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Old 07-21-2007, 12:27 PM
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350 Chevy Alternator setup

I have a 1940 Plymouth pickup with a 1973-76 Chevy 350. I had to install a new ignition switch and I have new problems. When I first hooked it up I had the ignition going to a ignition power block for all the ignition needs. I also had the alt wire from the plug going to the ignition part of the switch. This started the engine but it would not turn off. When I take off the Alt wire it starts and kills but will not charge the battery. I thought it might have a bad diode but the power turns off the alt wire when the engine is shut off. Does someone have a simple wire diagram for this engine set up. The original owner make spagetti of the wiring and I am sorting through it. The Alt wire also has two other wires spliced in. I am still tracing these.
Jim

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Old 07-21-2007, 01:36 PM
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Doc here,

Well, the description you give is rather vague..but the main problem you are suffering is lack of isolation from the coil from the alternator output..

Traditionally, this is achieved through the ignition switch..things go wrong when "EXPERTS" start adding circuits on the lines and don't bother to check the termination points for the switched power..

You Did not say if this was a kit, stock , or something someone cobbled and hacked together for a wiring harness..so it is hard to be exact..

however : The logic flow should be as follows...

Starter solenoid, main battery cable, should have a 10 gauge wire going to the ignition and the alternator output wire..these wires will / should have fuse links AND have no other wires attached to them..(spliced) THIS puts "hot at all times" at the ignition switch and depending on how wired, the BATT terminal of the fuse buss. AND any memory support required for computer or CD players)

THEN, the "hot in run only" supplies power to the coil,(10 gauge usually pink,dedicated wire) and all the IGN ports on the switched side of the buss..Power only in run.

WHEN you shut off the ignition switch, the open contact provides isolation between the alternator output (on the B terminal on the solenoid,) and the coil..(hot in run only) If the output is on the wrong side of the switch, or has splices cross~wiring it to some item on the "hot in run only" SIDE, It wil keep the coil energized AFTER the ignition is shut off and battery output is removed from charged output..

So it looks like you need to troubleshoot that system..find the cross / mis~wire and correct it.


TYPICAL "GENERIC" SET UP FOR 70-72 gm TYPES..alternator/generator all the same for this purpose..

Doc
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Old 07-21-2007, 04:29 PM
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Sorry about the description being vague. If is difficult to describe. The wiring was thrown in and I am trying to make heads and tails of it. There are no colors to guide me. One wire starts at the alt(red) then is lt blue then dark blue then yellow then red. It all needs to be torn out but I am trying to get it running for now. I disconnected the alt wire to ignition and the truck still runs, charges and kills. There are a couple of splices and these must be the problem. The power antenna acts funny also when the truck is shut off. I am fairly new to this and am trying to learn. A cleaner set up would have helped.
Jim
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Old 07-21-2007, 05:35 PM
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Doc here,

The first step, is to remove the alternator output wire.

Next , isolate the wire that brings power from the battery (usually at the solenoid "B" terminal) and Remove it.

Acquire a Roll of 10 Gauge RED wire and 2 fuse links or MAXI Fuses, (65 to 75 amp would be good)..

Run the first red wire from the starter solenoid "B" terminal, to a Link, then STRAIGHT to the Ignition Switch..

Run the Second RED wire From the Starter solenoid to the link, STRAIGHT to the Alternator output stud. (You may , If wired this way, jump the smaller red wire from the alternator #3 terminal here also..but NO other wires!)

NEXT, locate the The "Hot in Run Only" wire coming off the ignition switch (has power only in on..) and follow that directly to the ballast or + Side of the coil or HEI.. Be sure it has NO splices..If it does, remove the wire, and replace it directly with a 10 gauge RED wire..

NEXT, locate The "Hot in Start" Only off the Ignition switch..(only has power in start ) follow that wire from the switch to the Neutral Safety switch, then the other side of the switch to the "S" terminal on the starter solenoid.

IF you have points..

The "I" terminal on the solenoid goes directly to the coil +, IF you have an HEI, this wire may be discarded.

Last, locate the "Hot in ACC Only " wire from the Ignition switch..This wire will go to the fuse buss ACC terminal only.

IF you have left over "Splice wires, " with a power lead, test each one and see what it controls..then find a corresponding fuse on the Fuse buss, and connect it there...do this until all the wires are back and connected.

IF you do this, the car will start, run, charge, and shut off..no problem..then you will have to work on the rest of the hacked harness to bring it right.

Are you running an amp gauge? If so, how is it hooked up? Is it stock? Is the alternator 1 wire, 3 wire, internal regulated or externally regulated? Do you have a charge lamp?

Doc
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Old 07-21-2007, 07:43 PM
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The Alt is a New 100 amp 3 wire internal reg. I can follow your instructions. I have installed a block for power, ACC, and ignition so I should be able to trace most of them. I installed VDO gauges, Volt meter. The post of the Alt goes to a power bar that goes to the battery. It is 4 gauge. The other wire could not handle the load and melted down. The new ignition switch has a bat term, acc term, ign term and starter term. I will give this a try. I need to clean this up.
Jim
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Old 07-25-2007, 04:48 AM
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Ignition switch help

Hey Doc, I am working on my ignition switch also. I want to rewire it completly because I cannot get my 68 firebird to shut off either. Could you tell me what each of this lugs on my switch should be connected to.
SOL
IGN
KEY-
KEY+
ACC
BAT
GRD
I got some diagrams from you in another post but because this is a stock harness with all kinds of splices and discolored wires I am getting lost. I have a bundle of spagetti sticking out of my dash now and am seeing stars tracing all these wires. Someone changed some wiring around in the past also so I need to start fresh with the ign and charging system. It has an external reg also , no hei
And what does it mean when people say "swiched side of fuse box and bat side of fuse box. Thank you
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Old 07-25-2007, 05:16 AM
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ign switch

I am not going to use the factory plug that goes to the ign switch for now. so to be safe is there any wires I should dissconnect from the fuse box other than the main power wires coming from the engine ?
Also what is the clutch safety switch purpose and can I bypass it for now and go direct to the solinoid? Thanks.
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Old 07-25-2007, 05:17 AM
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Quote:
Originally Posted by 1genbird
Hey Doc, I am working on my ignition switch also. I want to rewire it completly because I cannot get my 68 firebird to shut off either. Could you tell me what each of this lugs on my switch should be connected to.
SOL
IGN
KEY-
KEY+
ACC
BAT
GRD
I got some diagrams from you in another post but because this is a stock harness with all kinds of splices and discolored wires I am getting lost. I have a bundle of spagetti sticking out of my dash now and am seeing stars tracing all these wires. Someone changed some wiring around in the past also so I need to start fresh with the ign and charging system. It has an external reg also , no hei
And what does it mean when people say "swiched side of fuse box and bat side of fuse box. Thank you


Doc here,

Well, the first step I gather you have done...remove all the hacked wires...

The "Switched Side" of the fuse Buss is that side that becomes "hot" with the Ignition in the "On" or "Run" position..

The ACC side is that side of the buss that has power in both ACC and Run positions..

The BATT Side of the buss is that which has power at all times , regardless what position the key is in..
  • SOL: NSS switch to the "s" terminal on the starter.
  • IGN: to the Ballast resistor, then to the + side of the coil.
  • KEY-?? (maybe Gen Lamp? or key chime)
  • KEY + Switched side of the buss.
  • ACC: The Accessory side of the fuse buss.
  • BATT: From big lug on the solenoid terminal, Via Fuse link to the switch, "Hot At all Times".
  • GRD:Ground

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Old 07-25-2007, 05:26 AM
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Quote:
Originally Posted by 1genbird
I am not going to use the factory plug that goes to the ign switch for now. so to be safe is there any wires I should dissconnect from the fuse box other than the main power wires coming from the engine ?
Also what is the clutch safety switch purpose and can I bypass it for now and go direct to the solinoid? Thanks.

Doc here,

I haven't the foggiest idea what your doing...BUT NEVER bypass a NSS switch..you can injure or KILL yourself or other's (like your kids or the kid next door playing behind the car) Should it decide to start and run on it's own in GEAR..

Being sorry after doesn't make it right..and being negligent makes it a crime..

Doc
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