Author Topic: 1978 trans am 403 wiring  (Read 705 times)

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Offline Carguru

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1978 trans am 403 wiring
« on: July 12, 2018, 10:21:26 PM »
Guys I just bought a 1978 trans am with a 403. I have a black with pink stripe wire hanging by the dizzy. It is cut and would like to know what it goes to. Also I have know gauge operations the tach and all gauges do not work they are pegged out. Any help would be great. Thank you.

Offline Stringer

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Re: 1978 trans am 403 wiring
« Reply #1 on: July 14, 2018, 06:31:49 PM »
Here is a basic overview of the engine bay wiring I put together for another persons post that you may find useful. I have also attached a crude drawing to help.

* There should be a ground strap at the back of the engine that runs to the firewall.
* The negative ground from the battery gets hooked to the engine.  There should be a stud near number 1 cylinder to mount it to.
* The positive from the battery goes directly to the starter.
* On the starter, on the same terminal as the positive cable, should be two red 10 gauge wires that run up form the starter along the firewall, to the
   bulk head, and into the interior.  I think both go to the ignition key with one being the main power wire.
* There should also be a red (?) 12 gauge wire going to the starter solenoid that also runs up to the bulk head, into the interior and to the ignition.
* There should be two 12 gauge wires running from the alternator connecting to the main power wire (the same wire coming from the starter) making a
   connection back at the firewall.  FYI --- Be sure to put a 40-50 amp fuse link in the main power wire after the connection from the alternator, else you
   run the risk of a fire if the starter grounds out or if you max out the amps when activating other systems due to other wiring problems or bypassed
* There should be one 12 gauge pink(?) wire that runs from the bulk head to the distributor which connects to the ignition coil on top of the distributor.
* I believe this wire is also connected to the ignition key. The rest of the wires connected to the distributor come from the ignition module inside the
   distributor itself and connect to the ignition coil on top the distributor.
* The tac is a tan wire that is hooked directly to the distributor at the ignition coil as well. (it is not shown on my wiring diagram but connects to the
   terminal next to the power wire on the ignition coil)
* There is also the wire to the temperature gage (green?) and oil sending unit (blue?) also not shown in the diagram. Those are in the same loom with
   the alternator and connect to the bulk head on the firewall.

Hope this helps
« Last Edit: July 14, 2018, 06:34:20 PM by Stringer »

Offline Aus78Formula

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Re: 1978 trans am 403 wiring
« Reply #2 on: July 15, 2018, 02:53:42 AM »
Get yourself a Service Manual, comes with diagrams. It will save others having to translate and post information from one they bought for their car.