I just started to remove the wiring harness for the 12a motor (for my 89 13b swap) only I cant seem to find where the body harness seperates from the engine harness.... I'm almost thinking it is one GIANT harness... where as the 89 one is two pieces.

 

There are two connectors on the driver's side fender wall under the master cylinders. They are the engine harness, but the ignition system wires are separate.

 

ok there was a snake on wires that ran right next to the firewall, is that what you are talking about?

I'm allmost positive that that connects to some of the interior stuff....

The 89 Harness I have, has 2 long connectors right where it enters the interior of the car and two more where it connects to the ECU. So it makes sence that the two would bridge around that area.

So I'm sort of confused as to what I need to do here. I am downloading the wiring diagram now... but its soooo sloowww!

 

Here's the question i have; wouldn't it be easier to leave the FB harness in there and just run the nessesary part of the FC harness for the FI and stuff? Seems to me that there is an aweful lot of stuff there that isn't affected by the swap and keeping the stock harness for that would be easier than having to adapt the FC one. just a thought.

 

well the plan is to use the engine harness, as it will have all the things necessary to run the 89 motor and FI. I'm runnign just about everything exactly as it is in the 89. I will keep the body harness for the 85. I just need to bridge the two somewhere.

Becuase I am using FI, I have to use the stock 89 ECU.

Now I am removing the 85 engine harness, as nothing on it will be used...

After speaking to a few FC people, it just seems like there is a body harness, and an engine harness, and they connect at one point.

So where would I have to bridge in the 89 engine harness?

 

well I just got done downloading the wiring diagram, and my worst fears have come true.

I do not see any way to bridge the two harnesses, the first gen harness is one giant piece, whereas the second gen is two pieces.

I'm thinking it might be easier to install the complete FC wiring harness.

Now I know that there are people out there that have done this..... HOW DID YOU DO IT??? Especially when I have seen peoples web sites that have successfully done it!

I'm stumped as hell here. ANY ideas or suggestions would be GREATLY appreciated.... expcept for going with an aftermarket ECU lol.

 

ok a new idea

exactly what does the ECU in the 85 12a even do?

in a carburated car it doesnt seem like you would need it at all! am I correct?

I'll never know but what would happen if you started the 12a car without the ecu plugged in? Would it start?

A few people have told me now that nothing in the interior even uses the ecu... which I find hard to believe. Dont the idiot lights rely off of it?

becuase from pauls website, http://my7.rx-7.org/Paul/index.htm it doesnt even look like he even touches the 12a harness and lets it dangle there!

Could someone explain how the electrical system works with the ECU?

 

The ecu controls the emmisions solenoids and the fuel pump relay and a few other things in an 85 car. Do you have the whole harness that runs from the ecu to the engine? We tried to tell you in your other post that there's no bridging of harnesses, there's nothing in the 85 one that would plug into your 89 stuff. If you have (or can make) all the wires that run between the engine and the ecu for the 89, you'll be set.

 

so so so much clearer now.

SO i just let the old ecu connectors dangle and every thing will work fine? (interior wise anyway)

The engine harness I have is the "whole shabang" with the rats nets attached and everything. So it will just go in.

One last question... while I was looking at pauls swap, this picture in particular caught my eye


HERE

On his ECU there is the last two connectors on the left (the ones wrapped in black) are not part of the engine harness..... where are they going???

 

Let them dangle, unplug them, cut them off, it doesn't matter one way or the other.

But do you have the harness that plugs into the 89 ecu?

Looks like the stock wiring that's usually located under the stereo. Like you said, it's not part of the 89 harness, so you can ignore it.

Are you going to use the 2nd gen ignition?

 

hornbm,
How do you plan to get the stock 89 OMP to work?

 

yes I do have the 89 harness that plugs into the 89 ECU. I'd probably be tearing my hear out with out it.

Also I am using the second gen ignition.

Its pretty much a COMPLETE swap from the 89.

As far as the OMP goes, I'm not going to worry about that just yet. I've heard there is a way to trick the ECU into letting you use a mechanical one, but I'm not sure.

One of the things that I just thought of, is the headlight rasing/lowering wiring. It connected to the old engine harness, and there is a spot for it on the new one BUT with this setup, how would I get the signal to the headlight asembly? There doesnt seem to be a path from point A to point B. Any ideas to improvise here?

 

bump