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which wire feeds the fuse box?

Discussion in '40- & 55-Series Tech' started by bandy rooster, Aug 27, 2006.

  1. bandy rooster

    bandy rooster

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    I'm trying to repair the screwed up wiring in my '71, i'm just wondering if i'm right...

    the ignition should turn on a hot wire that relays power to the fuse box and allows the use of the fuse box while the ignition is on?

    what wire feeds the fuse box? i Have a thick white wire on the pass. side fender that i believe fed the power to the fuse block but don't see it at the main fuse block... I'm running a 350 as well... i just want the lights,fan,brake lights,turn signals and alt to start up when i turn the ignition swith on... I've also checked and rechecked the wiring diagram in tech links but i can't seem to find any "power wire" but maybe i'm just not understanding the concept of the fuse block.

    but how do i wire it to do that?

    i know i know broad questions but i don't have any more in depth information to tell...
     
  2. Coolerman

    Coolerman SILVER Star

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    Black wire with yellow stripe is the ignition feed to the fuse box on a stock 71. The brake llights are always fed power regardless of key as are the hazard lights. Turn signals are on with ignition. My web site has the 71 schematic on it along with a lot of other wiring information.

    What you should do is find the black/yellow wire from the key switch and run it to a 30 amp relay. Feed a fused 12 ga wire from the battery to the common on the relay. Then from the NO contact on the relay go back to the fuse block. The relay will turn on when the key is turned to ignition, powering on the relay. This makes the key switch last longer since it's no longer carrying all the current. Plus it will make the voltage at the fuse block higher by reducing the resistance of the circuit making lights brighter.

    HTH's!
     
  3. Pin_Head

    Pin_Head

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    Here is a wiring diagram for a 71.

    http://www.ih8mud.com/tech/72fj40-wire/71fj40_wire.gif

    Check it out and follow along below.

    All of the power for the chassis comes off of the battery cable where it attaches to the starter as a white wire. This goes to the + side of the amp meter, which is the main power distribution point. From the - side of the amp meter, the alternator power comes in and a white wire with blue stripe feeds one bus bar of the fuse block that is always hot regardless of the key. The brake lights and head lights run off of this bus. Even though you want the brake lights and head lights to work only with the key on, that is not the way it is and it isn't a good idea. If it was a good idea, Toyota would have done it that way.


    From the white wire with blue stripe at the fuse block, another black wire with red stripe feeds the common pole (AM) of the ignition switch. From the key on side (IG) a large black wire with yellow stripe runs to the fuse block where it powers the other bus bar that distributes power to things that are hot only when the key is on. this includes the accessories and the alternator. Note that the ignition wire is also black with yellow stripe, but it is not fused as it connects directly to the key side of the bus bar.

    I hate to disagree, but I don't think adding a relay is a good idea. Its contacts are just as likely to wear as the ignition switch and you have another component in the system to go wrong. If it was a good idea, Toyota would have done it.
     
  4. Coolerman

    Coolerman SILVER Star

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    Pin_Head I agree I would not add the function he wants, but, the key switched relay is used in all modern vehicles including Toyota. Design engineers have learned a few things about wiring in the past 30 years including using relays to switch power instead of running high current through a key switch. The reason Toyota did not use a lot of relays then was, they were not reliable enough. Relay contacts on automotive grade relays are now very reliable. If they wern't there would not be so many of them on new cars. Just make sure to get a relay designed for automotive use and rated higher than the current you expect it to handle.

    I will say this if you do add ANY mods to your electrical system do it right yourself, hire someone qualified to do it ,or don't do it at all. Poor wiring is not only the most complained about PO mod but it can be dangerous to you and others.

    Use quality automotive rated wire, connectors and relays. Fuse everything properly. Tie up loose wires. Also don't forget to document what you add so you can work on it later. The next owner will appreciate it!
     
    Last edited: Jan 4, 2007
  5. bandy rooster

    bandy rooster

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    thanks alot... its still a bit confusing for me i'm gonna go study the diagrams some more and draw it out for myself..in regards to me wanting the brake lights to come on when the ignition was on, i really didn't want that i was just naming things .. i dunno i'm a jackass sometimes... i'll be back later
     
  6. IDave

    IDave

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    By the way, that diagram is actually what a 1971 truck would be wired like, if it was a '69.

    The wire block went away in 7/70, for instance, and the headlight wires come from their respective sides.

    So, don't get too bogged down in those little details.

    For the most part, the wire colors and what they connect are consistant.
     
  7. honk

    honk

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    Nice catch Dave. I had thought the last of those buss bars or wiring blocks was in the '67 model but if it was '69.....well, fine. :)
     
  8. Coolerman

    Coolerman SILVER Star

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    Of all the diagrams I have, that one comes the closest to being correct for my 2/71. IDave was 7/70 the same time they got rid of the trailer socket change over switch? Has anyone actually seen one of those switches and sockets? I'd like to get ahold of those just to play around with them. [​IMG]

    Also if anyone knows of a more accurate 71 schematic let me know. The one in my FSM appears to be for a 73-74. It shows the fuse block with 8 fuses instead of the 6 that I have.
     
  9. IDave

    IDave

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    I've never seen a closer schematic. But it's different enough, if you're trying to learn, to be very confusing. I've never seen or heard of anyone having the trailer socket changeover. It really makes the rear wiring a headache to figure out having it in the diagram, though. :D

    Honk, I am going by what SOR has to say as far as when the wire blocks went away. It may have been much earlier, and they're simply wrong in their listing. I would have guessed it went with the bib parking lights. But I know for sure my 71 never had them.
     
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