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What's this relay?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ryan B., Feb 22, 2003.

  1. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    What\'s this relay?

    I've been re-doing a lot of the wiring in my 1972 K/5 today..
    I chased down three wires that are in the loom with the ignition + wire.
    Blue
    Black
    Brown with white pinstrip
    i followed them they go through the factory harness clip on the firewall through to an oval can relay under the dash.
    All those wires and the relay is dead... I'm just wondering what it was for?

    Another weird thing i found was one wire coming off the starter, went to a splice to two yellow wires,and to another splice that was just getting b+ from the fuse box.. With the key in the run position I ended up cutting that wire in half, it is dead coming from the starter, it is getting b+ from the fuse box? .
    WTF? I ended up using that wire for my electric choke because my electric choke has been hooked to the ignition feed wire for the HEI... not good.
    I cut the wire shorter and eliminated that splice so it only feeds the HEI now.
    I ended up searching here and on another chevy truck board and a guy with a '72 truck on another site said those yellow wires were just dead wires coming off the starter that he got rid of? Sounds like the same deal.

    Where does the B+ wire for the HEI come from??? A fused location on the fusebox, is this correct? And the fusebox gets fed from the wire that goes to the battery with a fusible link.?

    I'm trying to get rid of all last bits of the "Booty Fab" the previous owner did that i haven't fixed yet.
    I need to go find my manuals with the wiring diagrams. /forums/images/graemlins/thumb.gif

    Thanks for some input.
    Ryan
     
  2. therobzilla

    therobzilla 1/2 ton status

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    Re: What\'s this relay?

    Ryan,

    I have a complete wiring diagram for the 72 blazer, as I have rewired mine at least twice, once for the TPI and last time was about 2 weeks ago when I replaced all the dash gauges for aftermarket ones. I can send you some copies of it, but I won't be able to get them to you until thursday or friday of next week. Is this too late for you??

    Let me know, and if you are intreste, I will make some copies and send them to you and or post on my webshots.

    Rob
     
  3. R72K5

    R72K5 Banned

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    Re: What\'s this relay?

    the yellow wire runs from R terminal on starter solenoid up to distributor to feed that, you dont need it anymore if you want to convert to HEI, get rid of it and the white wires too from firewall plug harness near brakes booster

    oval can relay doesnt ring a bell, especialy with those wire colors, what color is relay and how big is it and what it made of and where exaclty and how is it mounted ? any numbers or brand name on it ?
     
  4. therobzilla

    therobzilla 1/2 ton status

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    Re: What\'s this relay?

    Ryan,

    The Blue, Black & Brown w/ white stripe is the TCS relay. It something like Transmission Control Solonoid, ??? Not completely sure, but one this I am sure of is you don't need it. I ripped mine out years ago. But make sure it's not in the circut for the Temp gauge. I think they are part of the same circut. Check it out, I think the DK Blue 20 Gauge wire has a jumper the goes to the Temp sending unit on the driver side of the block. If so you can cut the pigtail and splice them together.

    I will address the other question on another post.

    Rob
     
  5. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: What\'s this relay?

    Rob, I'll have to go find my manuals that have diagrams in them.
    What are your diagrams out of... What brand manual?
    THanks.

    Also the can relay is a silver can relay kinda oval and it's screwed to the firewall under the dash, it's probally case grounded how it's mounted? It's not important, just wondering what it was for. /forums/images/graemlins/confused.gif
     
  6. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: What\'s this relay?

    I re-did that green wire that goes to the driver's side Coolant temp sensor. it just goes through the firewall grommit to the gauge, i believe.
     
  7. therobzilla

    therobzilla 1/2 ton status

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    Re: What\'s this relay?

    Ryan,

    Randy is right about the yellow wires, you can get rid of if you are going to HEI, the tow yellow wire off the starter were, 1. for the coil positive switched and the other was the lead for the 3A circut into the fuse box, for Ignition feed. If you lose both of these wires, the "Ignition" spade on the fuse box will not work. It will be a dead spade in the fuse panel. Not biggie, but I need mine for the TPI, and to feed a slew of other opions that are switched on my blazer. The yellow wires should be 20 gauge wires, really thin wires.

    Hope this helps.

    Rob
     
  8. therobzilla

    therobzilla 1/2 ton status

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    Re: What\'s this relay?

    Ryan,

    I have the Chevy factory 1972 Service Manual and a Factroy Chevy Complete Chassis Wiriring Manual. Orignial Manuals.

    Rob
     
  9. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: What\'s this relay?

    Yes that did help, Thank you. /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif

    Shure I'd be interested in those just to have on hand for future reference. Thanks a bunch man!
     
  10. therobzilla

    therobzilla 1/2 ton status

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    Re: What\'s this relay?

    Ryan,

    No problem. I will get them together next week. I will look up the exact meaning of TCS. I use to remember what this meant, but it's been a while.

    It's one of these.

    Transmission Control Sensor
    Tempature Control Solonoid

    I'll find out.

    Rob
     
  11. therobzilla

    therobzilla 1/2 ton status

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    Re: What\'s this relay?

    Ryan,

    TCS means right out of the book, "Transmission Control Switch", It was a switch for the TH400 that mounted on the extension of the gas pedal bracket. It was for controling the shifting and such on the TH400's. It was wired normal/standard with all 1gen blazer.

    Unless you have a TH400, it's worthless.

    Rob
     
  12. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Re: What\'s this relay?

    Interesting! So it was wired out into the engine compartment loom with the ignition and starter wire but ultimatly to nothing, and just cut off from the factory?
    Nice! /forums/images/graemlins/thumb.gif
    Was a TH-400 even an option for a first gen Blazer!? /forums/images/graemlins/confused.gif
     
  13. R72K5

    R72K5 Banned

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    Re: What\'s this relay?

    i was gonna say tranny controlled spark timing in my first reply but i was thinking oval shaped relay in my head because of the description of it, the tcs relay is mouned next to horn relay on 67-72's


    tcs is actually an emissions setup.
    it retards timing in low forward range and in reverse and is nothing to do with th400 kickdown,

    th400 kickdown was mounted to gas pedal on most 71-up trucks and is orange wire


    [ QUOTE ]
    Ryan,

    TCS means right out of the book, "Transmission Control Switch", It was a switch for the TH400 that mounted on the extension of the gas pedal bracket. It was for controling the shifting and such on the TH400's. It was wired normal/standard with all 1gen blazer.

    Unless you have a TH400, it's worthless.

    Rob

    [/ QUOTE ]
     

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