at least 3 wires counting the starter trigger down there with two possibly 3 going through fusible links. If you have that metal tube it's possible one got pulled up in side it and your not able to see it. I just chucked a 85 engine harness that was on a motor I got out of the junk yard /forums/images/icons/frown.gif It was screwed up but it was complete enough I could have sorted it out to tell you what went where. /forums/images/icons/frown.gif
    I'll try to dig out my shop manual in a little bit and look at the digram.
     
  5. testosterone

    testosterone Registered Member

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    well there are three wires off the starter..only one looks to have a fused link though..if i remember correctly..one oragnge one with a fused link, then a blue and brown wire also, neither of which are hot.
    ive been thinking...if the panel is jumped from inside..and the truck starts..and if the truck starts when the wires are jumped from the firewall then that means that the circuit should be complete right?? i figure if there was a short in between then no matter how it was jumped it wouldnt start or atleast the alt wouldnt charge.
    maybe its a bad alt?? the power lead going in is hot..but the plug comming out of it, the red wire isnt hot..im not sure its supposed to be though. I guess i wll have to figure all of that out..thanks
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Only 1 of the wires should not have power at the starter. As I recall it's the brown wire with the white stripe that is the wire to cick the starter. The Orange and Blue should both be on the big terminal that also has the Fat cable off the battery.
    I'm getting ready to run up the street. I'll roll under the 79 real quick and double check the wires I have and where they go. The starter and main power feeds should be the same even though the trucks are 11 years appart. Trying to figure out where my shop manual is. Wasn't on my Shelf inside so it's either in the garage or in one of the trucks. I'll try to find it also.
    I'll get back to you in a little bit.
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Ok I have 3 different Diagrams One is the Haynse for 77-80, Haynes for 81-87 and one from a copy from the library for a 85, and all stink! LOL.
    At the starter on all three it shows The PPL that I asume is purple goes to the small terminal It's the trigger from the key to engage the starter.
    Now here is the pisser. All three digrams indicate two red Fusible links but it doesn;t show the color before the link. My truck is filthy underneith and What I thought was brown is what the digrams show as the purple wire. Since the truck starts with the fuse box jumped we can forget that wire.
    now under my truck I had two wires going to the lug on the same lug as the main battery cable. One of those two wires then has a "Y" with TWO Fuseable links. Both the wires after the fuse links will be red. One of those wires goes to the plug on the alternator. Check for 12v at one of the wires on the plug on the top of the alternator. Should be 12v. No power then blown fuse link.
    The other wire goes to the fuse box plug on the fire wall to terminal 2J.
    looking at the plug that's the big wire going into the left harness on the bottom left. Check for 12V on that wire at the plug. As near as I can tell that appears to be the wire going to the ignition switch and it comes back and powers the majority of the switched circuits (acc, igg) and a couple power wires on the very right top of the fuse box. No power then the other Fusible link is blown. I think this wire is ok from your description.
    Ok the other wire going to the big lug on the starter is also shown as having a fuisble link (so that makes a total of 3 fusibles at near the starter). On my 79 the fuse link was a couple inches back and I had to pull it out of the loom to find the fuse link. This wire runs dirrectly to the terminal block on the fire wall. Again that wire after the link becomes red.
    Now all three diagrams show that on the other side of the terminal block that there is another fusible link then the wire "Y". One side of the "Y" goes to the big main wire on the Alternator. The other wire goes to terminal 2E on the plug on the fire wall.
    2E if looking at that plug look at top left. go one row right and 1 row down and it will be a thick red wire. Gets into some real spaghettie here but it looks like that is the feed to the left side of the fuse box.
    2E I think is your problem. Here is how I think you can confirm with a test light or Volt meter. Test the left lug on the terminal block on the fire wall. Should have 12v there. If no power there then one of the fuse links is blown down at the starter.
    If there is power there then check the right terminal. No power there then a problem with the Terminal block.
    If you got power on both lugs of the terminal block then Grab the biggest red wire on the right side. That should be the fuse link. Pull the plastic cover back on the harness. The Y was about 6-8 inches down from the terminal on my 79. Probe both those wires and see if you have 12v there. No power then the Fuse link right there is blown. I am pretty sure that is were your problem is. /forums/images/icons/grin.gif
    Now try to trace the wire that goes over too the plug on the fire wall. I couldn't tell is if the actual fuse link it the short 6-8 inch length or if it's a little further down. I think it's the short lenght before the Y.
    If by some odd chance you have 12v on both those wires then at the plug check 2E for power. I doubt there will be power though. Looking at the diagrams it looks like that has all the right connections to coencide with what is not working on your truck.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Anything hooked to the + batt lug on the starter *should* have constant 12V unless a fusible link is blown.

    Heres a neat trick though (and apparently totally unrelated to your problem) if you pull the 30A circuit breaker on the right (passenger) side of the fuse panel, all the accessory terminals above it will die. : )

    Still sounds like a fusible link problem, I thought all the wires from the starter (two fusible links rust or orange colored and the ppl "start" wire) went to the cab??

    There is also the junction block for those wires above and to the drivers side of the distributor, which all wires there (2 IIRC) should have 12volts as well, since they come off the starter.
     
  9. testosterone

    testosterone Registered Member

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    Well I just got done tearing everything apart and still nothing. I appreciate all the help and advice though, I really do. The fused links all seem to be intact as they all have power comming out of them. What I dont understand is why I only have one fused link comming from the starter. Also my alt gets a straight feed from the wire comming off of the battery. I have taken pics of all of this stuff. Can you guys spot anything out of the ordinary. I checked the red alt wire comming out of the alt plug, when the junction box is jumped (as i have shown in the pic) the red alt wire goes hot and the truck starts. With no jumper that wire is not hot. I tore the fuse panel out and looked behind it and all seems fine. From what I could see on the schematic it does not appear that the two sides of the fuse block are joined in anyway. Now, the junction block on the firewall next to the master cylinder is fine..power at both lugs. Im starting to get kinda dissapointed that I cant get this prob fixed. I think that a trip to the electrical shop and draining my savings account is next. Would it hurt anything if i just hooked up a direct feed from the junction block to that red starter wire to make it hot????
    thanks again guys.
    here is the link to the pics
    http://community.webshots.com/user/dto
     
  10. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    2E had power to it? That is what looks like feeds the left side of the box.. The deisels had a wire straight off the alternator to the battery instead of going through the junction block. Yours should not. I think the fuse link was smoked and somebody bypassed it and that's why you can't find it at the starter. It could have blown the fuse link at the junction block off the right side and that's why your not getting power over at 2E on the harness plug below the the master cylinder where it goes into the cab.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    I can only offer some tips here, because without my manual in front of my, I'm very limited : )

    As I recall, with the two fusible links from the starter, you can have one quit working, and still ahve power to some items. As I recall, headlights are the main thing on one fusible link, ignition is on the other.

    Does the wiring appear to be "hacked" up in any way, shape or form? You can easily tell factory stuff, they never used butt connectors, one wrap of electrical tape, and so on /forums/images/icons/smile.gif As a matter of fact, I don't believe GM used solder anywhere except on splices, and even then, the splices used crimp "connectors" as well as solder.

    MJ has the '85 wiring diagrams online, can you do me a favor and compare that to your '90 wiring diagrams? If they are similar, I'll see if I can't look through them with you, and see what we can't find. Obviously some stuff is going to be different, but the actual starter/ignition circuits changed VERY little, car, truck, etc., over about 30 years.
     
  12. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I looked at the diagrams again this morning.
    It seems to me that at some point somebody rerouted the alternator wire straight to the battery. Nothing I can find shows anything but the Deisel trucks should have it wired that way. The diagrams still show that the wire from the alternator to the Right side of the junction block should still be there even on the Diesels. That wire T's into the wire that runs to the plug on the firewall.
    Terminal 2E is the connection on the plug. Looking at the plug you will have all the slots for potential connections. Look at the top left count one row right and one row down and there should be a thick red wire. That should be the wire comming from the block. Probe it for 12v. That has to have constant power and if it doesn't then that's where the problem is. Trace that wire back to the Junction block. The digrams show a Fusible link between the plug and junction block. With the wires pulled out of the harnesss on my 79 by the junction block I can see the big lump where the Fuselink joins the regular wire. Thats hanging down between the valve cover and the Brake booster is where it's located on my truck. Then it goes under the the booster over to the plug.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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  14. testosterone

    testosterone Registered Member

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    Thanks guys. I was gonna check the truck tonite when I got home from work. But much to my suprise when I pulled into the parking lot to my apt complex it was taped off with crime scene tape and the place was crawling with police. Turns out that somebody killed a young lady and stuffed her body in between the dumpsters about 100 feet from my truck. Needles to say I wasnt able to sit there and start tearing more stuff out of my truck. Hopefully if there are no other happenings tommorow I will dig into the fuse panel again. Thanks again for all the input...u guys dont know how much help it is to me.
    When you guys make it out to Vegas i will buy you a beer.
     
  15. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Uhhhhh Gee I think I will pass on coming out ........you know with all the MURDERS and stuff. /forums/images/icons/crazy.gif
    What a thing to come home too.
     
  16. testosterone

    testosterone Registered Member

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    haha..i understand. I am actually moving into a new place..gated, very ritzy...suprised they let me in haha....the strip is a safe place to be though, unless you get stuck at the blackjack tables... /forums/images/icons/grin.gif
     

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