Author Topic: Need Wiring Diagram  (Read 2280 times)

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Offline cal30_sniper

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Need Wiring Diagram
« on: January 07, 2007, 12:26:05 AM »
So, I'm still trying to roadworthy the '78, and I've run into another gremlin. The underhood wiring has been all chopped up, and I'm having a devil of a time trying to figure out what goes where. I'm still trying to get ahold of a shop manual, so I was wondering if anyone had a wiring diagram scan or something they could post. I need the underhood diagram for a 403 olds. The main thing I need to see is sending unit wires, and alternator wiring. The electric choke and the TH400 kickdown switch are both wired into the dark brown wire that comes off the alternator. I'm assuming this wire also is the same one that enters the harness along with the oil pressure sending unit, and a green wire (water temp sending unit perhaps?). Right now I've wired the dark brown wire that exits the harness at the front of the intake near the oil pressure sending unit, into the dark brown wire coming off the alternator, as this looked pretty natural. The big red wire coming off the alternator has been wired to the + side of the battery, spliced into the smaller guage wire on the batter post (not the large one that runs to the starter, the smaller one to the side of the terminal). Also, there is a black and orange wire that runs in the loom headed towards the distributor that has been cut, I'd like to see where that one goes too. All of the heater/ac wires have been cut out, and the horns are not currently working. Also, does anyone have any suggestions for a better place to splice in the kickdown switch (on the carb), and the electric choke, or is it fine to just leave them wired to the alternator (they are spliced into the dark brown wire which leads into the harness on the intake.) Once I can see a wiring diagram all my questions should be answered.

Thank you,

Levi

88 Trans AM GTA Flame Red/Tan, 350 TPI
86 C20 Suburban - 454/NV4500
73 Formula 350 - under construction

Offline Rick

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Need Wiring Diagram
« Reply #1 on: January 07, 2007, 12:31:36 AM »
I don't have a diagram for a 78 or for a 403, but didn't the 78/403 use a TH350 instead of a TH400?  That switch was made in 75 because of the space considerations for the catalytic converter, plus the engines got so whimpy that they didn't need the TH400 to handle the output any longer. :?

Or did somebody already swap out the TH350 for a TH400 on your car? :?

Offline Hitman

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Need Wiring Diagram
« Reply #2 on: January 07, 2007, 09:49:18 AM »
Since it is too large to post a photo of it in here, you can download the entire wiring diagram here:

http://www.78ta.com/media/Figure8-5.pdf
Brett Campbell
"Hitman"
www.78ta.com
www.ohiofirebirds.com
www.tanationals.com
1978 Trans Am

Offline cal30_sniper

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Need Wiring Diagram
« Reply #3 on: January 07, 2007, 10:21:10 AM »
Yes, you are absolutely correct about the transmission,  but after 30 years of backyard engineering, somehow these things do magically appear. The previous owners put a very nice TH400 in the car before they parked it. There was a lot of work done to the car, and the alternator went out and they parked it. I'm not sure why, but I am a happy camper. Thanks guys,

Levi

88 Trans AM GTA Flame Red/Tan, 350 TPI
86 C20 Suburban - 454/NV4500
73 Formula 350 - under construction