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  View original topic: Subaru / Vanagon A/C wiring
monkeyscoot Sat Nov 14, 2020 10:35 am

Hey,

I've had a Subaru in the back of my vanagon for a few years now, but never had the A/C hooked up as I live in the UK I never really saw the need for it.

I've finally got around to plumbing it all in, I've got a Carat with the long centre tunnel down the middle.

Has anyone got any information on what needs to be done wiring wise? My plan is to leave the wiring in the side panel in tact and use the trigger wire from the vanagon system to power the compressor. What has to be done R.E the subaru ECU triggers etc?

I've begun renewing all of the hoses/condenser etc and ended up with a new trinary switch, so I've ended up with 3 different wire colour setups... What's usually done with these to get an aftermarket switch working with the vanagon setup?






Any help would be greatly appreciated !

[email protected] Sat Nov 14, 2020 10:41 am

basically all you need to do is put the signal wire from the van (12v+ when you turn the a/c on) to the subaru harness for a/c command. this will raise the idle and trigger the compressor

you'll need to know which pin on your ECU does this

monkeyscoot Sat Nov 14, 2020 11:04 am

[email protected] wrote: basically all you need to do is put the signal wire from the van (12v+ when you turn the a/c on) to the subaru harness for a/c command. this will raise the idle and trigger the compressor

you'll need to know which pin on your ECU does this

That's basically where my thinking was at, so the output from the vanagon relay will split to power the compressor and also go to the ECU ?

I have 2 connectors / 3 wires on my Compressor, was wondering what the others are used for ?

It's from an EJ25 2003

EDIT:






So these are the two connectors that plug into my compressor.

I've got a single pin black connector that will connect to the magnetic clutch

and a two pin blue connector, which I believe is the thermal protector?

Is this two pin connector required? or is the system protected by the trinary switch, so no need for the thermal cutout?

Cheers

pbrown Sat Nov 14, 2020 2:33 pm

I can't answer your question regarding the thermal protector. But is does seem that you would need the short the pins on the two pin connector to make the clutch engage if you omit it.

I'm working on the same right now. I have a 2003 EJ25 and am getting my A/C sorted. I can't believe that I'm working on an A/C system in 40F degree temps.

Good luck.

[email protected] Sat Nov 14, 2020 3:57 pm

post a photo of your compressor. subaru used a couple styles.

EDIT

ok, you have the goofy 3 wire.

i have not had the privilege of running a 3 wire in a swap. i'd have to log in to read up more on the diagrams, but iirc the thermal deal was used on some compressors and not others.

the black single bullet connector is what trips the clutch. in a single wire a/c compressor you put 12v to that, and it ties into the ecu (A17 in your photo) to bump the idle.

now, here is the rub...

with the older systems that cycle the compressor and you wire it this way, you may get a kick when the compressor cycles. i like to wire it so the ECU doesn't see the cycling, meaning that when the a/c is on, the ecu thinks it's on all the time and doesn't cycle with the compressor.

to do this, take the + to your pressure switch and piggy back off of that. from your other terminal on the pressure switch, run THAT to the compressor. you'll still feel the clutch cycle, but it won't be a kick from a mule if the engine has idled down.


the idea is to keep the condenser fan/radiator fan still ON even when the compressor is off and keep that ECU 200 rpm idle bump while the fan(s) are running

i've seen some people wire it so all the fans and the compressor kick in and out at the same time...talk about bucking...
hope that makes sense...

monkeyscoot Sun Nov 15, 2020 1:30 am

[email protected] wrote: post a photo of your compressor. subaru used a couple styles.

EDIT

ok, you have the goofy 3 wire.

i have not had the privilege of running a 3 wire in a swap. i'd have to log in to read up more on the diagrams, but iirc the thermal deal was used on some compressors and not others.

the black single bullet connector is what trips the clutch. in a single wire a/c compressor you put 12v to that, and it ties into the ecu (A17 in your photo) to bump the idle.

now, here is the rub...

with the older systems that cycle the compressor and you wire it this way, you may get a kick when the compressor cycles. i like to wire it so the ECU doesn't see the cycling, meaning that when the a/c is on, the ecu thinks it's on all the time and doesn't cycle with the compressor.

to do this, take the + to your pressure switch and piggy back off of that. from your other terminal on the pressure switch, run THAT to the compressor. you'll still feel the clutch cycle, but it won't be a kick from a mule if the engine has idled down.


the idea is to keep the condenser fan/radiator fan still ON even when the compressor is off and keep that ECU 200 rpm idle bump while the fan(s) are running

i've seen some people wire it so all the fans and the compressor kick in and out at the same time...talk about bucking...
hope that makes sense...

Thank you all for your inputs, The knowledge in this place is amazing haha.

I believe I understand where you're coming from ..

So in theory the compressor cutout on the Trinary switch can still be wired straight to the compressor clutch ( NOT through the ECU )

And the ECU will get it's signal either from the fan side of the Trinary switch or basically just the " A/C is on" live from the a/c switch etc

So whenever the a/c is set to be running, whether the compressor is running or not the idle should be bumped 200rpm which should stop the bucking ?

Thanks for the heads up, as that would've have bugged me if the van kicks like a mule every cycle.

I guess the thermal cutout will have to be a sick it and see jobbie, can't seem to find much info on it. So I'll get everything plumbed in / wired up and see if it works I guess !

[email protected] Sun Nov 15, 2020 9:28 am

monkeyscoot wrote:
Thank you all for your inputs, The knowledge in this place is amazing haha.

I believe I understand where you're coming from ..

So in theory the compressor cutout on the Trinary switch can still be wired straight to the compressor clutch ( NOT through the ECU )

And the ECU will get it's signal either from the fan side of the Trinary switch or basically just the " A/C is on" live from the a/c switch etc

So whenever the a/c is set to be running, whether the compressor is running or not the idle should be bumped 200rpm which should stop the bucking ?


yes, exactly. you'll still get a small "bump" or hiccup when the compressor comes on but not nearly as bad as it would be trying to raise the RPM's, fire the compressor and fans all at once.

this will really help more in around town driving. when the compressor kicks in at speed, you'll just feel it a tiny bit.

starting in about 2008 in the european car world they went to VDC's or variable displacement compressors... here is a article

https://axleaddict.com/auto-repair/Variable-Displacement-Compressors

basically they had a solenoid that pissed in more or less refrigerant depending on demand, and the clutch stayed engaged or the compressors were just clutchless. this got rid of any bump because the clutch never kicked in (so to speak) flow/pressure was regulated thru the valve



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