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Old 07-18-2007, 05:42 AM
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Doc , I need a diagram 68 firebird

Hi , I bought another 68 firebird 400 and the guy has some funky wiring going on. It is a stock motor with external regulator, 3 wire alt, horn relay,stock ignition system.When I turn the key it cranks very slow and when i turn off the key it keeps cranking. I had to pull the battery cables to stop it. (SCARY)since then I have replaced the ignition switch with the key cylinder and pulled the starter and it and the solinoid tested good at napa.I just would like to see a wiring diagram for this vehicle before I blow up something or start a fire. because he has the wiring a mess. thanks John

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Old 07-18-2007, 05:59 AM
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Doc ,additional info on the 68 firebird

The guy replaced the starter and sol ,voltage reg and coil ,I know I need to replace all the ground straps and cables, you taught me how to do that on my other car.along with making sure all fuse links are in place and not burnt.He has a 1foot long 4 ga cable hooked to a 100 amp breaker wired to the hot 4 ga battery cable off the breaker is a 10 ga black wire going to the horn relay middle terminal. and a red 10 ga running to a soldered splice with 1 10 ga going to # 3 on vol reg ,10 ga wire to firewall , and 10 ga going to terminal on the right side of the horn relay.
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Old 07-18-2007, 07:08 AM
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Try the AutoZone web site for that wiring diagram. I think they go back as far as '68
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Old 07-18-2007, 07:27 AM
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Doc here,

Start system:



Run system:



Did I understand correctly, you have a 100 amp breaker between the battery and the starter solenoid?

If so, that's why it won't crank..it's a wonder it did not blow apart when you hit "Start" as a starter can pull up to 1000 CCA's ..

IF that is the way it is, pull that breaker OUT and toss it..

Get a proper fuse link or maxi fuse nothing else..the logic flow is: Battery cable 4 ga to solenoid, the buss support wire to the solenoid (the fuse link goes on this line) Alternator output to solenoid ( It's fuse link goes on this line) The "S" wire from the solenoid to the starter "Start " Position only, the "I" or "R" wire to the coil + wire DIRECT with no splices..

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Old 07-18-2007, 01:19 PM
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68 firebird follow up

Thanks for the diagram .Am I correct :
The 10 ga purple wire goes from the S on the solinoid to the fire wall w/ fuse link
10 ga wire from R on solinoid to + coil directly
4 ga from +bat to solinoid big lug (obviously no spices)
??? I must be missing the buss support wire ????????
I replaced the 100 amp breaker with a 60 amp maxi fuse that is on a line of 10 ga from battery positive ,to a factory splice that goes to alternator(I am going to put a fuse link between the splice and alternater also)voltage regulator, and to the connector next to the bat connector on the horn relay.The Bat connection on the relay has a 10 ga going to the firewall.?I actually am not 100 % sure that it is a horn relay , Could it be a starter relay? I dont see a horn relay in any schematics.
Thanks John
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Old 07-18-2007, 04:49 PM
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Quote:
Originally Posted by 1genbird
Thanks for the diagram .Am I correct :
The 10 ga purple wire goes from the S on the solinoid to the fire wall w/ fuse link
10 ga wire from R on solinoid to + coil directly
4 ga from +bat to solinoid big lug (obviously no spices)
??? I must be missing the buss support wire ????????
I replaced the 100 amp breaker with a 60 amp maxi fuse that is on a line of 10 ga from battery positive ,to a factory splice that goes to alternator(I am going to put a fuse link between the splice and alternater also)voltage regulator, and to the connector next to the bat connector on the horn relay.The Bat connection on the relay has a 10 ga going to the firewall.?I actually am not 100 % sure that it is a horn relay , Could it be a starter relay? I dont see a horn relay in any schematics.
Thanks John
Doc here,

No Fuse link on purple..It goes DIRECT from the start position on the ignition, to the NSS Switch, to the "S" terminal (small one closest to the block) on the solenoid.

The "I" terminal goes direct from the solenoid to the + side of the coil PAST the ballast resistor .. This is secondary Ignition for crank boost...IF you converted to HEI , you no longer need this wire at all.

Battery Cable + terminal to the Big terminal on the starter solenoid, no splices or diversions.

Battery Cable - to any handy block bolt at or near the starter.

The 10 gauge wire you spliced a New Fuse link into will go from the Alternator output to the big terminal on the starter.(fuse link end).

The Battery Connector on your HORN relay IS your main buss support wire, to test, turn on some lights or other electrical, and pull the wire..the Body SHOULD go dead..This wire will get a fuse link, and should be located to the big bolt on the starter solenoid. It may , However , be left where it is, but is better located with the other + wires and links at the solenoid.

There is NO starter relay (stock) for that car..that will be the horn relay, to test pull the horn wires and activate the horn, It should go "Click"..

Doc
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Old 07-18-2007, 04:51 PM
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Hey doc

Hi < I just rewired everything I talked about and it started right up and sounds good. I bought it on ebay so I was pretty worried. No hei just stock wiring , 4 speed muncie , 400 motor.
The problem still exists though , it does not shut off with the key. It is not the alt because I disconnected all the wires before starting it.
I have the purple 10 ga wire that comes from the factory plug connected to the "s" terminal on the solinoid and a 10 ga from the R on the solinoid to the coil +. The only other wire involved is a bout a 20 ga pink wire from the coil to the fire wall plug. All wiring is now original except what I did. I took out all his high power stereo wiring .
your diagram shows a generator but I have an alternator.And I have hot wires running to the horn relay. Where can I get an original diagram including the stock Hot splices that also connect to the horn relay.Thankyou very much
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Old 07-18-2007, 06:13 PM
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Quote:
Originally Posted by 1genbird
Hi < I just rewired everything I talked about and it started right up and sounds good. I bought it on ebay so I was pretty worried. No hei just stock wiring , 4 speed muncie , 400 motor.
The problem still exists though , it does not shut off with the key. It is not the alt because I disconnected all the wires before starting it.
I have the purple 10 ga wire that comes from the factory plug connected to the "s" terminal on the solinoid and a 10 ga from the R on the solinoid to the coil +. The only other wire involved is a bout a 20 ga pink wire from the coil to the fire wall plug. All wiring is now original except what I did. I took out all his high power stereo wiring .
your diagram shows a generator but I have an alternator.And I have hot wires running to the horn relay. Where can I get an original diagram including the stock Hot splices that also connect to the horn relay.Thankyou very much
Doc here,

GM calls it's alternators a Generator..after-all, they are an AC generator!

The reason you are getting run on, is one of the wires feeding the coil, is remaining hot after shut down..(like a hotwire) remove them one at a time, and test, the one that holds the coil hot, is the offender..(BTW: if left alone, your battery will die, and the coil and points will burn out)...

This usually happens when guy's who know enough to be dangerous, will hook accessories into the "Hot In Run Only" line from the ignition, (a DEDICATED coil line only) and this backfeeds through ground and the fuse buss and puts spurious power on the coil, removing the ignition switch as a source of isolation..(That's a lot harder to say in text than do...whew.. )you get run on because you still have a partial (resistive) path to power.

Good to hear you made a righteous Deal though!

Doc
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Old 07-19-2007, 12:52 AM
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Doc here,

Here is your horn system diagram.

Doc
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