72 chevota wiring help please (1 Viewer)

[franklin40]

i have a 1972 fj40 that had a chevy 350 swap that was poorly done so i’m trying to fix it. now that i have the motor properly placed i’m trying to figure out wha the heck is going on with the wiring.
here goes. the PO decided not to use the stock gauges so put some aftermarket ones in. i’m just going to run with them for now. so far i have a white/red stripe coming out of the left upper firewall harness that goes to the alternator as the excite wire. i think that’s correct. that’s about it!

off the charge post of the alternator i have a white/blue stripe wire that goes to the upper left firewall harness but to a black/ red stripe as well as a wire to the aftermarket amp meter.

the other wire from the amp meter then come back and splices to a red (i think that’s the headlights wire) as well and a white/blue stripe and a pure white. these are the same upper left wiring harness. i don’t know and can’t figure out from the wiring diagram what those wires are doing.

from the right side fire wall i have a small black/yellow strip that goes to the ign side of my hei distributor and i have a black/white stripe going to the starter. from what i can figure these are correct.

can anyone tell me what the heck is going on with the alternator wiring and what those bunch of wires spliced together are doing. i don’t even see a white/blue stripe wire on the wiring diagram

 

[franklin40]

here’s the diagram i’ve been trying to follow but man am i confused!

 

[pb4ugo]

First I'd get rid of that wiring diagram. You can go to Coolermans website globalsoftware-inc and find a better one. The white blue is the charge wire coming off the stk alt. It looks like you have a mess on your hands. Personally id cut out all the non syk wiring and start over
You can then add your gauges. There's are simpler ways to hook this stuff up. Do you still have the gauge cluster with the gauges? Do you want to continue running an amp meter? What all gauges do you have?

 

[franklin40]

cheers. a better diagram would be helpful. my plan is to get rid of all that wiring. i just can’t figure out what need to be hooked back up to what? i do have the stock cluster. i originally though it may have been burned out but i’m guessing this was easier for the PO to use. this may be the best time to figure out how to make the original gauges work instead.

currently i have amp, oil pressure and temp on aftermarket gauges. i think stock the fuel gauge is the only functioning accessory gauge.

 

[sggoat]

please take a look at the FAQ for gauge/clusters--BJ40 green is prob THE guru for these
Capn Conch has a 72 chevota -give him a shout--he has info on the wiring as well

 

[pb4ugo]

Coolermans website should have a Haynes 72 diagram plus others yrs, haynes and fsm. Most of the models use a lot of the same basic wiring. Checkout madelectricals website too. They have tech tips using the gm alt. There's good reading. I dont understand why your po did what he did. The bare connection with the white/Blue(wl) wire looks stk and is hot. In stk form the wl supplies power to the harness when running. This power is sent thru the amp meter to the batt and vise versa(charge/discharge). I think the neg at the amp meter is wl and the + side is white going to the batt. It needs a fusible link at the batt so it won't burn up the harness. Personally I don't care for the stk setup. I disabled the amp meter and set mine up with an idiot light or you can run a voltmeter.

 

[franklin40]

went to coolermans site. i don’t see a 72 diagram. from what i’ve read there are some changes from 71-72 and again from 72-73. maybe my issues are similar between years but i just don’t know. i’m not strong with wiring or even wiring diagrams.

 

[pb4ugo]

On his site at the top of the green panel is a link to schematics. Then scroll down to 72 73 model i think its from a Haynes manual. You're going to have to get familiar with diagrams. The color codes tell what each wire does and where it goes. I wish we could say do this or that, but your po has really altered the harness, It's hard to tell what he did from here. It probably can be put back together. Hopefully you wont have to pull the harness to repair it. If you checkout mad electrical they have a good explanation on the use of ammeter, and also how to wire gm alts.

 

[franklin40]

when you look close at the numbers they are all ‘73 diagrams. here’s a screen shot

 

[Booch]

Figure 2A

From one of my painless wire directions when re-wired the vehicle a few years ago

 

[franklin40]

that’s exactly where i was hoping to go. i just need to figure out what wires are what on my harness. there are definitely some that didn’t come with the truck and some of the ones that did are all bastardized. but yes that wiring is my end game.

 

[pb4ugo]

So looking at the links from your screen shot, the one listed just below 72-73 FJ40 is close enuff. The schematic is listed as 72-73 on the diagram. There are subtle differences thru the yrs but the charging systems wiring is essentially the same, and the wire id doesn't really change. Toyota didnt change the colors function. My 75 still used WL for the alt charge wire, W going to the batt with a fusible link . The colors are the same for the turn and park lights, even though the tail lights are different, they just terminate differently.

The 2 figures that Booch posted will eliminate the function of the ammeter, which I prefer. My setup is similar to his 1st diagram listed as 2A. I ran a 6ga wire from the alt charge terminal to the batt and added a fusible link, which is probably overkill. I use the white wire(914) for my idiot light. You can buy a new GM alt plug at any auto parts store. You'll find a similar diagram in mad electrical.

 

[bikersmurf]

First off, the stock ammeter is good for a 45-50 amp alternator. It only goes to +/- 30 amps.

In all likelihood, you’ll have/want a higher output alternator so I’d recommend wiring it directly to the battery rather than through the ammeter.

Second, it’s easy to use stock senders for the original gauges. Probably easier than cleaning up the aftermarket wiring. I’ll admit I’m on my phone and haven’t read everything posted above.

If you get a stock oil sender and a brass 15* angle fitting it’ll screw into the SBC block.

If you get an 2F adapter that screws into the water sender hole, you can screw your stock sender into the SBC head.

Once the stock senders are in place, it’s a matter of connecting the single wire for each and you’ll have two more stock gauges working.

 

[franklin40]

i have a 1977 engine 2f siting on my shop floor. i should have the oil sender which i searched and it seems to be the same across those years. the coolant temp might be different but i’ll figure that out. i like the idea of getting the stock gauges going. i need to figure out how to hook up that one white and red that are splicer to the white/blue stripe. not sure where they should go to at this point but i’ll figure it out!!

thanks for all the help it’s changed my direction a bit which will probably make things easier and this way i only do it once as i was eventually hoping to get the stock gauges going anyway.

 

[pb4ugo]

If you go by Booch's figure 2A you will no longer be using the WL wire. It will be hot but no longer hooked up, mines seal up and hidden into the harness. It needs to be made so it doesn't ground out. According to the Coolerman diagram the WR goes to the voltage regulator. Looking at your pics( 4th pic down) of the the WL,W, WL , looks like it is a factory crimp. Theres' no need to do anything with that crimp other than make sure it's sealed up so it doesn't ground. The factory Voltage regulator is no longer needed. The GM alt has an internal VR. The concerning part you describe is the PO's use of the ammeter, which I would eliminate, it will not work anyway . Either use a voltmeter or an idiot light. I would also remove the gauge cluster and bypass the factory ammeter, but as @bikersmurf mentioned it is not necessary depending on your alt output.

 

[pb4ugo]

I guess if you wanted to cut out the WR you could. If you leave it alone it will be hot at the VR plug which should be protected by the plug itself and no longer plugged in. The FJ40's white wire at the batt will need a fusible link and will be suppling power to the harness if you go by the 2A diagram.

 

[Vandal FJ]

I believe that I have to use the 1971 schematic for my Jan 1972? The 1972 doesn't officially start until like Sept. Models.
That might help with it...

 

[bikersmurf]

Currently my ammeter only shows the drain of the electrical system because the alternator output goes directly to the battery. I have a Faria voltmeter that I've removed from it's housing and I'll put in place of the ammeter to measure the voltage and give me feedback that way. I still need to finish installing it into my spare cluster and install it. The rest of my gauges work as designed by Toyota, but aren't super accurate, but work well enough to warn me of problems if something is broken.

 

[Vandal FJ]

View attachment 3230000
Figure 2A

View attachment 3230001

From one of my painless wire directions when re-wired the vehicle a few years ago

I have to use the diode in mine, or it won't shut down. Easy fix. Once I realized the PO had the two alt wires BACKWARDS to try and cure the same issue!

 

[franklin40]

k quick question. i have a 77 water temp sender but an early 72 gauge. they apparently are different in function and i don’t believe they will talk to each other properly. if i’m wrong please tell me. i’m planning on buying an early 72 sender but i don’t know what thread size they are for an adapter. the 77 is an m16 thread from what i’ve read. is the early 72 the same?

i have an adapter coming for the oil pressure sender. they are apparently the same from 58 up so i’ll use what i have there.