2010 Legacy 2.5I AC Compressor bypass

It seems the wizards at Subaru decided to use a clutchless variable ac compressor on the 2010's. Meaning if the compressor seized (which mine did at 97k miles) the serpentine belt would burn up and break, leaving the car with no ALT or PS for the short run, dead alongside the road in the long run. You would think there would be a shear pin or something. If there is, mine didn't shear.

 

Unfortunately, It's not a simple as unplugging the electric clutch to bypass the AC. It doesn't have one.

 

Hopefully, this helps someone stuck in the same bind. This is a pricey compressor and this may be a help in the short run to keep you on the road until you can fix it correctly.

 

I took the old belt and cut it to the length I needed to bypass the AC pulley. Turns out its a 40.5 in or 1030mm length. I used the Duralast 405K6. This is routed from the PS pump, over the ALT, inside the idler, around the crank pulley, inside the tensioner and back to the PS pump. This keeps the rotation of all the pulleys correct. And the belt is only $12

 

The stock 6 rib belt will catch the upper alternator bolt while turning unless you trim it because you are routing it differently. I used a razor and cut the belt in half, 3 ribs, and it clears the bolt. The car runs and drives fine. No squealing. You might be able to find a belt made 3 ribs wide if you ask for it.

 

**Note this is not meant to be a permanent fix, but it will get you back on the road until you can get a new compressor**

 

If someone has a better solution, please share. I could not find one.

Interesting info, thanks for taking the time!

 

I've had variable displacement compressors in other cars and thankfully never had one seize up. Mostly the variable displacement control valve quits working and the compressor doesnt compress anymore.

 

They usually still have clutches though. Will take a look at mine next time the hood is up.

There is definitely a clutch, otherwise it would work all the time even when the AC was off, sounds like your clutch seized as well as the compressor.

My understanding is it uses an ecm actuated wobble plate inside the compressor to change the stroke of the pistons to modulate the refrigerant pressure. It was new for 2010 in the legacy. It spins all of the time. AC on or not.

 

It’s just a pulley on the front of the compressor with a pressed rubber insert. No electrical connections at all. If I’m wrong ang there is a way to make it freewheel, please tell me. I’d love to put the right belt on it.

 

I found this in another forum explaining how it works. Stupid if you ask me. Now I’m stuck needing a $600 compressor, even if I don’t want ac.

 

https://www.subaruoutback.org/forums/66-problems-maintenance/294601-when-did-subaru-start-using-clutchless-ac-compressors.html

Depending on the compressor model you may be able to replace its pulley for one with a clutch.

 

You'll have to pull down and reinstall though.

 

Is a junkyard compressor or an ebay special not an option? Havent looked yet but I am thinking they wouldnt reach $200?

 

EDIT: Oh and the variable displacements I've seen do work that way but they still usually have clutches.

Edited October 21, 2018 by Scubaboo

Definitely will be a used one. Looks like they are out there for about $100.

 

$600 Orem, and $375 reman. Plus the condenser since I’m sure this sent metal pieces downstream when it grenaded.

 

Problem for me is the car would Be a doorstop while I wait for the parts. I had to find a way around it, a temporary fix so I can use the car to get to work. Really stupid design not to have a shear pin or something to let it freewheel if it seizes.

 

I hope it helps someone else who is in a bind, it worked.

replace it or remove it. chances are you are also going to need a new condenser as metal parts from the compressor are most likely in it.

Used Compressor and AM condenser are enroute. Should be here this weekend. $70 for the condensor and $60 for the used compressor. ebay is a wonderful thing!

 

300+ miles and My little belt bypass is still holding up!

 

Thoughts on how much compressor oil I should be adding? I'm replacing the compressor (used), condenser (new AM), and flushing AC line between the two to make sure there are no bits of metal from the compressor grenading. Underhood only says ND8 oil, but no quantity.

drain old oil out of parts, add same amount of new oil if compressor does not have oil in it. if compressor does, add amount of oil that came out of condenser.

Replaced the AC compressor and condenser today.

 

A couple of learnings:

 

The AC condenser can be removed without removing the radiator and fans fairly easily. Removing the upper brackets tilt the rad back and the condenser will fit out through the top. You can remove the 10mm bolts in the front and leave the mounting brackets for the condenser attached to the rad support.

 

Before you begin, buy a couple packs of the 1/4 and 3/8 plastic pop rivets. On my 2010 six cracked in the grille, rad support upper trim and serpentine belt cover removing them. It will save you a trip to the auto parts store when you put it back together.

 

You can remove the compressor without removing the bracket. There are four 12 mm bolts on the right side. The bottom rear can be a bear, a longer 12mm box wrench is the ticket, more leverage the better. A ratcheting wrench will speed it out once you break it loose. It's too tight a space for a socket

 

The system takes 15 oz of R134 so plan accordingly. I used PAG 46 compressor oil. I added 5 oz replacing the compressor and condenser by pouring it directly into the high-pressure hose and letting it run down into the condenser. I added 1 oz to the low side hose so the compressor would not start dry. That was a guess on about 75% of the system capacity. Compressor didn't blow up so I must be close.

 

Lastly, while recharging this system with this stupid variable compressor, keep in mind the ECM is controlling the cycling pressures and there is no clutch to switch on and off, so when it's 42 degrees out you may not be able to get the system to build pressure. Oddly it still took just about 15 oz of R134, but I only had 60 psi on the high side gauge no matter what I did. Not an expert on this but my research seems to indicate the ECM knows its cold and basically shuts the pressures down.

 

Hope that helps

It may have more to do with the pressure coming back from the evaporator/the ability of the system to absorb heat from the interior. At 40°F the ambient air is as cold or colder than the "conditioned" air, so not much thermal energy to transfer.

 

Glad you got it sorted out and taught us a little about our cars along the way! Thank you.

It may have more to do with the pressure coming back from the evaporator/the ability of the system to absorb heat from the interior. At 40°F the ambient air is as cold or colder than the "conditioned" air, so not much thermal energy to transfer.

 

Glad you got it sorted out and taught us a little about our cars along the way! Thank you.

 

Thanks. It could be it's just too cold I suppose.

 

About 300 miles on the repair and no issues, no strange noises, etc. Still, don't know if the AC works lol, been cold up here in NE PA.

Well if finally got warm enough here in the northeast for the ac to function. And it doesn’t.

 

I have a question for any of the Subaru techs that may be on the forum.

 

SSM 3 and the service manual has an ac compressor break in procedure for replacing the compressor. I replaced it used so I didn’t do it. Do I need to? Does the system need to relearn the different compressor?

 

It’s computer controlled so I don’t know if there is an ID or something in it the system needs to learn.

Well if finally got warm enough here in the northeast for the ac to function. And it doesn’t.

 

I have a question for any of the Subaru techs that may be on the forum.

 

SSM 3 and the service manual has an ac compressor break in procedure for replacing the compressor. I replaced it used so I didn’t do it. Do I need to? Does the system need to relearn the different compressor?

 

It’s computer controlled so I don’t know if there is an ID or something in it the system needs to learn.

The peripheral accessories aren't BIU controlled so they dont need to be programmed to work, they are either on or off based on voltage from the wiring harness input to them. If a compressor fails its usually good practice to replace the expansion valve and completely flush the system. I personally would have also replaced the condenser for good measure.

 

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The peripheral accessories aren't BIU controlled so they dont need to be programmed to work, they are either on or off based on voltage from the wiring harness input to them. If a compressor fails its usually good practice to replace the expansion valve and completely flush the system. I personally would have also replaced the condenser for good measure.

 

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I did replace the condenser when I replaced the compressor used.

 

On this car, with the variable AC compressor, the AC is absolutely computer controlled. I was just wondering if anyone knew before I dug into it.

I did replace the condenser when I replaced the compressor used.

 

 

 

On this car, with the variable AC compressor, the AC is absolutely computer controlled. I was just wondering if anyone knew before I dug into it.

You are confusing computer-controlled with can-bus.

 

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Edited April 21, 2019 by FLlegacy

You are confusing computer-controlled with can-bus.

 

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It’s not ecm controlled it has its own control module with its on diagnostic codes

 

 

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It’s not ecm controlled it has its own control module with its on diagnostic codes

 

 

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Some hvac control modules have that but I dont recall the compressor being a direct part of that system. That is the actual control panel in the interior of the car. I can look in the FSM when I get back to my laptop.

 

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I checked the AC system with SSM3 - no codes present.

 

I attempted to command the system on, commanding the compressor variable valve solenoid to 100% and SSM gave me an error that the system was in 'protect mode'

 

SSM System pressure shows .11 Mpa - or about 16psi so it has some R134 in it. But I thinks that is way low. I'm guessing its why I can't command it on.

 

I'll have to verify that reading with the manifold gauges. Hitting the high pressure valve quick with a small screwdriver it sure seems like there is a hell of a lot more pressure in it than 16 psi. Might be the pressure switch is faulty. At rest, the system should be ~80 psi, correct?

 

It's still cool here in the NE so I'll fool with it next weekend.

According to the fsm replacing the compressor, or any part of the ac system doesnt require programming. The command module which displays it's own unique DTCs is the ac control unit in the dash.

 

Attached is the pressure check chart from the FSM.

 

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AC pressure 2010 legacy.pdf

Edited April 22, 2019 by FLlegacy

If you replace it new, you need to do this procedure with SSM. What I originally asked was would this be required with a used compressor, not knowing if it somehow had to learn the compressor, kind of like an idle relearn.

 

The question is moot at this point, because the system pressure it sees is so low, I can't run it anyway.