EJ conversion - ECU wire to trigger thermo fans

[el_freddo]

G'day fellow conversion nuts!

I'm after the wire or a "how to" wire up the thermo fans to the ECU of the EJ engine.

I've got an '88 L series with an EJ22 installed.  I've got the thermo fans running from the stock EA radiator thermo switch.  Recently I've been thinking that it would be more beneficial to have the ECU operate the thermo fans rather than letting the radiator potentially get hotter than the ECU wants it to be before the fans kick in.

Anyone done this with their conversion(s)?

 

Here's a couple of pics of my ride and conversion:

 

 

Regards

Bennie

[presslab]

I've done this on my EJ20G, which has two fan speeds, so a little different.

 

http://www.ultimatesubaru.org/forum/topic/127006-radiator-fan-ej-swap-between-engine-and-radiator/

 

http://www.ultimatesubaru.org/forum/topic/127644-my-ea82t-ej20g-conversion/

[Gloyale]

I did it with all mine too

 

using a standard Bosch type relay it would be like this

 

Batt+  power = 30

 

12v out to fan = 87

 

Ig. switched power + = 85

 

ECU fan trigger (ground) = 86

 

I personally like using regular suby relays myself.  B ut the Bosch # code makes explaining the circuit easy if you are familiar with it.

[el_freddo]

Thanks Goyale, I'm familiar with the bosch horn relays and their coding.

So now I just need to source the wire from the ECU - anyone happen to know which wire it is for a 1991/1992 legacy EJ22?  The page I used to get the wiring diagram from has disappeared which is very frustrating!

Also while we're on the topic of wiring, I'm looking at getting my AC sorted.  I remember an "AC relay cut" wire - do I need to hook some wire from the AC into the ECU so the ECU knows the AC is on and loading the engine at idle?

Cheers

Bennie

[Gloyale]

Thanks Goyale, I'm familiar with the bosch horn relays and their coding.

 

So now I just need to source the wire from the ECU - anyone happen to know which wire it is for a 1991/1992 legacy EJ22?  The page I used to get the wiring diagram from has disappeared which is very frustrating!

 

Also while we're on the topic of wiring, I'm looking at getting my AC sorted.  I remember an "AC relay cut" wire - do I need to hook some wire from the AC into the ECU so the ECU knows the AC is on and loading the engine at idle?

 

Cheers

 

Bennie

 

ECU fan wire will be a White/blue wire that originally went thorugh a diode and became red/blue

 

A/C cut not really needed but could be wired in.  Don't know the wire colors though.  Might be Blue/white IIRC???

[presslab]

To hook up the AC for idle compensation is pretty easy, but not necessary.  Without it the idle will dip a fair bit when AC kicks on but it won't stall.  This isn't "AC cut" though; that is meant to cut off the AC when full throttle for more power.  I hooked this up on my turbo conversion and it helps the turbo lag immensely.  I haven't done it on the Vanagon EJ25 conversion, I just turn off the AC when I'm hitting big grades or expect to pass.

 

If you want "AC cut" to work the AC input is needed but that's the easy part.  You also need to do a little rewiring and change the normally closed relay for a normally open one.  There is a junction of 3-4 blue/yellow wires IIRC and one of them needs to be unhooked and connected to the ECU.  This allows the ECU to control the relay running the AC system.

[el_freddo]

How do I tell the ECU to turn the thermos on when I've got the AC on?

And I found some wiring diagrams from numchux's website.  Just google subaru EJ wiring diagram and he'll be in there somewhere - maybe even throw his name into the search

Cheers

Bennie

[presslab]

The easiest is to leave the original AC wiring in place and hook the new relay up in parallel, this way either the ECU or the AC will turn it on.

 

If you want to go through the ECU, I believe the AC input is the red/blue wire. Be sure to disconnect the original thermoswitch from the radiator.

 

However if the ECU input is used, but not the cut relay, the idle might surge oddly when the AC turns on/off. The ECU input is more a request to the ECU for AC, and the ECU will normally turn the compressor on at it's leisure. Without the cut relay this could create weird idle fluctuations.

[Gloyale]

I ran a jumper jumper from the original A/C fan relay (EA's weren't ECU controlled)

 

It's the yellow wire on the outer of the 2 A/C relays (The other is the relay for the Clutch power IIRC)

 

When the A/C is on, that relay will provide ground to that yellow wire......which is tied to the OE fan switch wire at the radiator.

 

Just tap it and run that wire over to your new fan relay and tie it to the same pin that the ECU trigger is on.  A diode wouldn't hurt but not needed i don't think.

 

 

Press, I don't think the EJ ECU controlled the compressor.....other than the cutout feature that is.  The regular cycling of the Compressor is controlled by the thermostat in the Evap core, and the pressure switches.  Not postive.

 

 

But on another note there is a mod that needs done up under the glovebox, to eliminate the "pulse relay"  i.e. belt protection system.  This is assuming a Hitachi system.  It would be good to get info from the OP on that.

 

BUt yeah, I replaced the Pulser relay with a standard relay that simply completes ground for the Compressor circuit whenever the Evap thermo is closed, and the A/C or Defrost switch is pressed.  I actually want to relocate the microswitch on the ducting to be able to use ONLY for A/C not defrost.

 

El Freddo, any chance you know which A/C???

[presslab]

With the AC cut relay hooked up, the compressor will turn on about a half second after pushing the AC button on the dash.  I guess it's this way so the ECU can synchronize the IAC and the compressor solenoid, so rather than reacting to the compressor turning on it can do the two simultaneously so there isn't a hiccup in the idle.

 

Also I read that the ECU will cut off the AC when the engine is overheating; a nice feature too.

[el_freddo]

I ran a jumper jumper from the original A/C fan relay (EA's weren't ECU controlled)

 

It's the yellow wire on the outer of the 2 A/C relays (The other is the relay for the Clutch power IIRC)

 

When the A/C is on, that relay will provide ground to that yellow wire......which is tied to the OE fan switch wire at the radiator.

 

Just tap it and run that wire over to your new fan relay and tie it to the same pin that the ECU trigger is on.  A diode wouldn't hurt but not needed i don't think.

 

 

El Freddo, any chance you know which A/C???

 

Hmmm... I can't picture that in my head with the yellow wire and where it gets tied into etc  I've got this setup in my L for river crossings and hot weather driving on sand or during hill climbs:

 

 

So in theory I take the ECU trigger and hook that into the back of my switch?  What sort of diode would I need to protect the ECU, I would like to have that sort of protection!

 

As for the type of AC I've got, I think it's a Denso compressor - it certainly has never had the tab hanging out over the fan belts with that black box on it like every other L series I've come across.  I'll have to check the compressor to be sure it's a Denso, shouldn't be hard to do as it's living on my bench at the moment!

 

With the AC cut relay hooked up, the compressor will turn on about a half second after pushing the AC button on the dash.  I guess it's this way so the ECU can synchronize the IAC and the compressor solenoid, so rather than reacting to the compressor turning on it can do the two simultaneously so there isn't a hiccup in the idle.

 

Also I read that the ECU will cut off the AC when the engine is overheating; a nice feature too.

 

So if I've got this straight:  Hook up the AC input wire to the ECU from the AC dash switch and wire in a normally closed relay so that the ECU can short the relay circuit and cut the power to the AC compressor/system?  If so, that relay would look something like this (using the horn relay code):

 

Normally closed relay:

Power from AC switch = 30

"Other side" of the AC switch wiring to the compressor/AC system etc = 87

Ignition switched power (positive) = 85

ECU AC relay cut wire (Plug F47, pin 22) = 86

 

At the same time have the AC on input wired in from the switch before the above relay - this will have the AC switch tell the ECU the AC is on, even when the ECU AC cutout relay is in play.  Have I got this correct?

 

Then the last piece to the puzzle is to wire in the thermo fan relay/trigger wire - hook into the yellow/black wire on the back of my switch ("auto mode") with a diode to protect the ECU so I can keep the radiator thermo switch in play.  This setup should have the AC pressure switch already wired into the factory thermo wiring so no need to hook the ECU into this - but looking at the wiring diagram the EJ system has it the same, just that the ECU triggers it instead of a thermo switch in the radiator.

 

It's late over here, I've had a big day but I hope I've got my head around it - that's what I love about doing wiring conversions - get your head around it then it all falls into place and just becomes "easy" next time!

 

I also hope I haven't blown anyone's mind on this either!  I've really enjoyed the reading with the last couple of posts thanks to Goyale and Presslab.  I'm hoping you can confirm I've got his right, and if not, then correct my error or show a wiring diagram I can view.  I believe I've got it all sorted correctly though.

 

Regards

 

Bennie

 

[el_freddo]

Ok an update:

 

I've hooked up the ECU thermo fan trigger wire into the "auto" mode of the above switch diagram without a diode - it works without issue.  I found it interesting that the factory L series sensor trips in earlier than the ECU trigger wire does - but this was only on a warm up cycle in the driveway so things could be different when onroad with the ECU not triggering fans at speed etc.

Either way it works.

 

The AC idle up works a treat too.  I've gone with HyChill and the idle up is a bit much for this gas as from what I've read it doesn't work the compressor as hard for the same result as r134a.  Its awesome.  At idle my tacho needle sits at about 1000 rpm (I think I need to look into the throttle position sensor's settings) without AC on, when the idle up kicks in it sits at about 1150ish revs...

The cutout is yet to be sorted, I'm chasing which wire is responsible for turning the system on from the switch - but I could probably just run ignition power to the other side of the relay to do the same thing.

While I was at all this wiring I also installed a Gen2 or Gen1 Series 2 alternator - a greeny square plug unit - much better/stable/higher voltage output compared to the old round plug alternator.  Both round plugs I've run have struggled to maintain a charge voltage of 14 volts.  This "new" alternator puts out 14.3v in just about all situations even when I've got everything on that I can possibly load it up with.  Very happy.

Cheers

Bennie