What EA81 wiring is necessary to be kept for EJ22 swap?

[SaltyMike]

Hi everyone,

Finally in the wiring stage of my EJ swap and I'm working on cleaning up the EA81's wiring harness (at least what was in the engine bay). Besides obvious things such as headlights, wiper motor, etc, what wires need to be kept? I have my EJ22 harness thinned out by SJR and ready to go in. I've removed my A/C wires as I will not be keeping it. 

There's a large cluster of wires and relays that were located on the passenger side by the strut tower, and when I've seen pictures of EJ22 swapped 80s Subarus, I don't see any of those wires there. Before I cut them though I just want to be sure. I'll have to post the pictures in separate posts because they can't all fit in this one post. I've also read in Numbchux's swap guide that the EA starter relay needs to be kept but I can't find any wiring harness that show it. 

 Relays bolted to passenger side strut tower:

[SaltyMike]

Another relay, can't find in all my pictures where it was located. 

[SaltyMike]

Connections next to passenger side relays, fairly confident that none of them were connected to anything. 

[SaltyMike]

Another relay and what appears to be some kind of fuse box located, again, on passenger side. 

[el_freddo]

It seems that most of what you’ve shown above is the AC system. It will be separate to the main wiring looms and should be easy to remove.

The brown fuse box near the battery needs to be kept. 

There’s really not any wiring that needs to be removed for an EJ conversion, you should be able to easy convert back to EA81 after having an EJ in there. 

All you really need for the EJ conversion is: 
- permanent power (wire in the back up power to this too) 
- ignition power 
- start reference (tap into starter circuit) 
- oil pressure light/gauge wire (use EA wiring to the sensor) 
- engine temp gauge wire (use EA wiring again, EJ sender will change the behaviour of the EA gauge, this is well documented) 
- alternator wiring upgraded for EJ output and the plug wiring sorted to work with the EJ alternator. An ignition wire might need to be added to excite the coils to effectively turn the alternator on (stops the battery from draining out when not using the car) 
- tape up (isolate) and tuck the EA coil wiring away, or roll up and tape to the main loom if it can’t be tucked away  

From memory this is what’s needed to integrate the EJ loom into the EA loom to make it all work. It’s a good idea to put a fuse between each wire between the looms. That said I’ve never had one blow, but it’s safer to have one there than not to. 

Cheers 

Bennie 

[SaltyMike]

16 hours ago, el_freddo said:

It seems that most of what you’ve shown above is the AC system. It will be separate to the main wiring looms and should be easy to remove.

The brown fuse box near the battery needs to be kept. 

There’s really not any wiring that needs to be removed for an EJ conversion, you should be able to easy convert back to EA81 after having an EJ in there. 

All you really need for the EJ conversion is: 
- permanent power (wire in the back up power to this too) 
- ignition power 
- start reference (tap into starter circuit) 
- oil pressure light/gauge wire (use EA wiring to the sensor) 
- engine temp gauge wire (use EA wiring again, EJ sender will change the behaviour of the EA gauge, this is well documented) 
- alternator wiring upgraded for EJ output and the plug wiring sorted to work with the EJ alternator. An ignition wire might need to be added to excite the coils to effectively turn the alternator on (stops the battery from draining out when not using the car) 
- tape up (isolate) and tuck the EA coil wiring away, or roll up and tape to the main loom if it can’t be tucked away  

From memory this is what’s needed to integrate the EJ loom into the EA loom to make it all work. It’s a good idea to put a fuse between each wire between the looms. That said I’ve never had one blow, but it’s safer to have one there than not to. 

Cheers 

Bennie 

Thank you Bennie,

I completely understand that it’s not necessary to remove the Brat’s wiring harness when doing this swap considering it’s mostly going to be powered by the EJ harness, but I just figured I’d clean up the engine bay a little bit and get rid of the rat’s nest of wires I pulled from it. Just want to be safe before cutting anything though.

Just to confirm, that picture with the three relays and cylindrical connection point mounted on the metal bracket is all for the A/C? That’s the bulk of the wiring in the engine bay currently, and it just seems odd that there is so much wiring for just the A/C. Plus some of those relays have wires going to some important stuff, such as the headlights and the brake master cylinder. 

Through a quick parts lookup, I’m pretty sure the cylindrical connection all the way to the left with the hose exiting out the back is the refrigerant pressure switch, so I can rest assured that it’s for the A/C system.

[el_freddo]

The wiring going down to the headlights will be the thermo fan switch trigger when the AC is on. Just disconnect the two plugs, remove the AC wiring and reconnect the two plugs left in the main loom, they’ll clip together. 

The brake master cylinder wiring should stay with the main loom. That’s your low brake fluid warning light. 

That bank of relays will be all AC related - one for AC clutch, one for the second thermo fan no doubt, and if it references the headlights it’ll be to only run one thermo fan (designed to assume you’re driving at night when it’s generally cooler and also to conserve power usage on a small alternator), the third possibly to power the whole system. That canister on the end is for the idle up diaphragm located beside the carby. 

I’m 99% sure that info is correct. 

Cheers 

Bennie

[SaltyMike]

On 4/10/2023 at 2:37 AM, el_freddo said:

The wiring going down to the headlights will be the thermo fan switch trigger when the AC is on. Just disconnect the two plugs, remove the AC wiring and reconnect the two plugs left in the main loom, they’ll clip together. 

The brake master cylinder wiring should stay with the main loom. That’s your low brake fluid warning light. 

That bank of relays will be all AC related - one for AC clutch, one for the second thermo fan no doubt, and if it references the headlights it’ll be to only run one thermo fan (designed to assume you’re driving at night when it’s generally cooler and also to conserve power usage on a small alternator), the third possibly to power the whole system. That canister on the end is for the idle up diaphragm located beside the carby. 

I’m 99% sure that info is correct. 

Cheers 

Bennie

Great, thank you so much for your help. I'm trying to learn this wiring thing one step at a time haha.