78 Wiring harness restoration question (1 Viewer)

[BEN QUINN]

I've been rewiring a 78 fj40 with a small block Chevy 350 with a HEI distributor I finally got it running today but I'm a little concerned about the wires going to the fuse box it doesn't seem that the wires are going to the correct location according to the wiring diagrams and just wanted to post a couple pics and get some feedback.

When I look at a wiring diagram the wires coming in and out of the fuse box do not match the wiring diagram I attached a pic and was hoping somebody could give me some input on whether these wires have been moved or I'm looking at the wrong wiring harness diagram.

The top of the fuse panel is at the top of the pic. Not upside down.

 

[ToyotaMatt]

I've been rewiring a 78 fj40 with a small block Chevy 350 with a HEI distributor I finally got it running today but I'm a little concerned about the wires going to the fuse box it doesn't seem that the wires are going to the correct location according to the wiring diagrams and just wanted to post a couple pics and get some feedback.

When I look at a wiring diagram the wires coming in and out of the fuse box do not match the wiring diagram I attached a pic and was hoping somebody could give me some input on whether these wires have been moved or I'm looking at the wrong wiring harness diagram.

The top of the fuse panel is at the top of the pic. Not upside down.

View attachment 1690549

View attachment 1690550

Can u post a few photos of the wire diagrams u are working with , that would help

This particular service manual has wire diagrams for each individual model year & a 1978 fj40 specifically

 

[Solace in Solitude]

@Coolerman has most, if not all, wiring schematics available here... the ‘78 FJ40 schematic is very good... I’ve used it a lot.

Coolerman's Electrical Schematic and FSM File Retrieval

 

[BEN QUINN]

Can u post a few photos of the wire diagrams u are working with , that would help

This particular service manual has wire diagrams for each individual model year & a 1978 fj40 specifically



View attachment 1690621

Yes, actually was using coolerman's diagram. Specifically the one attached;

 

[BEN QUINN]

To me 1 of the 2 big black yellow wires should be on the opposite side. There's other issues but I was starting with engine ignition. It runs but I'm now second guessing myself when looking at the diagram.

 

[ToyotaMatt]

To me 1 of the 2 big black yellow wires should be on the opposite side. There's other issues but I was starting with engine ignition. It runs but I'm now second guessing myself when looking at the diagram.

All Your large gauge wires belong on the same side of the fuse box , like they are now , there your B+ battery & ignition switch on & ACC Feeds to various circuts like your wipers , engine , Lights etc...

I notice the bottom blue wire on the fused ( small wires side ) has been severed ?

 

[BEN QUINN]

All Your large gauge wires belong on the same side of the fuse box , like they are now , there your B+ battery & ignition switch on & ACC Feeds to various circuts like your wipers , engine , Lights etc...

I notice the bottom blue wire on the fused ( small wires side ) has been severed ?

Yes it's been sniped but not sure why,

I guess what's most confusing are the wires are jumping through the fuse to the same color why.
For example, the black yellow ignition has a blue wire coming out the other side of the fuse. Or does that not matter?

 

[ToyotaMatt]

Yes it's been sniped but not sure why,

I guess what's most confusing are the wires are jumping through the fuse to the same color why.
For example, the black yellow ignition has a blue wire coming out the other side of the fuse. Or does that not matter?

just remember all the small gauge wires are Fused Feeds to various circuits ,

- for example the Green w/ Red stripe is the B+ feed for your parking Lights circuit and goes directly to the headlight switch connector to the left of your steering wheel

- the small gauge solid red is your headlight B+ fused feed and also goes to your headlight switch connector

- use a test light & see what large gauge wires have B+ power with the key off , it should be All the ones Fed By the white wire with the Blue stripe , that's constant battery voltage

- the large gauge blue wire with a red stripe B+ feed should be your ACC key position power , and the small gauge blue wire that's been cut at the bottom should be your radio fuse

- All the small gauge wires fed by the Big gauge black with yellow stripe are KEY ON power , like your ignition system & blower fan motors for heaters

I hope this helps

 

[BEN QUINN]

Thank you, it does help. I think since I got it running I'm going to connect everything and see what's not working. Then track down issues from there or I just pull the harness and redo everything.

 

[ToyotaMatt]

Good Deal !

Look at other year FJ40 wire diagrams like from 1975-1984 and see if one matches yours , i bet one does



also , i never asked is your truck a USA spec or a NON-USA spec import

 

[BEN QUINN]

So it runs and headlight, tail lights, brake lights, and turn signals work.

Turn signal work but both flash, one brighter than the other. If turning right, right flashes brighter, but both are flashing. Hazard switch was off.

Alternator regulator wires appear to looped together, trying to sort that out. Wiring diagram is a little confusing because this is a SBC 350 with modern alternator.

 

[ToyotaMatt]

- check all your turn signal bulbs first , make sure U are dealing with all the same wattage bulbs

- then take note on the wire diagram how all your turn signals / flashers All run thru the Hazard Switch , check its connector , then possibly the contacts inside the switch itself may be a bit crusty , if u have another known good hazard switch try it first to see if any Lumen difference goes away

- u also could be dealing with a simple bad connection / connector terminal maybe too

 

[BEN QUINN]

Turn signal fixed, flasher relay was not grounded.

What do you think about the alternator, like I said earlier, looks to be closed loop together. I guess I take that back, one is going to ignition black yellow and the other down to the fuse box

 

[ToyotaMatt]

Alternator B+ is the large Gauge white wire with the Blue stripe and should have constant key off power at the fuse box

at both of the wires in the green connector feeding your headlights , parking lights , horns , brake lights etc .

basically anything that would need to function without a key in the ignition



the large gauge black and yellow's in the green connector on the fuse box are separate circuits

 

[emac]

picture of my 77 fuse panel:

 

[BEN QUINN]

This is were the alt wiring is getting weird.
Far left is ignition black yellow spliced into the pink wire that goes to the regulator.

Next the 2 blk/y wires spliced into a single black yellow goes up from fuse box and is connected to the other wire coming from the regulator.
Does this seem correct for a 350 with gm alternator?